Tropical Storm Florence

Tropical Depression Florence Rainfall Forecast 0500 Hours September 17 2018
Tropical Depression Florence Rainfall Forecast 0500 Hours September 17 2018

NWS Weather Prediction Center College Park MD 1100 AM EDT Mon Sep 17 2018

 (see 24 videos below)

SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...38.5N 82.9W
ABOUT 240 MI...385 KM W OF CHARLOTTESVILLE VIRGINIA
MAXIMUM SUSTAINED WINDS...25 MPH...35 KM/H
PRESENT MOVEMENT...NE OR 40 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES

DISCUSSION AND OUTLOOK

At 1100 AM EDT (1500 UTC), the center of Tropical Depression Florence was located near latitude 38.5 North, longitude 82.9 West. The depression is moving toward the northeast near 15 mph (24 km/h) and is forecast to become extratropical late today while accelerating to the east-northeast.

Maximum sustained winds are near 25 mph (35 km/h) with higher gusts. Little change in strength is forecast until the low moves into the western Atlantic by early Wednesday.

The estimated minimum central pressure is 1008 mb (29.77 inches).

HAZARDS AFFECTING LAND

RAINFALL: Florence is expected to produce heavy to excessive rainfall over the next couple of days. Portions of the Mid Atlantic states west of Interstate 95 into southern New York and southern New England are expected to receive an additional 2 to 4 inches of rain…with isolated maximum amounts of 6 inches possible. For more information on rainfall totals please see the Storm Summary available at www.wpc.ncep.noaa.gov/discussions/nfdscc4.html TORNADOES: A couple of tornadoes remain possible from northeast South Carolina and eastern/central North Carolina into parts of Virginia, western Maryland, and southern Pennsylvania through today.

NWS Weather Prediction Center College Park MD 1100 AM EDT Sun Sep 16 2018

SUMMARY OF WATCHES AND WARNINGS IN EFFECT: There are no coastal watches or warnings in effect.

Flash flood warnings are currently in effect across a large portion of southeastern North Carolina and portions of far northeastern South Carolina. Flash flood watches are in effect across much of North Carolina…northern South Carolina and portions of Southwest Virginia.

DISCUSSION AND OUTLOOK

At 1100 AM EDT (1500 UTC), the center of Tropical Depression Florence was located near latitude 34.0 North, longitude 81.8 West. The depression is moving toward the north-northwest near 10 mph (17 km/h) and this motion is expected to continue through the day on Sunday. Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Some weakening is forecast during the next 48 hours. The estimated minimum central pressure is 1002 mb (29.59 inches).

HAZARDS AFFECTING LAND

RAINFALL: Florence is expected to produce heavy and excessive rainfall in the following areas… Southeastern…Central and western North Carolina…far northern South Carolina into far southwest Virginia… Southeastern North Carolina and far northeast South Carolina: Additional 3 to 6 inches of rain…with isolated maximum of 8 inches possible…with storm total accumulations of 30 to 40 inches likely. These rainfall amounts will produce catastrophic flash flooding and prolonged significant river flooding. Central and Western North Carolina…far northern South Carolina and far southwest Virginia: Additional 5 to 10 inches of rain, with storm total accumulations of 15 to 20 inches likely. These rainfall amounts will produce flash flooding and an elevated risk for landslides in western North Carolina and far southwest Virginia. West-central Virginia: 2 to 4 inches, isolated 6 inches. This rainfall will result in flash flooding and potentially lead to some river flooding. For more information on rainfall totals please see the Storm Summary available at www.wpc.ncep.noaa.gov/discussions/nfdscc1.html

TORNADOES: A few tornadoes remain possible across southeast North Carolina and northeastern South Carolina today and tonight.

FORECAST POSITIONS AND MAX WINDS

INIT  16/1500Z 34.0N  81.8W   30 KT  35 MPH - Tropical Storm (Saluda, SC)
 12H  17/0000Z 35.3N  82.8W   25 KT  30 MPH - Tropical Storm (Brevard, NC)
 24H  17/1200Z 37.8N  83.3W   20 KT  25 MPH - Tropical Storm (Cannel City, KY)
 36H  18/0000Z 39.7N  80.5W   15 KT  15 MPH - Tropical Storm (Littleton, WV)
 48H  18/1200Z 40.7N  76.1W   15 KT  15 MPH - Tropical Storm (New Philadelphia, PA)
 72H  19/1200Z 42.3N  64.3W   35 KT  40 MPH - Tropical Storm (ESE Shelburne, Nova Scotia, Canada)
 96H  20/1200Z 44.2N  50.4W   35 KT  40 MPH - Tropical Storm (ESE St. John's, Newfoundland, Canada)
120H  21/1200Z 46.1N  38.2W   40 KT  45 MPH - Tropical Storm (ESE St. John's, Newfoundland, Canada)

NWS National Hurricane Center Miami FL 500 AM EDT Sun Sep 16 2018

Surface observations indicate that there are no longer any sustained tropical-storm-force winds as the center of Florence  has moved farther inland over South Carolina. Therefore, the system is being downgraded to a tropical depression at this time. Maximum winds are estimated to be 30 kt. Continued gradual weakening is likely, and the numerical guidance suggests that the cyclone will be disorganized enough to become a remnant low in 36 hours or so. In 72 hours, global models indicate that the system will become an extratropical cyclone, with some strengthening due to baroclinic processes as it moves over the Atlantic in 3-5 days. This scenario is very similar to that from the previous advisory.

The forward speed of Florence has increased somewhat early this morning and the motion is now near 280/7 kt. The high pressure system that has been blocking the forward progress of Florence is predicted to slide eastward and southeastward during the next day or so. As a result, over the next couple of days, Florence is expected to move northwestward, northward, and then north-northeastward around the periphery of the high. Later in the forecast period, Florence should accelerate east-northeastward in the mid-latitude westerlies. The official track forecast is similar to the previous one and close to the dynamical model consensus. This will be the last advisory issued by the National Hurricane Center on Florence. Future information on Florence can be found in Public Advisories issued by the Weather Prediction Center beginning at 11 AM EDT, under AWIPS header TCPAT1, WMO header WTNT31 KWNH, and on the web at https://www.wpc.ncep.noaa.gov.

Key Messages:

1. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into west-central Virginia and far eastern West Virginia through early this week, as Florence continues to move slowly inland. In addition to the flash flood and flooding threat, landslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia.

2. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 33.8N  81.4W   30 KT  35 MPH - Tropical Storm (Pelion, SC) 
 12H  16/1800Z 34.7N  82.5W   30 KT  35 MPH - Tropical Storm (Piedmont, SC) 
 24H  17/0600Z 36.7N  83.6W   25 KT  30 MPH - Tropical Storm (Calvin, KY) 
 36H  17/1800Z 38.7N  82.6W   20 KT  25 MPH - Tropical Storm (Willow Wood, OH) 
 72H  19/0600Z 42.0N  68.0W   30 KT  35 MPH - Tropical Storm (ESE Provincetown, MA) 
 96H  20/0600Z 43.5N  55.0W   35 KT  40 MPH - Tropical Storm (ESE Sherbrooke, Nova Scotia, Canada) 
120H  21/0600Z 46.0N  40.0W   40 KT  45 MPH - Tropical Storm (ESE St. John's, Newfoundland, Canada)

NWS National Hurricane Center Miami FL 1100 PM EDT Sat Sep 15 2018

Tropical Storm Florence’s  center continues to trudge slowly westward across South Carolina, but heavy rainbands are still streaming inland from the ocean across extreme southeastern North Carolina. The NOS station at the Johnny Mercer Pier in Wrightsville Beach in the vicinity of these rainbands is the lone observing station that has still been reporting sustained tropical-storm-force winds, and based on the most recent observations, Florence’s maximum winds are estimated to be 35 kt.

Florence is expected to weaken to a tropical depression within the next 6-12 hours, with the global model fields showing winds decreasing below 35 kt near the coast very soon. Continued weakening is anticipated while Florence moves farther inland, and it is likely to become a remnant low in about 36 hours when its circulation becomes less defined. Florence is then expected to become a strengthening extratropical low between days 3 and 5 when it exits the Northeast U.S. coast and moves out to sea.

The initial motion is still very slow toward the west, or 275/3 kt. A mid-level ridge across the Upper Midwest and Great Lakes is currently blocking Florence from making much headway, but that feature is expected to slide eastward to the western Atlantic during the next 24 hours. This should allow Florence to recurve and accelerate across the Ohio Valley and the northeastern U.S. during the next 3 days, and then accelerate further toward the east-northeast over the Atlantic Ocean on days 4 and 5. The new NHC track forecast is essentially an update of the previous one and is close to the various model consensus aids.

Key Messages:

1. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into west-central Virginia and far eastern West Virginia through early next week, as Florence moves slowly inland. In addition to the flash flood and flooding threat, landslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia.

2. Tropical storm conditions will continue along the coast within the tropical storm warning area and also well inland across portions of South Carolina and North Carolina overnight.

3. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0300Z 33.7N  80.5W   35 KT  40 MPH - Tropical Storm (Rimini, SC) 
 12H  16/1200Z 34.3N  81.6W   30 KT  35 MPH - Tropical Storm (Newberry, SC)
 24H  17/0000Z 35.8N  83.2W   25 KT  30 MPH - Tropical Storm (Cosby, TN)
 36H  17/1200Z 37.8N  83.2W   20 KT  25 MPH - Tropical Storm (Harper, KY)
 48H  18/0000Z 39.2N  81.3W   20 KT  25 MPH - Tropical Storm (Petroleum, WV) 
 72H  19/0000Z 41.5N  71.5W   25 KT  30 MPH - Tropical Storm (North Kingstown, RI)
 96H  20/0000Z 43.0N  59.5W   35 KT  40 MPH - Tropical Storm (ESE Lunenburg, Nova Scotia)
120H  21/0000Z 45.5N  47.0W   40 KT  45 MPH - Tropical Storm (ESE St. John's, Newfoundland)

NWS National Hurricane Center Miami FL 800 PM EDT Sat Sep 15 2018

Tropical Storm Florence  – CENTER OF FLORENCE DRIFTING WESTWARD OVER SOUTH CAROLINA…

FLASH FLOODING AND MAJOR RIVER FLOODING OCCURRING OVER A SIGNIFICANT PORTION OF THE CAROLINAS

DISCUSSION AND OUTLOOK

At 800 PM EDT (0000 UTC), the center of Tropical Storm Florence was located by NOAA Doppler radars near latitude 33.6 North, longitude 80.1 West. Florence is moving toward the west near 2 mph (4 km/h), and a slow westward motion is expected to continue through tonight. A turn toward the west-northwest and northwest is expected on Sunday. Florence is forecast to turn northward through the Ohio Valley by Monday.

Surface observations indicate that maximum sustained winds remain near 45 mph (75 km/h) with higher gusts, mainly to the northeast and east of the center in heavy rainbands over water. Gradual weakening is forecast while Florence moves farther inland during the next couple of days, and it is expected to weaken to a tropical depression tonight or by Sunday morning.

Tropical-storm-force winds extend outward up to 150 miles (240 km) mainly to the east of the center near the coast and over water. Within the past hour or two, a sustained wind of 46 mph (74 km/h) with a gust to 59 mph (95 km/h) was reported at the Johnny Mercer Pier in Wrightsville Beach, North Carolina. A wind gust to 45 mph (72 km/h) was recently reported near Hartsville, South Carolina.

The estimated minimum central pressure based on nearby surface observations is 997 mb (29.44 inches).

HAZARDS AFFECTING LAND

STORM SURGE: Water levels along the coast of North and South Carolina are gradually receding. Some minor coastal flooding is still possible through Sunday. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: Florence is expected to produce heavy and excessive rainfall in the following areas… Southern and central portions of North Carolina into far northeast South Carolina…an additional 15 to 20 inches, with storm totals between 30 and 40 inches along the North Carolina coastal areas south of Cape Hatteras. This rainfall will continue to produce catastrophic flash flooding and prolonged significant river flooding. Remainder of northern South Carolina into western North Carolina and southwestern Virginia…5 to 10 inches, isolated 15 inches.

NWS National Hurricane Center Miami FL 500 PM EDT Sat Sep 15 2018

Tropical Storm Florence’s  center has continued its slow…and I do mean s-l-o-w… westward trek across eastern South Carolina, with little change in the overall structure of the wind field both overland and over water. NOAA WSR-88D Doppler weather radar data, surface observations, and a 1527Z ASCAT pass indicate that Florence is still producing a significant fetch of tropical storm force winds within and adjacent to the the two bands of convection that are currently located between the Cape Fear/Wilmington area and Bogue Inlet, North Carolina. The ASCAT pass contained numerous 40-45 kt wind vectors, and the NOAA NOS observing site at Johnny Mercer Pier in Wrightsville Beach, North Carolina, has been reporting sustained winds of 38-41 kt and gusts to 46-48 kt during the past few hours during the passage of light to moderate rain showers. Therefore, the initial intensity is being maintained at a conservative 40 kt for this advisory. The estimated central pressure of 997 mb is based on nearby surface observations across eastern South Carolina.

The initial motion remains 270/02 kt. The new 12Z model guidance remains in excellent agreement on a mid-level ridge currently to the northwest and north of Florence moving steadily eastward during the next 48 hours, which will keep the broad cyclone moving slowly westward to west-northwestward during that time. By 48 hours and beyond, the ridge is forecast to continue to shift eastward to near the northeast U.S. coast and weaken, which will allow Florence and its remnant circulation to move slowly northward into the mid-latitude westerlies by Tuesday. By days 3-5, the global models diverge on where and how fast Florence’s then extratropical circulation moves. Due to the significant spread in the guidance, the official forecast track lies close to the consensus model TCVA/TVCN and the previous advisory track forecast.

Florence’s inner-core convection and wind field will steadily weaken throughout the next 48 hours or so. However, the outer wind field and an associated band of deep convection in the eastern semicircle should continue to produce tropical-storm-force winds for another 12 hours or so over water and near the coast, with occasional strong wind gusts occurring over land. The official intensity forecast is close to an average of the Decay-SHIPS and LGEM, and the IVCN consensus intensity model guidance through 72 hours, and then follows a blend of the IVCN, HCCA, and FSSE consensus models at 96 and 120 hours when the post-tropical cyclone moves back over water and strengthens some due to baroclinic processes.

Although coastal storm surge flooding will continue to subside tonight and Sunday, torrential rainfall will continue to be a serious hazard associated with slow-moving Florence. More than two- and-a-half feet of rain has already fallen across portions of southeastern North Carolina, and more rain is still to come, which will cause disastrous flooding that will spread farther inland through the weekend.

Key Messages:

1. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into west-central Virginia and far eastern West Virginia through early next week, as Florence moves slowly inland. In addition to the flash flood and flooding threat, landslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia.

2. Water levels along the coast will gradually subside through Sunday.

3. Tropical storm conditions will continue along the coast within the tropical storm warning area and also well inland across portions of South Carolina and North Carolina today.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  15/2100Z 33.6N  79.9W   40 KT  45 MPH - Tropical Storm (Salters, SC)
 12H  16/0600Z 33.9N  80.9W   35 KT  40 MPH - Tropical Storm (Hopkins, SC)
 24H  16/1800Z 35.1N  82.6W   25 KT  30 MPH - Tropical Storm (Slater-Marietta, SC)
 36H  17/0600Z 37.0N  83.2W   25 KT  30 MPH - Tropical Storm (Big Laurel, KY)
 48H  17/1800Z 38.8N  82.1W   20 KT  25 MPH - Tropical Storm (Point Pleasant, WV)
 72H  18/1800Z 41.4N  74.5W   20 KT  25 MPH - Tropical Storm (Johnson, NY)
 96H  19/1800Z 43.3N  60.8W   30 KT  35 MPH - Tropical Storm (ESE Port Dufferin, Nova Scotia)
120H  20/1800Z 47.0N  47.0W   40 KT  45 MPH - Tropical Storm (E St. John's, Newfoundland)

NWS National Hurricane Center Miami FL 1100 AM EDT Sat Sep 15 2018

Florence  continues to creep slowly westward and weaken across eastern South Carolina. NOAA WSR-88D Doppler weather radar data indicate strong winds near 60 kt still exist between 3000-10000 ft within intense rainbands situated between the Cape Fear/Wilmington area and Bogue Inlet, North Carolina. Although those velocity values would typically correlate to 50-kt surface winds, those winds appear to be associated with small mesoscale circulations and possible supercell thunderstorms, and not the larger tangential wind field. In contrast, surface observations during the past couple of hours have only shown sustained winds of around 40 kt, so that is the intensity used for this advisory. The estimated central pressure of 995 mb is based on nearby surface observations across eastern South Carolina.

Radar data and surface observations indicate that Florence has turned more westward, and has slowed down even more, and the initial motion estimate is now 270/02 kt. The models remain in very good agreement that a mid-level ridge currently centered over the upper Midwest will slide eastward across the lower Great Lakes to near the northeastern U.S. during the next 48 hours. This feature is expected to steer Florence and its remnants in a general westward motion for the next 24 hours or so, followed by a turn toward the northwest on Monday. The ridge will continue to shift eastward and weaken, allowing Florence’s circulation to get caught up in the faster mid-latitude westerlies and accelerate toward the northeast on day 3 and toward the east-northeast on days 4 and 5 as an extratropical low pressure system. The new NHC track is similar to the previous advisory track, and lies near the consensus model TCVA/TVCN.

Florence’s inner-core convection and wind field will continue to weaken throughout the next 72 hours or so. However, the outer wind field and an associated band of deep convection in the eastern semicircle will likely produce sustained tropical-storm-force winds for another 12 hours or so, with some high gusts continuing until the band moves inland by late Sunday as per the latest the latest NOAA HRRR and other mesoscale model runs. More importantly, continued heavy rains will be produced by this band of convection, which will exacerbate the already catastrophic flooding that is occurring across much of southeastern North Carolina. The official intensity forecast closely follows the Decay-SHIPS model guidance and the intensity model IVCN through 72 hours, and then follows a blend of the IVCN, HCCA, and FSSE consensus models on days 4 and 5 when the post-tropical cyclone is forecast to strengthen due to baroclinic processes after moving over the relatively warm waters of the northwestern Atlantic Ocean.

Although coastal storm surge flooding will gradually subside today, especially after the midday high-tide period ends, extremely heavy rainfall will continue to be a serious hazard associated with slow-moving Florence. More than two feet of rain has already fallen across portions of southeastern North Carolina, and more rain is still to come, which will cause disastrous flooding that will spread inland through the weekend.

Key Messages:

1. Life-threatening storm surge will continue along portions of the North Carolina coast through today, and also along the Neuse and Pamlico Rivers in western Pamlico Sound, where rainfall and freshwater flooding will also contribute to high water levels. Dangerous storm surge could also affect portions of the northeast coast of South Carolina coast today.

2. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into west-central Virginia and far eastern West Virginia through early next week, as Florence moves slowly inland. In addition to the flash flood and flooding threat, landslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia.

3. Tropical storm conditions will continue along the coast within the tropical storm warning area and also well inland across portions of South Carolina and North Carolina today.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 33.6N  79.6W   40 KT  45 MPH - Tropical Storm (Nesmith, SC)
 24H  16/1200Z 34.4N  81.7W   25 KT  30 MPH - Tropical Storm (Joanna, SC)
 36H  17/0000Z 36.0N  82.8W   25 KT  30 MPH - Tropical Storm (Whitesand, TN)
 48H  17/1200Z 38.0N  82.9W   20 KT  25 MPH - Tropical Storm (Martha, KY)
 72H  18/1200Z 41.3N  76.5W   20 KT  25 MPH - Tropical Storm (Lungerville, PA)
 96H  19/1200Z 44.3N  63.4W   30 KT  35 MPH - Tropical Storm (ESE Sambro, Nova Scotia, Canada)
120H  20/1200Z 48.5N  49.0W   40 KT  45 MPH - Tropical Storm (ENE St. John's, Newfoundland, Canada )

NWS National Hurricane Center Miami FL 800 AM EDT Sat Sep 15 2018

LOCATION…33.6N 79.5W ABOUT 35 MI…55 KM W OF MYRTLE BEACH SOUTH CAROLINA

ABOUT 45 MI…70 KM SSE OF FLORENCE SOUTH CAROLINA

MAXIMUM SUSTAINED WINDS…50 MPH…80 KM/H

PRESENT MOVEMENT…W OR 260 DEGREES AT 2 MPH…4 KM/H

MINIMUM CENTRAL PRESSURE…989 MB…29.20 INCHES

DISCUSSION AND OUTLOOK

At 800 AM EDT (1200 UTC), the center of Tropical Storm Florence was located near latitude 33.6 North, longitude 79.5 West. Florence is moving toward the west near 2 mph (4 km/h), and a slow westward motion is expected to continue through today. A turn toward the west-northwest and northwest is expected on Sunday. Florence is forecast to turn northward through the Ohio Valley by Monday.

Radar data continue to indicate that the maximum sustained winds remain near 50 mph (80 km/h) with higher gusts in heavy rainbands over water. Gradual weakening is forecast while Florence moves farther inland during the next couple of days, and it is expected to weaken to a tropical depression by tonight.

Tropical-storm-force winds extend outward up to 175 miles (280 km) from the center. A sustained wind of 44 mph (70 km/h) with a gust to 51 mph (83 km/h) was recently reported at the Johnny Mercer Pier in Wrightsville Beach, North Carolina. A sustained wind of 43 mph (69 km/h) with a gust to 51 mph (83 km/h) was recently reported by NOAA Buoy 41013 at Frying Pan Shoals, North Carolina.

The estimated minimum central pressure based on nearby surface observations is 989 mb (29.20 inches).

 

NWS National Hurricane Center Miami FL AL062018 500 AM EDT Sat Sep 15 2018

Florence  is slowly weakening while its center remains inland over extreme eastern South Carolina. However, WSR-88D Doppler radar still shows some intense bands of convection over the eastern portion of the circulation, and these bands have been training over the coast of North Carolina overnight. Based on current Doppler velocities of 55-60 kt at around 5500 ft, the current intensity is set at 45 kt. The system should continue to weaken as it moves farther inland today, and it is anticipated that Florence will become a tropical depression tonight. The official intensity forecast is similar to the Decay-SHIPS model guidance through around day 3. By days 4 and 5, the post-tropical cyclone is forecast to strengthen somewhat due to baroclinic processes after moving off the New England coast and passing near southern Atlantic Canada.

Radar and satellite fixes indicate that Florence continues its west-southwestward motion at around 255/4 kt. A mid-level high pressure area to the northwest of Florence is forecast to shift to the north, northeast, and east of the cyclone over the next couple of days. As a result, Florence should turn northwestward and northward, and then north-northeastward through 72 hours. Late in the forecast period, the system is expected to accelerate east-northeastward in the mid-latitude westerlies. The official forecast is somewhat faster than the previous one at days 4 and 5 but is in good agreement with the latest global model runs.

Although coastal storm surge flooding will gradually subside today, extremely heavy rainfall will continue to be a serious hazard associated with slow-moving Florence. More than a foot of rain has already fallen across portions of southeastern North Carolina, and more rain is still to come, which will cause disastrous flooding that will spread inland through the weekend.

Key Messages:

1. Life-threatening storm surge will continue along portions of the North Carolina coast through today, and also along the Neuse and Pamlico Rivers in western Pamlico Sound, where rainfall and freshwater flooding will also contribute to high water levels. Dangerous storm surge could also affect portions of the northeast coast of South Carolina coast today.

2. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into west-central Virginia and far eastern West Virginia through early next week, as Florence moves slowly inland. In addition to the flash flood and flooding threat, landslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia.

3. Tropical storm conditions will continue along the coast within the tropical storm warning area and also well inland across portions of South Carolina and North Carolina today.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

 

FORECAST POSITIONS AND MAX WINDS

INIT  15/0900Z 33.6N  79.5W   45 KT  50 MPH - Tropical Storm (Nesmith, SC)
 12H  15/1800Z 33.6N  80.2W   40 KT  45 MPH - Tropical Storm (White Oak, SC)
 24H  16/0600Z 33.9N  81.3W   30 KT  35 MPH - Tropical Storm (Red Bank, SC)
 36H  16/1800Z 35.1N  82.4W   25 KT  30 MPH - Tropical Storm (Greer, SC)
 48H  17/0600Z 37.0N  83.5W   25 KT  30 MPH - Tropical Storm (Roark, KA)
 72H  18/0600Z 40.5N  80.0W   20 KT  25 MPH - Tropical Storm (Ross Township, PA)
 96H  19/0600Z 43.5N  68.0W   30 KT  35 MPH - Tropical Storm (ESE Portland, ME)
...POST-TROP/EXTRATROP

NWS National Hurricane Center Miami FL 1100 PM EDT Fri Sep 14 2018

Tropical Storm Florence – Although we lost data from the Wilmington, North Carolina, WSR-88D radar several hours ago, the radars from Raleigh and Columbia have clearly shown Florence’s center has moved into extreme eastern South Carolina. Reflectivities around the eye have been decreasing, but there are still some strong spiral bands moving from southeast to northwest across portions of southeastern North Carolina. Maximum Doppler velocities are 65-70 kt from 5000-7000 feet, and on this basis Florence’s maximum surface winds are estimated to be 55 kt.

Radar fixes indicate that Florence has turned west-southwestward and has an initial motion of 255/4 kt. A mid-level high centered near Iowa and Missouri is expected to slide eastward to the north of Florence over the next 48 hours, which should cause the storm to maintain a slow motion and gradually turn toward the west and northwest over the Carolinas. For this period, the new official forecast track has been shifted a bit southward to follow an overall trend in the model guidance, but this isn’t surprising given what some of the models were showing last night. After 48 hours, Florence is expected to get picked up by the mid-latitude westerlies, accelerating north and northeastward to the western Atlantic by day 5. The NHC track forecast is fairly close to the TVCN multi-model consensus and just a little south of the previous forecast beyond 72 hours.

Florence’s winds should continue to slowly decay as the center ambles farther inland, but enough of the circulation should remain over water to allow the cyclone to remain as a tropical storm for the next 24 hours or so. This thinking follows the global model fields of the GFS and ECMWF models. After 24 hours, most of Florence’s circulation should be inland, allowing the cyclone to weaken to a tropical depression and eventually degenerate into a remnant low over the Ohio Valley by day 3. The remnant low is then likely to become an extratropical low by day 4, and it forecast to begin producing gale-force winds well east of New England to the south of Atlantic Canada.

Although coastal storm surge flooding will gradually subside tonight and Saturday, it cannot be emphasized enough that another serious hazard associated with slow-moving Florence will continue to be extremely heavy rainfall. More than a foot of rain has already fallen across portions of southeastern North Carolina, and more rain is still to come, which will cause disastrous flooding that will spread inland through the weekend.

Key Messages:

1. Life-threatening storm surge will continue along portions of the North Carolina coast through tonight, and also along the Neuse and Pamlico Rivers in western Pamlico Sound, where rainfall and freshwater flooding will also contribute to high water levels. Dangerous storm surge could also affect portions of the northeast coast of South Carolina coast tonight.

2. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into southwest Virginia through early next week, as Florence moves slowly inland. In addition to the flash flood and flooding threat, landslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia.

3. Tropical storm conditions will continue along the coast within the tropical storm warning area and also well inland across portions of South Carolina and North Carolina through Saturday.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 33.8N  79.1W   55 KT  65 MPH - Tropical Storm (Conway, SC)
 12H  15/1200Z 33.7N  79.6W   45 KT  50 MPH - Tropical Storm (Indiantown, SC)
 24H  16/0000Z 33.8N  80.5W   35 KT  40 MPH - Tropical Storm (Wedgewood, SC)
 36H  16/1200Z 34.4N  81.8W   30 KT  35 MPH - Tropical Storm (Joanna, SC)
 48H  17/0000Z 35.9N  83.1W   25 KT  30 MPH - Tropical Storm (West Myers, TN)
 72H  18/0000Z 39.3N  81.8W   20 KT  25 MPH - Tropical Storm (Fillmore, OH)
 96H  19/0000Z 41.0N  74.0W   30 KT  35 MPH - Tropical Storm (Old Tappan, NJ)
120H  20/0000Z 43.5N  61.0W   35 KT  40 MPH - Tropical Storm (ESE Lunenburg, Nova Scotia, Canada)

NWS National Hurricane Center Miami FL 500 PM EDT Fri Sep 14 2018

Florence’s   satellite appearance continues to be quite impressive with well-established outflow and a nearly symmetrical cloud pattern. In radar imagery, however, the inner-core convection has continued to weaken and the echoes are now more stratiform in nature, while outer banding remains rather vigorous, especially south of Cape Lookout and Morehead City, North Carolina. An eye is no longer evident, and the pressure has continued to rise to a now estimated to be 972 mb based on nearby surface observations. Air Force Reserve aircraft data, NOAA Doppler weather radar velocity data from Wilmington, and nearby surface observations indicate that Florence’s intensity has decreased to 60 kt, tropical storm status.

Florence has turned westward and the motion estimate is now 270/03 kt. The new 1200Z global and regional model guidance is in good agreement on Florence moving slowly in a general westward direction for the next 48 hours or so, followed by a northward motion on day 3 as the system moves around the western periphery of a narrow subtropical ridge. On days 4 and 5, the cyclone is forecast to turn northeastward and accelerate ahead of an approaching shortwave trough and frontal system, and emerge off the northeast U.S. coast as an extratropical low. The new official forecast track is very similar to the previous advisory, and is lies near the northern and eastern edge of model guidance envelope, is closer to the TVCA/TVCN consensus models.

Florence is expected to only slowly weaken overnight due to its proximity to the warm Atlantic where convective bands are expected to continue to develop and propagate inland in the eastern and southern portion of the circulation, which will act to bring down some of the stronger winds aloft. It is worth noting that the last reconnaissance pass indicated 700-mb flight-level winds of 77 kt just east of Charleston, South Carolina, so it won’t take much convection to bring down some of those stronger winds to the surface as gusts. More rapid weakening is forecast over the weekend as Florence moves westward across the higher terrain of central and northwestern South Carolina. The official intensity forecast follows the weakening trend of the previous advisory, and is similar to an average of the GFS- and ECMWF-based Decay SHIPS models.

Although coastal storm surge flooding will gradually subside tonight and Saturday, it cannot be emphasized enough that another serious hazard associated with slow-moving Florence will continue to be extremely heavy rainfall. More than 16 inches of rain has already fallen in many areas across southeastern North Carolina, and more rain is still to come, which will cause disastrous flooding that will spread inland through the weekend.

Key Messages:

1. Life-threatening storm surge will continue along portions of the North Carolina coast through tonight, and also along the Neuse and Pamlico Rivers in western Pamlico Sound, where rainfall and freshwater flooding will also contribute to high water levels. Dangerous storm surge could also affect portions of the northeast coast of South Carolina coast tonight.

2. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into southwest Virginia through early next week, as Florence moves slowly inland. In addition to the flash flood and flooding threat, mudslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia.

3. Tropical storm conditions will continue along the coast within the tropical storm warning area and also well inland across portions of South Carolina and North Carolina.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 34.0N  78.6W   60 KT  70 MPH - Tropical Storm (Pireway, NC)
 12H  15/0600Z 33.9N  79.3W   50 KT  60 MPH - Tropical Storm (Brittons Neck, SC)
 24H  15/1800Z 33.9N  80.3W   40 KT  45 MPH - Tropical Storm (Sumter, SC)
 36H  16/0600Z 34.4N  81.4W   25 KT  30 MPH - Tropical Storm (Blair, SC)
 48H  16/1800Z 35.5N  82.6W   25 KT  30 MPH - Tropical Storm (Bent Creek, NC)
 72H  17/1800Z 38.5N  82.6W   20 KT  25 MPH - Tropical Storm (Coal Grove, OH)
 96H  18/1800Z 41.5N  76.0W   20 KT  25 MPH - Tropical Storm (Tunkhannock, PA)
120H  19/1800Z 44.0N  64.5W   30 KT  35 MPH - Tropical Storm (East Berlin, Nova Scotia, Canada)

NWS National Hurricane Center Miami FL 200 PM EDT Fri Sep 14 2018

SUMMARY OF 200 PM EDT...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...34.0N 78.4W
ABOUT 35 MI...55 KM WSW OF WILMINGTON NORTH CAROLINA
ABOUT 35 MI...55 KM ENE OF MYRTLE BEACH SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...968 MB...28.58 INCHES

DISCUSSION AND OUTLOOK

At 200 PM EDT (1800 UTC), the center of Hurricane Florence was located near latitude 34.0 North, longitude 78.4 West. Florence is now moving toward the west near 5 mph (7 km/h). A slow westward to west-southwestward motion is expected today through Saturday. On the forecast track, the center of Florence will move farther inland across extreme southeastern North Carolina today, and across extreme eastern South Carolina tonight and Saturday. Florence will then move generally northward across the western Carolinas and the central Appalachian Mountains early next week.

Maximum sustained winds have decreased to near 75 mph (120 km/h) with higher gusts, mainly over water. Gradual weakening is forecast later today and tonight. Significant weakening is expected over the weekend and into early next week while Florence moves farther inland.

Hurricane-force winds extend outward up to 35 miles (55 km) from the center and tropical-storm-force winds extend outward up to 170 miles (280 km). A wind gust to 66 mph (106 km/h) was recently reported at the National Ocean Service station in Wrightsville Beach, and a 75 mph (121 km/h) was recently reported at a Weatherflow site just north of Cape Fear at Federal Point. Farther inland across North Carolina, a wind gust of 60 mph (96 km/h) was recently at the Fayetteville airport.

The estimated minimum central pressure based on surface observations is 968 mb (28.58 inches).

NWS National Hurricane Center Miami FL 100 PM EDT Fri Sep 14 2018

1:00 PM EDT Fri Sep 14
Location: 34.0°N 78.3°W
Moving: W at 6 mph
Min pressure: 968 mb
Max sustained: 75 mph

NWS National Hurricane Center Miami FL 1200 PM EDT Fri Sep 14 2018

Corrected direction of motion in summary block. …

Tornado Probability
Tornado Probability

FLORENCE WOBBLING SLOWLY WESTWARD OVER EXTREME SOUTHERN NORTH CAROLINA

NOAA Doppler weather radar data and surface observations indicate that the center of Hurricane Florence has turned back toward west. An erratic motion between westward and west-southwestward is likely today.

During the past hour, a station operated by Weatherflow at Federal Point, North Carolina, reported a sustained wind of 56 mph (90 km/h) and a gust to 72 mph (116 km/h), a sustained wind of 53 mph (85 km/h) and a gust to 72 mph (116 km/h) was observed at Mercer Pier in Wrightsville Beach, and a sustained wind of 51 mph (82 km/h) and a gust to 75 mph (121 km/h) was measured at the Wilmington offshore buoy. In addition, an Amateur Radio operator in Oak Island near Cape Fear, North Carolina, recently reported a sustained wind of 68 mph (109 km/h) and a gust to 87 mph (140 km/h).

Hurricane Florence Earliest Arrival Tropical Force Winds 1100 Hours September 14 2018

Some Hurricane Florence heavy rainfall reports received thus far:

  • 18.53 inches Oriental, NC 14.07 inches Surf City, NC
  • 13.81 inches WFO Morehead City, NC
  • 13.07 inches Jacksonville, NC
SUMMARY OF 1200 PM EDT...1600 UTC...INFORMATION
----------------------------------------------
LOCATION...34.0N 78.2W
ABOUT 25 MI...45 KM WSW OF WILMINGTON NORTH CAROLINA
ABOUT 45 MI...75 KM ENE OF MYRTLE BEACH SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...964 MB...28.47 INCHES

NWS National Hurricane Center Miami FL 1100 AM EDT Fri Sep 14 2018

Hurricane Florence’s satellite signature remains very impressive even though the eye is now located just inland over southeastern North Carolina near Cape Fear. However, land interaction has taken its toll on the inner-core circulation, and the previously well-defined eye in radar imagery has shrunk and become filled with rain echoes. The advisory intensity has been lowered to 70 kt based on earlier reports from an Air Force Reserve reconnaissance aircraft, NOAA Doppler weather radar velocity data from Wilmington and Morehead City, and nearby surface observations. The central pressure of 958 mb is based on observations from a NOAA NOS site in Wrightsville Beach and a Weatherflow private station in Federal Point. Another Air Force Hurricane Hunter aircraft will be sampling the portion of Florence’s circulation over water during the next few hours.

Florence has turned west-southwestward and the motion estimate is now 245/03 kt. Florence is expected to remain embedded within a weak steering flow regime within a weakness in the subtropical ridge, resulting in a slow westward motion for the next 36-48 hours across South Carolina. As a shortwave trough currently located over the eastern Great Lakes to Maryland moves eastward away from the region over the next 2 days, the ridge will begin to build back in and shift eastward, allowing Florence or its remnants to gradually turn northward over the weekend, and then move northeastward into the mid-latitude westerlies as an extratropical low. The new NHC forecast track is similar to the previous advisory, and is close to the middle of the model guidance envelope.

Wind data from the earlier aircraft mission, along with Doppler radar velocity data and surface observations, indicate that Florence has weakened. Additional slow weakening is expected today as the center of Florence moves farther inland, with more rapid weakening forecast over the weekend as Florence moves westward across South Carolina. The new NHC intensity forecast is a little lower than the previous advisory, and closely follows the trend of Decay SHIPS model.

Although coastal storm surge flooding will gradually subside later today, it cannot be emphasized enough that another serious hazard associated with slow-moving Florence is and will be extremely heavy rainfall. More than 14 inches of rain has already fallen in many areas across southeastern North Carolina, and more rain is still to come, which will cause disastrous flooding that will spread inland through the weekend.

Key Messages:

1. A life-threatening storm surge is already occurring along portions of the North Carolina coast and will continue through today and tonight. This surge is also likely along portions of the South Carolina coast. The greatest storm surge inundation is expected between Cape Fear and Cape Hatteras, including the Neuse and Pamlico Rivers and western Pamlico Sound.

2. Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians through early next week, as Florence is expected to slow down while it moves inland.

3. Damaging hurricane-force winds are occurring along portions of the North Carolina coast and are expected to spread to portions of the South Carolina coast later today. Strong winds could also spread inland into portions of the Carolinas over the next couple of days.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  14/1500Z 34.0N  78.0W   70 KT  80 MPH - Category 1 (Boiling Spring Lakes, NC)
 12H  15/0000Z 33.9N  78.9W   65 KT  75 MPH - Category 1 (Conway, SC)
 24H  15/1200Z 33.8N  79.7W   55 KT  65 MPH - Tropical Storm (Lake City, SC)
 36H  16/0000Z 33.9N  80.8W   35 KT  40 MPH - Tropical Storm (Congaree, SC)
 48H  16/1200Z 34.7N  82.0W   25 KT  30 MPH - Tropical Storm (Woodruff, SC)
 72H  17/1200Z 37.7N  83.0W   25 KT  30 MPH - Tropical Storm (Ivyton, KY)
 96H  18/1200Z 41.2N  78.4W   20 KT  25 MPH - Tropical Storm (Benezette Township, PA)
120H  19/1200Z 44.4N  68.7W   20 KT  25 MPH - Tropical Storm (Sedgwick, ME)

NWS National Hurricane Center Miami FL 500 AM EDT Fri Sep 14 2018

An Air Force Hurricane Hunter aircraft has been investigating Florence over the past few hours. Data from the aircraft indicate little change in the intensity with the central pressure holding fairly steady. The current intensity estimate is kept at 80 kt for this advisory. There were a couple of SFMR-observed surface winds that were a little higher than that value, however these observations were very near Cape Lookout North Carolina, where shoaling likely caused some inflated wind speeds. The current intensity estimate is also consistent with peak WSR-88D Doppler radar velocities. The center of Florence will be moving inland very soon, but is expected to slow down even more today and tonight. As a result, it will remain fairly close to the coast today, with much of the circulation still over water. Therefore only a gradual decrease in intensity is called for through tonight. Over the weekend, a faster rate of weakening is likely while the center moves at a faster pace and goes farther inland.

The hurricane is turning westward as it continues a slow forward motion of about 285/5 kt. Florence is currently in a region of weak steering currents associated with a col between two mid-level anticyclones. Over the next few days, a high pressure area is forecast to build to the east-northeast of the tropical cyclone. As a result, the system should gradually turn northwestward and northward in 2-3 days. Later in the forecast period, Florence should turn northeastward as it approaches the mid-latitude westerlies. The official track forecast is similar to the previous one and about in the middle of the dynamical guidance suite.

It cannot be emphasized enough that the most serious hazard associated with slow-moving Florence is extremely heavy rainfall, which will cause disastrous flooding that will be spreading inland through the weekend.

Key Messages:

1. A life-threatening storm surge is already occurring along portions of the North Carolina coast and will continue through today and tonight. This surge is also likely along portions of the South Carolina coast. The greatest storm surge inundation is expected between Cape Fear and Cape Hatteras, including the Neuse and Pamlico Rivers and western Pamlico Sound.

2. Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians through early next week, as Florence is expected to slow down while it moves inland.

3. Damaging hurricane-force winds are occurring along portions of the North Carolina coast and are expected to spread to portions of the South Carolina coast later today. Strong winds could also spread inland into portions of the Carolinas over the next couple of days.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

 

ORECAST POSITIONS AND MAX WINDS

INIT  14/0900Z 34.2N  77.4W   80 KT  90 MPH - Category 1 (ENE Wrightsville Beach, NC)
 12H  14/1800Z 34.1N  78.3W   75 KT  85 MPH - Category 1 (Lockwoods Folly, NC)
 24H  15/0600Z 33.9N  79.1W   65 KT  75 MPH - Category 1 (Conway, SC)
 36H  15/1800Z 33.8N  79.9W   45 KT  50 MPH - Tropical Storm ( Union Crossroads, SC)
 48H  16/0600Z 34.1N  81.1W   35 KT  40 MPH - Tropical Storm (Columbia, SC)
 72H  17/0600Z 36.6N  83.2W   25 KT  30 MPH - Tropical Storm (Jonesville, VA)
 96H  18/0600Z 40.5N  80.5W   25 KT  30 MPH - Tropical Storm (Frankfort Springs, PA)
120H  19/0600Z 43.5N  72.0W   25 KT  30 MPH - Tropical Storm (Springfield, NH)

NWS National Hurricane Center Miami FL 1100 PM EDT Thu Sep 13 2018

Radar imagery and data from an Air Force Reserve Hurricane Hunter flight indicate that Florence  has an inner eye that is open on the east side, and a secondary wind maximum that has already begun to spread inland across southeastern North Carolina. The highest flight-level wind (102 kt) was actually measured within the outer band that is moving onshore in the Wilmington area. However, the highest SFMR-measured wind was 73 kt, and the highest land observation so far was a sustained wind of 72 kt at Cape Lookout, North Carolina. On top of that, NOAA Doppler radar velocities have been running around 100 kt at about 5,000 feet. All of these data support reducing the initial intensity to 80 kt, but based on the higher flight-level winds, the gust factor is being set a little higher than is typical for an 80-kt hurricane.

Florence has been wobbling a little since the previous advisory, but the 12-hour motion is northwestward, or 305/5 kt. Nearly all of the track models agree that Florence will turn westward or west-southwestward during the next 36 hours, bringing the hurricane’s center inland over extreme southern North Carolina and extreme eastern South Carolina Friday and Friday night. After 48 hours, Florence is expected to recurve across the western Carolinas and the central Appalachian Mountains around a western Atlantic ridge. No major changes were required to the NHC official track forecast, and it is generally close to the multi-model consensus aids. It should be noted that the ECMWF, HCCA, and Florida State Superensemble still take Florence on a more southern track, straddling the coast of South Carolina before turning inland. While that is not shown by the official forecast, it cannot yet be ruled out as a possibility.

Florence’s intensity is not likely to change much in the 12 hours or so it has left over water. Once the center moves inland, the intensity is forecast to decrease. However, since a good portion of Florence’s circulation will remain over water for the next 36-48 hours, the NHC intensity forecast is a blend of the regular SHIPS model (which assumes a storm staying over water) and the Decay-SHIPS model (which assumes the storm has moved inland). Based on that, Florence should weaken to a tropical storm just after 24 hours and then below tropical storm strength after 48 hours.

Florence remains a large hurricane. Life-threatening storm surge, heavy rainfall, and damaging wind will cover a large area regardless of exactly where the center of Florence moves.

Key Messages:

1. A life-threatening storm surge is already occurring along portions of the North Carolina coast and will continue through Friday. This surge is also likely along portions of the South Carolina coast. The greatest storm surge inundation is expected between Cape Fear and Cape Hatteras, including the Neuse and Pamlico Rivers and western Pamlico Sound.

2. Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians through early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are occurring along portions of the North Carolina coast and are expected to spread to portions of the South Carolina coast on Friday. Strong winds could also spread inland into portions of the Carolinas over the next couple of days.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 34.0N  76.8W   80 KT  90 MPH - Category 1 (E Carolina Beach, NC)
 12H  14/1200Z 34.2N  77.6W   75 KT  85 MPH - Category 1 (E Wrightsville Beach, NC)
 24H  15/0000Z 34.0N  78.5W   65 KT  75 MPH - Category 1 (Shallotte, NC)
 36H  15/1200Z 33.8N  79.2W   50 KT  60 MPH - Category 1 (Hendricks Corner, SC)
 48H  16/0000Z 33.8N  80.2W   40 KT  45 MPH - Tropical Storm (Alcolu, SC)
 72H  17/0000Z 35.5N  82.9W   25 KT  30 MPH - Tropical Storm (Pigeon, NC)
 96H  18/0000Z 39.5N  82.0W   20 KT  25 MPH - Tropical Storm (Wrightstown, OH)
120H  19/0000Z 44.0N  72.5W   25 KT  30 MPH - Tropical Storm ( Chelsea, VT)

NWS National Hurricane Center Miami FL 800 PM EDT Thu Sep 13 2018

DISCUSSION AND OUTLOOK

At 800 PM EDT (0000 UTC), data from NOAA Doppler weather radars and an Air Force Reserve Hurricane Hunter aircraft indicate that the center of the eye of Florence was located near latitude 33.9 North, longitude 76.4 West. Florence is moving slowly toward the northwest near 5 mph (7 km/h), but a slow west-northwestward motion is expected to resume tonight or Friday. A slow westward to west-southwestward motion is expected Friday night and Saturday. On the forecast track, the center of Florence will approach the coasts of North and South Carolina later tonight, then move near or over the coast of southern North Carolina and northeastern South Carolina in the hurricane warning area on Friday. A slow motion across portions of eastern and central South Carolina is forecast Friday night through Saturday night.

Wind data from the Hurricane Hunter aircraft indicate that maximum sustained winds remain near 100 mph (155 km/h) with higher gusts. Little change in strength is expected before the eye of Florence reaches the coast, with slow weakening expected after the center moves inland or meanders near the coast. More significant weakening is forecast on Saturday as Florence moves farther inland over central South Carolina.

Hurricane-force winds extend outward up to 80 miles (130 km) from the center and tropical-storm-force winds extend outward up to 195 miles (315 km). A NOAA observing site at Cape Lookout, North Carolina recently reported a sustained wind of 82 mph (131 km/h) and a gust to 97 mph (156 km/h). A Weatherflow station at Fort Macon, North Carolina, recently reported a sustained wind of 67 mph (108 km/h) and a gust to 99 mph (159 km/h).

Data from the plane indicate that the minimum central pressure remains 955 mb (28.20 inches).

HAZARDS AFFECTING LAND

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground…

Cape Fear NC to Cape Lookout NC…7-11 ft, with locally higher amounts in the Neuse, Pamlico, Pungo, and Bay Rivers

Cape Lookout NC to Ocracoke Inlet NC…6-9 ft

South Santee River SC to Cape Fear NC…4-6 ft

Ocracoke Inlet NC to Salvo NC…4-6 ft Salvo NC to North Carolina/Virginia Border…2-4 ft

Edisto Beach SC to South Santee River SC…2-4 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: Florence is expected to produce heavy and excessive rainfall in the following areas… Southeastern coastal North Carolina into far northeastern South Carolina…20 to 30 inches, isolated 40 inches. This rainfall will produce catastrophic flash flooding and prolonged significant river flooding. Remainder of South Carolina and North Carolina into southwest Virginia…6 to 12 inches, isolated 15 inches. This rainfall will produce life-threatening flash flooding.

WIND: Hurricane conditions have reached portions of the coast of North Carolina and are expected to spread elsewhere within the hurricane warning area overnight or early Friday. Tropical storm conditions are expected to spread inland and south across the remainder of the warning areas through Saturday.

TORNADOES: A few tornadoes are possible in eastern and southeastern North Carolina through Friday.

SURF: Swells generated by Florence are affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

NWS National Hurricane Center Miami FL 700 PM EDT Thu Sep 13 2018

7:00 PM EDT Thu Sep 13 
Location: 33.9°N 76.4°W (ESE Carolina Beach, NC)
Moving: WNW at 5 mph
Min pressure: 955 mb
Max sustained: 100 mph

A NOAA observing site at Cape Lookout, North Carolina, recently reported a sustained wind of 82 mph (131 km/h) and a gust to 97 mph (156 km/h). A private weather station in Davis, North Carolina, recently reported a sustained wind of 59 mph (95 km/h). A Weatherflow station at Fort Macon, North Carolina, recently reported a sustained wind of 61 mph (98 km/h) and a wind gust of 81 mph (130 km/h). Water levels continue to rise quickly on the western side of Pamlico Sound. A gauge at Oriental, North Carolina, on the Neuse River is recording a water height of about 5.5 feet above normal levels.

SUMMARY OF 700 PM EDT…2300 UTC…INFORMATION

LOCATION…33.9N 76.4W ABOUT 85 MI…135 KM ESE OF WILMINGTON NORTH CAROLINA

ABOUT 145 MI…230 KM E OF MYRTLE BEACH SOUTH CAROLINA

MAXIMUM SUSTAINED WINDS…100 MPH…155 KM/H PRESENT MOVEMENT…WNW OR 295 DEGREES AT 5 MPH…8 KM/H

MINIMUM CENTRAL PRESSURE…955 MB…28.20 INCHES

NWS National Hurricane Center Miami FL 600 PM EDT Thu Sep 13 2018

6:00 PM EDT Thu Sep 13 
Location: 33.9°N 76.3°W (ESE Wrightsville Beach, NC(
Moving: WNW at 5 mph
Min pressure: 955 mb
Max sustained: 105 mph

DANGEROUS STORM SURGE FLOODING OCCURRING

ON THE WESTERN SIDE OF PAMLICO SOUND

Hurricane Florence 120 Hour Rainfall 8pm September 13-18

NWS National Hurricane Center Miami FL 200 PM EDT Thu Sep 13 2018

Hurricane Florence

SUMMARY OF 200 PM EDT...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...33.6N 76.0W
ABOUT 110 MI...180 KM ESE OF WILMINGTON NORTH CAROLINA
ABOUT 165 MI...270 KM E OF MYRTLE BEACH SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...955 MB...28.20 INCHES

DISCUSSION AND OUTLOOK

At 200 PM EDT (1800 UTC), data from an Air Force Reserve Unit Hurricane Hunter aircraft and NOAA Doppler weather radars indicate that Florence was located near latitude 33.6 North, longitude 76.0 West. Florence is moving toward the northwest near 10 mph (17 km/h). This general motion, accompanied by a gradual decrease in forward speed, is expected through today. A turn toward the west- northwest and west at an even slower forward speed is expected by tonight and continuing into Friday, and a slow west-southwestward motion is forecast Friday night and Saturday. On the forecast track, the center of Florence will approach the coasts of North and South Carolina later today, then move near or over the coast of southern North Carolina and northeastern South Carolina in the hurricane warning area tonight and Friday. A slow motion across portions of eastern South Carolina is forecast Friday night through Saturday night.

Data from the aircraft and Doppler weather radars indicate that maximum sustained winds remain near 105 mph (165 km/h) with higher gusts. Little change in strength is expected before the eye of Florence reaches the coast, with weakening expected after the center moves inland.

Florence is a large hurricane. Hurricane-force winds extend outward up to 80 miles (130 km) from the center and tropical-storm-force winds extend outward up to 195 miles (315 km). A NOAA reporting station at Cape Lookout, North Carolina, recently reported a sustained wind of 53 mph (85 km/h) and a gust to 63 mph (101 km/h). Weatherflow private observing stations in North Carolina recently reported a sustained wind of 53 mph (85 km/h) and a gust to 70 mph (113 km/h) at Fort Macon, a sustained wind of 47 mph (72 km/h) and a gust to 60 mph (97 km/h) in Ocracoke, and a sustained wind of 45 mph (72 km/h) and a gust to 56 mph (90 km/h) in Pamlico Sound.

The estimated minimum central pressure based on recent data from the aircraft remains at 955 mb (28.20 inches).

HAZARDS AFFECTING LAND

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground if peak surge occurs at the time of high tide…

Cape Fear NC to Cape Lookout NC, including the Neuse, Pamlico, Pungo, and Bay Rivers…9-13 ft

North Myrtle Beach SC to Cape Fear NC…6-9 ft

Cape Lookout NC to Ocracoke Inlet NC…6-9 ft South Santee River SC to North Myrtle Beach SC…4-6 ft

Ocracoke Inlet NC to Salvo NC…4-6 ft

Salvo NC to North Carolina/Virginia Border…2-4 ft

Edisto Beach SC to South Santee River SC…2-4 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: Florence is expected to produce heavy and excessive rainfall in the following areas… Coastal North Carolina into far northeastern South Carolina…20 to 30 inches, isolated 40 inches. This rainfall will produce catastrophic flash flooding and prolonged significant river flooding. Remainder of South Carolina and North Carolina into southwest Virginia…6 to 12 inches, isolated 15 inches.

WIND: Hurricane conditions are expected to reach the coast within the hurricane warning area this evening or early Friday. Tropical storm conditions are already moving onshore within the warning area.

TORNADOES: A few tornadoes are possible in eastern North Carolina through Friday.

SURF: Swells generated by Florence are affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

NWS National Hurricane Center Miami FL 1100 AM EDT Thu Sep 13 2018

The satellite and radar presentations of Hurricane Florence have improved somewhat this morning, with a 20-25 nmi wide eye closing off in the radar data from the Morehead City and Wilmington WSR-88D Doppler weather radars. However, an Air Force Reserve reconnaissance aircraft investigating the hurricane this morning has not yet found any flight-level or SFMR winds to support more than about 80 kt at the surface thus far, even though the pressure has decreased to 955 mb. The initial intensity has only been lowered to 90 kt, given that there are peak Doppler velocity values up to 110 kt with average values of 95-97 kt at 15,000 ft in the northern eyewall region, an area of the hurricane that the reconnaissance aircraft has not yet sampled. The upper-level outflow pattern remains quite impressive.

Florence has been gradually slowing down this morning, and the initial motion estimate is now 315/09 kt. The subtropical ridge to the northeast and east of Florence is now well-established between Bermuda and the U.S. mid-Atlantic region and extends westward into Virginia and the central Appalachians. This large-scale feature is expected to keep the hurricane moving northwestward today, followed by a turn toward the west at a much slower speed on Friday as the ridge to the north of Florence weakens due to a weak shortwave trough dropping slowly southward from the Ohio Valley. On days 3-5, Florence is forecast turn toward the northwest and north around the western periphery of the subtropical ridge, and move across western South Carolina on Sunday, across western North Carolina and eastern Tennessee on Monday, and then move up the spine of the Appalachians as an extratropical low after the cyclone merges or interacts with a frontal system. The new NHC forecast track is similar to the previous one, and lies close to a blend of the consensus models TVCA, HCCA, and FSSE.

Florence is currently approaching the Gulfstream current, and the hurricane is forecast to move over warmer and deeper waters in 6-12 hours, which could allow for some slight strengthening. Just prior to landfall in about 24 hours, Florence is expected to weaken some due to upwelling of the shallow coastal waters. After landfall occurs, rapid weaning of the stronger inner-core wind field is expected to due land interaction and Florence’s slow forward speed of 5 kt or less. However, intense rainbands are expected to develop over the Atlantic waters and keep moving along the coast and inland, likely producing strong wind gusts through Saturday night.

Aircraft and satellite wind data show that Florence remains a large hurricane. Life-threatening storm surge, heavy rainfall, and damaging wind will cover a large area regardless of exactly where the center of Florence moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. The greatest storm surge inundation is expected between Cape Fear and Cape Hatteras, including the Neuse and Pamlico Rivers and western Pamlico Sound.

2. Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians through early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina as soon as this evening, and a Hurricane Warning is in effect. Strong winds could also spread inland into portions of the Carolinas.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 33.4N  75.5W   90 KT 105 MPH - Category 2 (ENE Myrtle Beach, SC)
 12H  14/0000Z 33.9N  76.6W   95 KT 110 MPH - Category 2 (SW Kure Beach, NC)
 24H  14/1200Z 34.2N  77.8W   85 KT 100 MPH - 1 Category 1 (Wrightsville Beach, NC)
 36H  15/0000Z 34.1N  78.7W   65 KT  75 MPH - 1 Category 1 (Nakina, NC)
 48H  15/1200Z 34.0N  79.6W   45 KT  50 MPH - Tropical Storm (Pamplico, SC)
 72H  16/1200Z 34.3N  81.8W   25 KT  30 MPH - Tropical Storm (Silverstreet, SC)
 96H  17/1200Z 36.9N  83.0W   25 KT  30 MPH - Tropical Storm (Holmes Mill, KY)
120H  18/1200Z 40.3N  79.2W   20 KT  25 MPH - Tropical Storm (Wilpen, PA)

NWS National Hurricane Center Miami FL 900 AM EDT Thu Sep 13 2018

…HEAVY RAINBANDS WITH TROPICAL-STORM-FORCE WINDS SPREADING OVER THE NORTH CAROLINA OUTER BANKS… …LIFE-THREATENING STORM SURGE AND RAINFALL EXPECTED…

Data from an Air Force Reserve Unit Hurricane Hunter aircraft and NOAA Doppler weather radars from Morehead City and Wilmington, North Carolina, indicate that Florence has changed little. Maximum sustained winds remain near 110 mph (175 km/h). The latest minimum central pressure based on data from the aircraft is 957 mb (28.26 inches).

SUMMARY OF 900 AM EDT…1300 UTC…

INFORMATION

LOCATION…33.2N 75.2W

ABOUT 170 MI…275 KM ESE OF WILMINGTON NORTH CAROLINAHurricane Florence Surface Wind Field 0800 Hours September 13 2018

ABOUT 215 MI…345 KM E OF MYRTLE BEACH SOUTH CAROLINA

MAXIMUM SUSTAINED WINDS…110 MPH…175 KM/H PRESENT MOVEMENT…NW OR 315 DEGREES AT 12 MPH…20 KM/H

MINIMUM CENTRAL PRESSURE…957 MB…28.26 INCHES

NWS National Hurricane Center Miami FL 500 AM EDT Thu Sep 13 2018

The satellite presentation of Florence has changed little overnight with the eye waxing and waning in infrared imagery. The eye has moved into NWS radar range and can be seen in radar data from Morehead City and Wilmington NWS 88-D imagery. An 0616 UTC AMSR2 microwave overpass indicated that the convection over the southern and southeastern portions of the storm is still disrupted, and that the eyewall was open to the southeast. An Air Force Hurricane Hunter aircraft also reported that the eyewall was not fully intact on its last pass through the storm just after that time. The Air Force plane measured a peak 700-mb flight level wind of 102 kt and peak SFMR winds of 85 kt during the mission. These data suggest that the intensity may be slightly lower, but the initial intensity has been maintained at 95 kt, since the plane may not have sampled the strongest winds. Another Air Force plane will be in Florence shortly, and should provide a better assessment of the intensity of the hurricane. As mentioned in the previous discussion, it appears that some southern shear has caused the degradation of the inner core. The global models suggest that this shear will relax today while Florence moves over warm waters, however, given the current storm structure, little overall change in strength is anticipated as Florence approaches the coast. Gradual weakening should occur as the hurricane interacts with land in 24-36 h, with a faster rate of weakening predicted once Florence moves farther inland.Hurricane Florence Tropical Force Winds 0500 Hours September 13 2018

Florence is moving northwestward or 315 degrees at 13 kt. A developing mid-level ridge over the north-central United States should cause the forward speed of the hurricane to decrease today. As the steering currents collapse tonight and Friday, Florence is forecast to drift westward or west-southwestward and continue that slow motion into the weekend. The global models predict that the ridge will slide eastward over the weekend, which should allow Florence to turn northwestward and northward by the end of the forecast period. Although there is still some spread in the guidance by 48 hours, with the GFS along the northern side of the guidance envelope, and the ECWMF along the southern edge, the various consensus aids have moved little. As a result, the new NHC forecast track is very similar to the previous advisory.

Aircraft and satellite wind data show that Florence is a large hurricane. Life-threatening storm surge, heavy rainfall, and damaging wind will cover a large area regardless of exactly where the center of Florence moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. All interests in these areas should complete preparations and follow any advice given by local officials.

2. Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Warning is in effect. Strong winds could also spread inland into portions of the Carolinas.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  13/0900Z 32.8N  74.7W   95 KT 110 MPH - Category 2 (E Charleston, SC)
 12H  13/1800Z 33.7N  76.1W   95 KT 110 MPH - Category 2 (E Bald Head Island, NC)
 24H  14/0600Z 34.2N  77.4W   90 KT 105 MPH - Category 1 (E Wrightsville Beach, NC)
 36H  14/1800Z 34.3N  78.4W   70 KT  80 MPH - Category 1 ( Bolton, NC)
 48H  15/0600Z 34.1N  79.2W   50 KT  60 MPH - Tropical Storm (Ketchuptown,, SC)
 72H  16/0600Z 33.9N  81.2W   30 KT  35 MPH - Tropical Storm (Red Bank, SC)
 96H  17/0600Z 35.4N  83.3W   25 KT  30 MPH - Tropical Storm (Wilmot, NC)
120H  18/0600Z 39.5N  81.0W   20 KT  25 MPH - Tropical Storm (Adonis, WV)

NWS National Hurricane Center Miami FL 1100 PM EDT Wed Sep 12 2018

Satellite data and reports from Hurricane Hunter aircraft indicate significant changes in the structure of Florence and the environment near the storm since the last advisory. Microwave satellite imagery shows that the convection on the southern side of the storm has been disrupted, and reports from an Air Force Reserve Hurricane Hunter aircraft indicate the eyewall now wraps less than 50 percent of the way around the center. The aircraft also reports that the hurricane again has concentric wind maxima, the inner at a radius 20-30 n mi and the outer at 50-60 n mi. The convection seems to have been affected by 20-25 kt of southerly vertical wind shear, most of which appears to be due to strong winds between 200-250 mb seen in dropsonde data from the NOAA G-IV jet. The central pressure has risen to 957 mb, and the maximum 700-mb flight-level winds reported so far are 103 kt. Based on the latter data, the initial intensity reduced to a probably generous 95 kt.

The initial motion is 315/15. During the next 12-36 hours, the hurricane is expected to turn toward the west-northwest and west with a decrease in forward speed as it moves into an area of weakening steering currents near and over the southeastern United States. The new forecast track now brings the center onshore in southern North Carolina near the 36 h point. After landfall, the cyclone should move slowly westward to west-southwestward through the 72 h point, then it should turn northwestward to northward by the end of the forecast period as it moves through the Appalachian Mountains. The new forecast track lies between the HCCA corrected consensus model and the other consensus aids, and it is nudged just a little to the north of the previous track.

The dynamical models forecast the current shear to subside after 6-12 h as Florence moves farther from an upper-level low currently near northeastern Florida. This, combined with sea surface temperatures near 29C, would allow a last chance for strengthening before landfall. However, the storm structure, particularly the large outer wind maxima, would likely be slow to respond to the more favorable environment. The pre-landfall part of the intensity forecast thus calls for little change in strength, but given the uncertainties the confidence in this is low. After landfall, Florence should gradually weaken during the 36-48 h period while the center is near the coast, then weaken more quickly when the center moves farther inland. While Florence has weakened below major hurricane intensity, the wind field of the hurricane continues to grow in size. This evolution will produce storm surges similar to that of a more intense, but smaller, hurricane, and thus the storm surge values seen in the previous advisory are still valid. The threat of rainfall has also not diminished, and these impacts will cover a large area regardless of exactly where the center of Florence moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. All interests in these areas should complete preparations and follow any advice given by local officials.

2. Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Warning is in effect. Strong winds could also spread inland into portions of the Carolinas.

4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  13/0300Z 32.0N  73.7W   95 KT 110 MPH - Category 2 (S Charleston, SC)
 12H  13/1200Z 33.1N  75.3W   95 KT 110 MPH - Category 2 (ESE Myrtle Beach, SC)
 24H  14/0000Z 33.9N  76.7W   95 KT 110 MPH - Category 2 (Bald Head Island, NC)
 36H  14/1200Z 34.2N  78.0W   80 KT  90 MPH - Category 1 (Leland, NC)
 48H  15/0000Z 34.1N  78.7W   60 KT  70 MPH - Tropical Storm (Nakina, NC)
 72H  16/0000Z 33.5N  80.5W   40 KT  45 MPH - Tropical Storm (Santee, SC)
 96H  17/0000Z 34.0N  83.0W   25 KT  30 MPH - Tropical Storm (Carlton, GA)
120H  18/0000Z 37.5N  83.5W   20 KT  25 MPH - Tropical Storm (Guerrant, KY)

NWS National Hurricane Center Miami FL 800 PM EDT Wed Sep 12 2018

DISCUSSION AND OUTLOOK

At 800 PM EDT (0000 UTC), the center of Hurricane Florence was located near latitude 31.5 North, longitude 73.2 West. Florence is moving toward the northwest near 16 mph (26 km/h), and this general motion, accompanied by a gradual decrease in forward speed, is expected to continue through Saturday. On the forecast track, the center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas tonight, and approach the coast of North Carolina or South Carolina in the hurricane warning area on Thursday and Friday, and move slowly near the coastline through Saturday.

Reports from an Air Force Reserve Hurricane Hunter aircraft indicate that maximum sustained winds have decreased to near 115 mph (185 km/h) with higher gusts. Florence is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some fluctuations in strength are possible through Thursday morning. Although slow weakening is expected to begin by late Thursday, Florence is forecast to be an extremely dangerous major hurricane when it nears the U.S. coast late Thursday and Friday.

Hurricane-force winds extend outward up to 70 miles (110 km) from the center and tropical-storm-force winds now extend outward up to 195 miles (315 km).

The minimum central pressure extrapolated by the Hurricane Hunter aircraft is 956 mb (28.23 inches).

HAZARDS AFFECTING LAND

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground if peak surge occurs at the time of high tide…

Cape Fear NC to Cape Lookout NC, including the Neuse, Pamlico, Pungo, and Bay Rivers…9-13 ft

North Myrtle Beach SC to Cape Fear NC…6-9 ft Cape Lookout NC to Ocracoke Inlet NC…6-9 ft South Santee River SC to North Myrtle Beach SC…4-6 ft

Ocracoke Inlet NC to Salvo NC…4-6 ft

Salvo NC to North Carolina/Virginia Border…2-4 ft Edisto Beach SC to South Santee River SC…2-4 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: Florence is expected to produce heavy and excessive rainfall in the following areas… Coastal North Carolina…20 to 30 inches, isolated 40 inches. This rainfall would produce catastrophic flash flooding and significant river flooding. South Carolina, western and northern North Carolina…5 to 10 inches, isolated 20 inches. Elsewhere in the Appalachians and Mid-Atlantic states…3 to 6 inches, isolated 12 inches.

WIND: Hurricane conditions are expected to reach the coast within the hurricane warning area late Thursday or Friday. Winds are expected to first reach tropical storm strength on Thursday, making outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

TORNADOES: A few tornadoes are possible in eastern North Carolina beginning late Thursday morning.

SURF: Swells generated by Florence are affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

 

NWS National Hurricane Center Miami FL 500 PM EDT Wed Sep 12 2018

Data from an Air Force Reserve hurricane hunter aircraft along with satellite imagery and various intensity estimates indicate that Florence has weakened instead of strengthening. However, while the hurricane hasn’t strengthened in terms of peak winds, the inner-core and outer wind fields have continued to expand, resulting in an increase the cyclone’s total energy, which will create a significant storm surge event. The upper-level outflow remains impressive and is still expanding except toward the south.

Florence is moving toward the northwest or 315/14 kt. The new 12Z global and regional model runs have come into much better agreement on Florence moving steadily northwestward around a strong ridge located between Bermuda and the U.S. mid-Atlantic region for the next 48 hours or so. By late on day 2, Florence is forecast to approach the southern portion of the North Carolina coast, then slow down considerably and turn westward within collapsing steering flow, with a very slow westward motion near the coasts of North and South Carolina continuing into Friday and Saturday. Corrected-consensus models HCCA and FSSE remain very close to each other and are quite similar to the simple consensus model TVCA. Therefore, only a slight eastward shift was needed to the previous forecast track through 36 hours or so, mainly due to the more eastward initial position based on the reconnaissance fixes. At 48 hours and beyond, no significant changes were required to the previous advisory track, which still shows Florence moving slowly westward across South Carolina and western North Carolina on day 4, followed by a slow northward motion up the Appalachian mountain chain on day 5.

A narrow window of opportunity remains during the next 24 hours or so for Florence to strengthen a little when the hurricane passes over the warmer SSTs and deeper warm water/higher upper-ocean heat content associated with the Gulf Stream, and low vertical shear conditions of 5-10 kt will aid in any strengthening process. However, significant strengthening is not anticipated due to Florence’s large and expanding inner-core wind field. By 36 h and beyond, decreasing ocean heat content along with the slowing forward speed of Florence will likely produce cold upwelling beneath the hurricane, inducing a gradual weakening trend. When Florence moves over the shallow coastal shelf waters in 48-72 h, land interaction and more significant upwelling are anticipated, which should further enhance the weakening process. The NHC intensity forecast remains near the higher statistical guidance through 48 hours, then follows the trend of the decay SHIPS model after that time.

Although the maximum winds are expected to weaken a little more, Florence is still expected to remain a dangerous major hurricane as it approaches the coast. The threat to life from storm surge and rainfall will not diminish, and these impacts will cover a large area regardless of exactly where the center of Florence moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. All interests in these areas should complete preparations and follow any advice given by local officials.

2. Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Warning is in effect. Strong winds could also spread inland into portions of the Carolinas. 4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 30.9N  72.5W  105 KT 120 MPH - Category 3 (NE Jacksonville, FL)
 12H  13/0600Z 32.1N  74.1W  110 KT 125 MPH - Category 3 (SE Charleston, SC)
 24H  13/1800Z 33.4N  75.9W  110 KT 125 MPH - Category 3 (North Myrtle Beach, SC)
 36H  14/0600Z 33.9N  77.1W  105 KT 120 MPH - Category 3 (NE Kure Beach,NC)
 48H  14/1800Z 34.0N  77.9W  100 KT 115 MPH - Category 3 (Kure Beach,NC)
 72H  15/1800Z 33.6N  79.2W   70 KT  80 MPH - Category 1 (Yauhannah, SC)
 96H  16/1800Z 34.0N  81.7W   30 KT  35 MPH - Tropical Storm ( Emory, SC)
120H  17/1800Z 35.6N  83.4W   20 KT  25 MPH - Tropical Storm (Cherokee, NC)

NWS National Hurricane Center Miami FL 500 PM EDT Wed Sep 12 2018

DISCUSSION AND OUTLOOK

At 500 PM EDT (2100 UTC), the center of Hurricane Florence was located near latitude 30.9 North, longitude 72.5 West. Florence is moving toward the northwest near 16 mph (26 km/h), and this general motion, accompanied by a gradual decrease in forward speed, is expected to continue through Saturday. On the forecast track, the center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas tonight, and approach the coast of North Carolina or South Carolina in the hurricane warning area on Thursday and Friday, and move slowly near the coastline through Saturday.

Maximum sustained winds have decreased to near 120 mph (195 km/h) with higher gusts. Florence is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some fluctuations in strength will be possible through Thursday morning. Although slow weakening is expected to begin by late Thursday, Florence is forecast to be an extremely dangerous major hurricane when it nears the U.S. coast late Thursday and Friday.Hurricane Florence Arrival Tropical Force Winds 1100 Hours September 12 2018

Hurricane-force winds extend outward up to 70 miles (110 km) from the center and tropical-storm-force winds now extend outward up to 195 miles (315 km).

The estimated minimum central pressure is 949 mb (28.03 inches).

NWS National Hurricane Center Miami FL 200 PM EDT Wed Sep 12 2018

DISCUSSION AND OUTLOOK

At 200 PM EDT (1800 UTC), reports from An Air Force Reserve reconnaissance aircraft indicate that the center of the eye of Hurricane Florence was located near latitude 30.4 North, longitude 71.8 West. Florence is moving toward the northwest near 16 mph (26 km/h) and this general motion, accompanied by a gradual decrease in forward speed, is expected to through Saturday. On the forecast track, the center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas today, and approach the coast of North Carolina or South Carolina in the hurricane warning area on Thursday and Friday and move slowly near the coastline through Saturday.

The reconnaissance aircraft found that maximum sustained winds have decreased to near 125 mph (205 km/h) with higher gusts. Florence is now a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some fluctuations in strength will be possible through Thursday morning. Although slow weakening is expected to begin by late Thursday, Florence is still forecast to be an extremely dangerous major hurricane when it nears the U.S. coast late Thursday and Friday.

Hurricane-force winds extend outward up to 70 miles (110 km) from the center and tropical-storm-force winds extend outward up to 175 miles (280 km). A NOAA buoy located about 100 miles northeast of Florence’s eye recently reported a sustained wind of 53 mph (85 km/h) and a gust to 74 mph (119 km/h).

The minimum central pressure based on reports from the reconnaissance aircraft is estimated to be 948 mb (27.99 inches).

HAZARDS AFFECTING LAND

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground if peak surge occurs at the time of high tide…

Cape Fear NC to Cape Lookout NC, including the Neuse, Pamlico, Pungo, and Bay Rivers…9-13 ft

North Myrtle Beach SC to Cape Fear NC…6-9 ft

Cape Lookout NC to Ocracoke Inlet NC…6-9 ft

South Santee River SC to North Myrtle Beach SC…4-6 ft

Ocracoke Inlet NC to Salvo NC…4-6 ft Salvo NC to North Carolina/Virginia Border…2-4 ft

Edisto Beach SC to South Santee River SC…2-4 ft

RAINFALL: Florence is expected to produce heavy and excessive rainfall in the following areas… Coastal North Carolina…20 to 30 inches, isolated 40 inches. This rainfall would produce catastrophic flash flooding and significant river flooding. South Carolina, western and northern North Carolina…5 to 10 inches, isolated 20 inches. Elsewhere in the Appalachians and Mid-Atlantic states…3 to 6 inches, isolated 12 inches.

WIND: Hurricane conditions are expected to reach the coast within the hurricane warning area late Thursday or Friday. Winds are expected to first reach tropical storm strength on Thursday, making outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

TORNADOES: A few tornadoes are possible in eastern North Carolina beginning late Thursday morning.

SURF: Swells generated by Florence are affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

NWS National Hurricane Center Miami FL 1100 AM EDT Wed Sep 12 2018

An Air Force Reserve hurricane hunter aircraft investigating Florence this morning has found no change in the hurricane’s peak intensity of 115 kt, even though the central pressure had decreased a few millibars down to 943 mb. However, the aircraft data do indicate that Florence’s inner-core wind field has expanded, with the 50-kt wind radii now extending outward up to 100 n mi to the northeast. Florence still has a very distinct eye in satellite imagery, but cloud top temperatures have been waxing and waning in the eyewall region, with slight downward trend noted in the past hour or so. In contrast, the upper-level outflow remains impressive and continues to expand everywhere except to the south.

Florence is now moving toward the northwest or 305/13 kt. There has been no significant change to the NHC model guidance, including the corrected-consensus models HCCA and FSSE, which are now virtually on top of each other and the simple consensus model TVCA. As a result, no changes were required to the previous NHC track. The shortwave trough over the southern Plains seen in water vapor imagery could end up being a significant factor as it rounds the narrow ridge over the Tennessee Valley and is expected to erode the ridge along the U.S. mid-Atlantic coast on days 3-5. At this time, little change has been made to the NHC track forecast, which remains very close to the aforementioned consensus aids through 72 hours. On the current forecast track, the center of Florence is expected to be near the coasts of southern North Carolina and northern South Carolina in 48 to 72 hours and then drift westward to west- southwestward in weak steering flow.

There is still a narrow window of opportunity for Florence to strengthen a little when the cyclone moves over the warmest SSTs and highest upper-ocean heat content while the shear will be the lowest between 0600-1200 UTC tomorrow morning. After that, decreasing ocean heat content along with the slowing forward speed of Florence should cause at least some cold upwelling beneath the hurricane, which should induce a gradual weakening trend. Once Florence reaches the shallow coastal shelf waters in 72 h, land interaction and more significant upwelling are expected, further enhancing the weakening process. The NHC intensity forecast remains near the higher statistical guidance through 48 hours, then follows the trend of the decay SHIPS model after that time.

While Florence’s maximum winds are expected to weaken a little, it is still expected to remain a dangerous major hurricane as it approaches the coast. The threat to life from storm surge and rainfall will not diminish, and these impacts will cover a large area regardless of exactly where the center of Florence moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. All interests in these areas should complete preparations and follow any advice given by local officials.

2. Life-threatening, catastrophic flash flooding and significant river flooding is likely over portions of the Carolinas late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Warning is in effect. Strong winds could also spread inland into portions of the Carolinas.

4. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 29.8N  71.3W  115 KT 130 MPH - Category 4 (E Daytona Beach, FL)
 12H  13/0000Z 31.1N  73.1W  120 KT 140 MPH - Category 4 (ESE Tybee Island, GA)
 24H  13/1200Z 32.6N  75.1W  125 KT 145 MPH - Category 4 (ESE Charleston, SC)
 36H  14/0000Z 33.5N  76.5W  120 KT 140 MPH - Category 4 (ESE Myrtle Beach, SC)
 48H  14/1200Z 33.8N  77.4W  105 KT 120 MPH - Category 3 (ESE Bald Head Island, NC) 
 72H  15/1200Z 33.6N  78.4W   85 KT 100 MPH - Category 2 (ESE Myrtle Beach, SC)
 96H  16/1200Z 33.6N  80.4W   45 KT  50 MPH - Tropical Storm (St Paul, SC)
120H  17/1200Z 34.7N  82.8W   25 KT  30 MPH - Tropical Storm (Clemson, SC)

NWS National Hurricane Center Miami FL 500 AM EDT Wed Sep 12 2018

The eye of Florence remains very distinct in infrared satellite imagery this morning. There has been little change to the cloud top temperatures surrounding the eye overnight, however, the overall cloud shield and central dense overcast has become slightly more symmetric. An Air Force Reserve Hurricane Hunter aircraft that was in the hurricane until just after midnight measured a peak 700-mb flight-level wind of 130 kt, and a SFMR wind of 107 kt in the northeast eyewall. A blend of these data and recent subjective and objective satellite intensity estimates supports an initial wind speed of 115 kt. Florence will be moving over sea surface temperatures of around 29C and through an area of low vertical wind shear during the next day or so. These conditions favor some strengthening, but eyewall replacement cycles could cause some fluctuations in intensity during that time. After that time, an increase in southwesterly shear, upwelling, and interaction with land is likely to lead to some weakening, however, Florence is expected to remain a dangerous major hurricane as it approaches the coastline. The new NHC intensity forecast is near the higher statistical guidance through 48 hours, then follows the trend of the decay SHIPS model after that time.

Florence is moving west-northwestward or 300 degrees at 15 kt. There has been no change to the track forecast or reasoning for the first 36-48 hours, as Florence will continue to be steered west-northwestward to northwestward around the southwestern portion of a mid-level ridge centered northeast of Bermuda. By late Thursday, a mid-level ridge is forecast to begin building over the east-central United States, which is expected to cause Florence to slow down significantly by 48 hours. The track guidance is in good agreement through the first couple of days of the forecast period, and the NHC track forecast again brings the center of the hurricane very close to the coasts of North and South Carolina within 48 hours. Later in the period, the dynamical model spread increases but most of the guidance has continued its southward shift, and now take Florence southwestward near the coast of South Carolina by day 4. The NHC track has been adjusted southward at days 4 and 5, and is a little north of the consensus out of respect for continuity, however, the GFS, ECMWF, and the ECMWF ensemble mean is south of the NHC track forecast, and additional southward adjustment may be warranted in future advisories.

Video: LIVE WATCH LIVE: FEMA officials provide updates on Hurricane Florence

It is important for users to realize that significant impacts extend well away from the center of Florence, and serious hazards such as a dangerous storm surge and flooding rains will cover a large area regardless of exactly where the center moves.

Key Messages:Hurricane Florence Tropical Force Winds 0200 Hours September 12 2018

1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. All interests from South Carolina into the mid-Atlantic region should complete preparations and follow any advice given by local officials.

2. Life-threatening, catastrophic flash flooding and significant river flooding is likely over portions of the Carolinas and Mid-Atlantic states from late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Warning is in effect. Strong winds could also spread inland into portions of the Carolinas.

4. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0900Z 29.0N  70.1W  115 KT 130 MPH - Category 4 (E Daytona Beach, FL)
 12H  12/1800Z 30.3N  72.1W  120 KT 140 MPH - Category 4 (E Jacksonville, FL)
 24H  13/0600Z 32.0N  74.4W  125 KT 145 MPH - Category 4 (ESE Charleston, SC)
 36H  13/1800Z 33.2N  76.1W  120 KT 140 MPH - Category 4 (ESE Myrtle Beach, SC)
 48H  14/0600Z 33.8N  77.3W  105 KT 120 MPH - Category 3 (E Bald Head Island, NC)
 72H  15/0600Z 33.8N  78.2W   85 KT 100 MPH - Category 2 (Oak Island, NC)
 96H  16/0600Z 33.6N  79.7W   45 KT  50 MPH - Tropical Storm (Kingstree, SC)
120H  17/0600Z 34.2N  82.7W   25 KT  30 MPH - Tropical Storm (Lowndesville, SC)

NWS National Hurricane Center Miami FL 1100 PM AST Tue Sep 11 2018Florence’s eye became a little ragged in appearance on satellite images a couple of hours ago, but recently it has become better defined. There has also been a little cooling of the tops surrounding the eye. These features suggest that Florence is maintaining its intensity. The current intensity is kept at 120 kt, which is a little above the adjusted flight-level winds from the Air Force Hurricane Hunters and a little below the latest SATCON estimate from UW-CIMSS. Over the next couple of days, the hurricane is expected to move over a warm ocean and through an environment of low vertical shear. This would allow some additional strengthening until about 48 hours. From that time and up to landfall, the global models suggest some increase in shear which would cause some weakening. However, Florence is still likely to remain a dangerous major hurricane when its center crosses the coast. The official intensity forecast is a blend of the Decay-SHIPS and ICON intensity model consensus.

The initial motion estimate is west-northwestward, or 300/15 kt. A mid-level ridge to the northeast should continue to steer Florence on a west-northwestward to northwestward heading until the hurricane nears the coast. The steering pattern from 72 hours and beyond becomes more complicated and uncertain. The latest GFS model run shows a mid-level ridge building over the east-central United States in 3-4 days. This temporarily blocks the forward progress of the hurricane and forces a southwesterly turn in the model run. Later in the period, the ridge rebuilds to the north of Florence allowing the system to move inland. The official track forecast is somewhat to the left of the previous NHC track, but to the right of the latest consensus predictions. It should be noted that, due to increased model spread, there is substantial uncertainty in the 3-5 track forecast.

It is important for users to realize that significant impacts extend well away from the center of Florence, and serious hazards such as a dangerous storm surge and flooding rains will cover a large area regardless of exactly where the center moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. All interests from South Carolina into the mid-Atlantic region should complete preparations and follow any advice given by local officials.

Hurricane Florence Tropical Force Winds 2000 Hours September 11 2018

2. Life-threatening, catastrophic flash flooding and significant river flooding is likely over portions of the Carolinas and Mid-Atlantic states from late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Warning has been issued for a part of this area. Damaging winds could also spread well inland into portions of the Carolinas and Virginia.

4. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0300Z 28.4N  68.7W  120 KT 140 MPH - Category 4 (ESE Coopers Town, Bahamas)
 12H  12/1200Z 29.6N  70.8W  125 KT 145 MPH - Category 4 (ESE Jacksonville, FL)
 24H  13/0000Z 31.4N  73.4W  135 KT 155 MPH - Category 4 (ESE Hilton Head Island, SC)
 36H  13/1200Z 32.9N  75.5W  130 KT 150 MPH - Category 4 (ESE Georgetown, SC)
 48H  14/0000Z 33.8N  76.8W  115 KT 130 MPH - Category 4 (ESE Carolina Beach, NC)
 72H  15/0000Z 34.3N  78.2W   95 KT 110 MPH - Category 2 (Northwest, NC)
 96H  16/0000Z 34.3N  79.7W   45 KT  50 MPH - Tropical Storm (Florence, SC)
120H  17/0000Z 34.9N  82.5W   25 KT  30 MPH - Tropical Storm (Berea, SC)

NWS National Hurricane Center Miami FL 800 PM AST Tue Sep 11 2018

…DANGEROUS FLORENCE HEADED FOR THE U.S. EAST COAST…
…EXPECTED TO BRING LIFE-THREATENING STORM SURGE AND RAINFALL TO
PORTIONS OF THE CAROLINAS AND MID-ATLANTIC STATES…

SUMMARY OF 800 PM AST…0000 UTC…INFORMATION
———————————————-
LOCATION…28.0N 67.9W
ABOUT 350 MI…565 KM SSW OF BERMUDA
ABOUT 725 MI…1165 KM ESE OF CAPE FEAR NORTH CAROLINA
MAXIMUM SUSTAINED WINDS…140 MPH…220 KM/H
PRESENT MOVEMENT…WNW OR 300 DEGREES AT 17 MPH…28 KM/H
MINIMUM CENTRAL PRESSURE…945 MB…27.91 INCHES

WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for…
* South Santee River South Carolina to Duck North Carolina
* Albemarle and Pamlico Sounds, including the Neuse and Pamlico
Rivers

A Storm Surge Watch is in effect for…
* Edisto Beach South Carolina to South Santee River South Carolina
* North of Duck North Carolina to the North Carolina/Virginia border

A Hurricane Warning is in effect for…
* South Santee River South Carolina to Duck North Carolina
* Albemarle and Pamlico Sounds

A Hurricane Watch is in effect for…
* Edisto Beach South Carolina to South Santee River South Carolina
* North of Duck North Carolina to the North Carolina/Virginia border

A Tropical Storm Watch is in effect for…
* North of the North Carolina/Virginia border to Cape Charles Light
Virginia
* Chesapeake Bay south of New Point Comfort

Interests elsewhere in the southeastern and mid-Atlantic states should monitor the progress of Florence. Additional watches and warnings may be required tonight or Wednesday.

A Storm Surge Warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline, during the next 36 hours in the indicated locations. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at
hurricanes.gov. This is a life-threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.

A Storm Surge Watch means there is a possibility of life- threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm- force winds, conditions that make outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.

DISCUSSION AND OUTLOOK
———————-
At 800 PM AST (0000 UTC), the eye of Hurricane Florence was located by satellite near latitude 28.0 North, longitude 67.9 West. Florence is moving toward the west-northwest near 17 mph (28 km/h). A motion toward the west-northwest and northwest is expected through early Thursday. Florence is expected to slow down considerably by late Thursday into Friday. On the forecast track, the center of Florence will move over the southwestern Atlantic Ocean between
Bermuda and the Bahamas through Wednesday, and approach the coast of North Carolina or South Carolina in the hurricane warning area on Thursday and Friday.

Maximum sustained winds are near 140 mph (220 km/h) with higher gusts. Florence is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Strengthening is forecast tonight and Wednesday. While some weakening is expected on Thursday, Florence is forecast to be an extremely dangerous major hurricane through landfall.

Hurricane-force winds extend outward up to 60 miles (95 km) from the center and tropical-storm-force winds extend outward up to 175 miles (280 km).

The estimated minimum central pressure is 945 mb (27.91 inches).

HAZARDS AFFECTING LAND
———————-
STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground if peak surge occurs at the time of high tide…

Cape Fear to Cape Lookout, including:

Neuse and Pamlico Rivers…9-13 ft
North Myrtle Beach to Cape Fear…6-9 ft
Cape Lookout to Ocracoke Inlet…6-9 ft
South Santee River to North Myrtle Beach…4-6 ft
Ocracoke Inlet to North Carolina/Virginia Border…4-6 ft
Edisto Beach to South Santee River…2-4 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: Florence is expected to produce total rainfall accumulations of 15 to 25 inches with isolated maximum amounts of 35 inches near the storm’s track over portions of the Carolinas and Mid-Atlantic States from late this week into early next week. This rainfall would produce catastrophic flash flooding and significant river flooding.

WIND: Hurricane conditions are expected to reach the coast within the hurricane warning area on Friday. Winds are expected to first reach tropical storm strength on Thursday, making outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

SURF: Swells generated by Florence are affecting Bermuda and portions of the U.S. East Coast. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

NWS National Hurricane Center Miami FL 500 PM AST Tue Sep 11 2018

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...27.5N 67.1W
ABOUT 360 MI...580 KM SSW OF BERMUDA
ABOUT 785 MI...1260 KM ESE OF CAPE FEAR NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...140 MPH...220 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...945 MB...27.91 INCHES

WATCHES AND WARNINGS

CHANGES WITH THIS ADVISORY: A Storm Surge Warning has been issued from South Santee River, South Carolina, to Duck, North Carolina, and the Albemarle and Pamlico Sounds, including the Neuse and Pamlico Rivers. A Hurricane Warning has been issued from South Santee River, South Carolina, to Duck, North Carolina, and the Albemarle and Pamlico Sounds. A Tropical Storm Watch has been issued from north of the North Carolina/Virginia border to Cape Charles Light, Virginia, and for the Chesapeake Bay south of New Point Comfort.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for… * South Santee River South Carolina to Duck North Carolina * Albemarle and Pamlico Sounds, including the Neuse and Pamlico Rivers A Storm Surge Watch is in effect for… * Edisto Beach South Carolina to South Santee River South Carolina * North of Duck North Carolina to the North Carolina/Virginia border.

A Hurricane Warning is in effect for… * South Santee River South Carolina to Duck North Carolina * Albemarle and Pamlico Sounds

A Hurricane Watch is in effect for… * Edisto Beach South Carolina to South Santee River South Carolina * North of Duck North Carolina to the North Carolina/Virginia border

A Tropical Storm Watch is in effect for… * North of the North Carolina/Virginia border to Cape Charles Light Virginia * Chesapeake Bay south of New Point Comfort Interests elsewhere in the southeastern and mid-Atlantic states should monitor the progress of Florence. Additional watches and warnings may be required tonight or Wednesday.

A Storm Surge Warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline, during the next 36 hours in the indicated locations. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. This is a life-threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.

A Storm Surge Watch means there is a possibility of life- threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area.

A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm- force winds, conditions that make outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

Hurricane Florence Arrival Tropical Force Winds 1700 Hours September 11 2018

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.

DISCUSSION AND OUTLOOK

At 500 PM AST (2100 UTC), the center of the eye of Hurricane Florence was located by satellite near latitude 27.5 North, longitude 67.1 West. Florence is moving toward the west-northwest near 17 mph (28 km/h). A motion toward the west-northwest and northwest is expected through early Thursday. Florence is expected to slow down considerably by late Thursday into Friday. On the forecast track, the center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas through Wednesday, and approach the coast of North Carolina or South Carolina in the hurricane warning area on Thursday and Friday.

Maximum sustained winds have increased to near 140 mph (220 km/h) with higher gusts. Florence is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Further strengthening is forecast tonight and Wednesday. While some weakening is expected on Thursday, Florence is forecast to be an extremely dangerous major hurricane through landfall. Hurricane-force winds extend outward up to 60 miles (95 km) from the center and tropical-storm-force winds extend outward up to 175 miles (280 km). The estimated minimum central pressure is 945 mb (27.91 inches).

HAZARDS AFFECTING LAND

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground if peak surge occurs at the time of high tide… Cape Fear to Cape Lookout, including the Neuse and Pamlico Rivers…9-13 ft North Myrtle Beach to Cape Fear…6-9 ft Cape Lookout to Ocracoke Inlet…6-9 ft South Santee River to North Myrtle Beach…4-6 ft Ocracoke Inlet to North Carolina/Virginia Border…4-6 ft Edisto Beach to South Santee River…2-4 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: Florence is expected to produce total rainfall accumulations of 15 to 25 inches with isolated maximum amounts of 35 inches near the storm’s track over portions of the Carolinas and Mid-Atlantic States from late this week into early next week. This rainfall would produce catastrophic flash flooding and significant river flooding.

WIND: Hurricane conditions are expected to reach the coast within the hurricane warning area on Friday. Winds are expected to first reach tropical storm strength on Thursday, making outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion. SURF: Swells generated by Florence are affecting Bermuda and portions of the U.S. East Coast. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

NWS National Hurricane Center Miami FL 200 PM AST Tue Sep 11 2018

A Storm Surge Watch is in effect for… * Edisto Beach South Carolina to the North Carolina-Virginia border * Albemarle and Pamlico Sounds, including the Neuse and Pamlico Rivers A Hurricane Watch is in effect for… * Edisto Beach South Carolina to the North Carolina-Virginia border * Albemarle and Pamlico Sounds Interests elsewhere in the southeastern and mid-Atlantic states should monitor the progress of Florence. Additional watches may be required later today.

A Storm Surge Watch means there is a possibility of life- threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.

DISCUSSION AND OUTLOOK

At 200 PM AST (1800 UTC), the eye of Hurricane Florence was located near latitude 27.1 North, longitude 66.2 West. Florence is moving toward the west-northwest near 17 mph (28 km/h). A west- northwestward to northwestward motion with a slight increase in forward speed are expected during the next couple of days. On the forecast track, the center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas through Wednesday, and approach the coast of North Carolina or South Carolina in the hurricane watch area Thursday and Friday.

Maximum sustained winds are near 130 mph (215 km/h) with higher gusts. Florence is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Florence is expected to begin re- strengthening later today and continue a slow strengthening trend for the next day or so. While some weakening is expected on Thursday, Florence is expected to be an extremely dangerous major hurricane through landfall.

Hurricane-force winds have expanded outward and now extend up to 60 miles (95 km) from the center.

Tropical-storm-force winds have also expanded and now extend outward up to 170 miles (280 km) from the center.

The estimated minimum central pressure is 950 mb (28.06 inches).

HAZARDS AFFECTING LAND

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground if peak surge occurs at the time of high tide… Edisto Beach to Murrells Inlet…2-4 ft Murrells Inlet to Cape Fear…4-6 ft Cape Fear to Cape Lookout including The Neuse and Pamlico River…6-12 ft Cape Lookout to Ocracoke Inlet…5-8 ft Ocracoke Inlet to North Carolina/Virginia Border…3-5 ft The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

RAINFALL: Florence is expected to produce total rainfall accumulations of 15 to 20 inches with isolated maximum amounts to 30 inches near the storm’s track over portions of the Carolinas and Mid-Atlantic States from late this week into early next week. This rainfall could produce catastrophic flash flooding and significant river flooding.

WIND: Hurricane conditions are possible within the watch area by late Thursday or Thursday night, with tropical storm conditions possible by Thursday morning.

SURF: Swells generated by Florence are affecting Bermuda and portions of the U.S. East Coast. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

NWS National Hurricane Center Miami FL 1100 AM AST Tue Sep 11 2018

Hurricane Florence Data from satellites and an Air Force Reserve reconnaissance aircraft mission indicate that Florence has completed an overnight eyewall replacement cycle (ERC). The recon data indicate that the eye has now expanded to a diameter of 30-32 n mi, and this was confirmed by an 1103Z SSMI/S microwave satellite image. The aircraft provided various intensity estimates with a peak SFMR surface wind of 113 kt noted in the northwest quadrant, a peak 700-mb flight-level wind of 143 kt in the northeast quadrant, and a central pressure of 950 mb. The 143-kt flight-level wind would normally correlate to an equivalent surface wind of about 129 kt. However, coincident SFMR surface winds were only 108 kt, indicating that the weak convection that region of the hurricane was not vigorous enough to bring down the strongest winds to the surface. The 950-mb central pressures corespondents to about 113 kt. Based on a blend of all these data, the initial intensity has been set to 115 kt.

The initial motion estimate is now 295/14 kt based on the recent recon fix data. The broken record continues — there is no significant to the previous track forecast or reasoning. Although the global and regional models continue to make minor shifts northward and southward, the consensus models have changed little. GOES-16 high-resolution water vapor imagery indicates that the amplifying large-scale flow pattern across CONUS is inducing a downstream ridge over the western Atlantic, with a high pressure cell centered northwest of Bermuda. This blocking ridge pattern is expected to keep Florence moving west-northwestward to northwest at around 15 kt for the next 48 hours or so. However, embedded within the large-scale flow is a weak shortwave trough over the central and southern Plains that is expected to eject out northeastward and weaken the ridging across the mid-Atlantic and southeastern U.S., causing Florence to slow down significantly in 72 hours as the powerful hurricane approaches the Carolinas.

On days 4 and 5, an even slower motion or drift to the west and northwest is forecast, which will exacerbate the heavy rainfall threat. The new NHC forecast track is just an update of the previous one, and basically lies the middle of the guidance envelope between the consensus models TVCA to the north and HCCA and FSSE to the south.

Hurricane Florence Rainfall 0800 Hours September 11 2018
Hurricane Florence Rainfall 0800 Hours September 11 2018

Water vapor imagery indicates that Florence has finally developed the much anticipated dual outflow pattern, with outflow jets noted in the northwestern and eastern quadrants. The latter outflow jet is flowing into an upper-level low, which is acting as an impressive mass sink near 25N/49W. These two outflow channels are producing significant deformation stretching across Florence’s inner-core, which should aid in the re-strengthening process. Now that the eye has become stable with a diameter of about 30 n mi and since Florence is expected to remain in a low-shear environment of around 5 kt and over above-average SSTs of 29.0-29.5 deg C, slow but steady strengthening is expected for the next 24-36 hours. By 48 h and beyond, Florence’s slow forward speed, coupled with the large eye and relatively shallow depth of the warm water should induce some upwelling beneath the cyclone that will initiate a slow weakening trend. By 72 hours the vertical wind shear is expected to increase to near 20 kt from the southwest, which will cause more significant weakening to occur. However, given the large overall wind field of Florence along with the large eye, only gradual weakening is expected. Once Florence moves inland, the slow forward speed of 3-5 kt will result in rapid spin down and weakening of the wind field. The new official intensity forecast is above of all of the intensity guidance based on the aforementioned very favorable synoptic outflow pattern, and to maintain continuity with the previous forecast.

Key Messages:

1. A life-threatening storm surge is likely along portions of the coastlines of South Carolina, North Carolina, and Virginia, and a Storm Surge Watch is in effect for a portion of this area. All interests from South Carolina into the mid-Atlantic region should ensure they have their hurricane plan in place and follow any advice given by local officials.

2. Life-threatening, catastrophic flash flooding and significant river flooding is possible over portions of the Carolinas and Mid-Atlantic states from late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Watch is in effect for a part of this area. Damaging winds could also spread well inland into portions of the Carolinas and Virginia.

4. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 26.7N  65.3W  115 KT 130 MPH - Category 4 (ESE Coopers Town, Bahamas)
 12H  12/0000Z 27.7N  67.6W  120 KT 140 MPH - Category 4 (ESE Coopers Town, Bahamas)
 24H  12/1200Z 29.4N  70.6W  130 KT 150 MPH - Category 4 (ESE St. Augustine, FL)
 36H  13/0000Z 31.1N  73.1W  130 KT 150 MPH - Category 4 (ESE Charleston, SC)
 48H  13/1200Z 32.6N  75.2W  120 KT 140 MPH - Category 4 (ESE Myrtle Beach, SC)
 72H  14/1200Z 34.2N  77.1W  105 KT 120 MPH - Category 3 (ENE Wrightsville Beach, NC)
 96H  15/1200Z 35.0N  78.1W   40 KT  45 MPH - Tropical Storm (Warsaw, NC)
120H  16/1200Z 35.5N  79.5W   25 KT  30 MPH - Tropical Storm (High Falls, NC)

NWS National Hurricane Center Miami FL 500 AM AST Tue Sep 11 2018

Recent satellite imagery shows that the eye of Florence  has become cloud filled and an earlier 0441 UTC microwave overpass revealed a double eyewall structure. These observations suggest that an eyewall replacement cycle is likely underway. Subjective and objective Dvorak current intensity numbers have not changed so the initial intensity will remain 120 kt for this advisory. An Air Force Reserve Hurricane Hunter mission is en route to the storm and should provide a better assessment of Florence’s structure and intensity this morning. NOAA buoy 41049 located about 80 nmi north of the eye, has reported tropical-storm-force winds during the last several hours and seas as high as 23 ft.

Florence’s upper-level environment is predicted to remain quite favorable while the storm traverses sea surface temperatures of around 29C over the next 48 hours. Additional strengthening is forecast during this time, but some fluctuations in intensity are likely due to eyewall replacement cycles. The updated NHC intensity forecast once again calls for additional intensification and brings Florence to near category 5 strength within the next 24 to 36 hours. After 48 hours, a slight increase in southwesterly shear could result in some weakening, but Florence is expected to remain an extremely dangerous hurricane when it approaches the U.S. coastline. Florence has accelerated as anticipated and is now moving west-northwestward or 290 degrees at 13 kt. The track forecast reasoning has not changed much. A mid-level ridge to the northeast of Bermuda is expected steer Florence quickly west-northwestward to northwestward toward the southeast United States coast over the next 2 to 3 days.

Hurricne Florence Tropical Force Wind Arrival Times 0500 Hours September 11 2018
Hurricne Florence Tropical Force Wind Arrival Times 0500 Hours September 11 2018

By 72 hours, a high pressure ridge building over the Upper-Midwest and Great Lakes regions is forecast to cause a significant reduction in Florence’s forward speed and the hurricane is predicted to meander over the eastern portions of North or South Carolina at days 4 and 5. The ECMWF has trended slower this cycle at days 4 and 5, and as a result the NHC forecast shows slightly less motion at those time periods. The spread in the guidance increases by 72 hours, with the GFS and its ensemble mean along the right side of the guidance, while the ECMWF remains along the left edge. It should be noted that there are still a number of ECMWF members that are even farther left. The NHC track forecast has been nudged to the left and is close to the TVCN consensus aid. Given the amount of uncertainty by day 3, it is important not to focus on the exact forecast track as average NHC errors at days 3, 4, and 5 are about 100, 140 and 180 n mi, respectively, and dangerous hazards will extend well away from the center. Storm Surge and Hurricane watches have been issued for a portion of the coast of South and North Carolina. Additional Hurricne Florence Wind Speed Probability 0800 Hours September 11 2018watches may be required later today.

Key Messages:

1. A life-threatening storm surge is likely along portions of the coastlines of South Carolina, North Carolina, and Virginia, and a Storm Surge Watch has been issued for a portion of this area. All interests from South Carolina into the mid-Atlantic region should ensure they have their hurricane plan in place and follow any advice given by local officials.

2. Life-threatening freshwater flooding is likely from a prolonged and exceptionally heavy rainfall event, which may extend inland over the Carolinas and Mid Atlantic for hundreds of miles as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Watch has been issued for a part of this area. Damaging winds could also spread well inland into portions of the Carolinas and Virginia.

4. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  11/0900Z 26.4N  64.1W  120 KT 140 MPH - Category 4 (ESE Coopers Town, Bahamas)
 12H  11/1800Z 27.2N  66.4W  125 KT 145 MPH - Category 4 (ESE Coopers Town, Bahamas)
 24H  12/0600Z 28.7N  69.4W  130 KT 150 MPH - Category 4 (ENE Coopers Town, Bahamas)
 36H  12/1800Z 30.5N  72.2W  130 KT 150 MPH - Category 4 (ESE Jacksonville, FL)
 48H  13/0600Z 32.2N  74.5W  125 KT 145 MPH - Category 4 (ESE Myrtle Beach, SC)
 72H  14/0600Z 34.3N  77.1W  115 KT 130 MPH - Category 4 (ESE Topsail Beach, NC)
 96H  15/0600Z 35.2N  78.0W   45 KT  50 MPH - Tropical Storm (Williams, NC)
120H  16/0600Z 36.0N  79.0W   25 KT  30 MPH - Tropical Storm (Arrowhead, Durham, NC)

NWS National Hurricane Center Miami FL 1100 AM AST Mon Sep 10 2018

Florence  is quickly becoming a powerful hurricane. Satellite images show that the distinct eye has warmed in the center, with convection increasing in the eyewall during the past several hours. The initial wind speed is set to 100 kt, closest to the CIMSS-ADT value. A NOAA Hurricane Hunter will be in the area later this morning for a more accurate estimate.

The hurricane is moving over progressively warmer waters over the next couple of days, with water temperatures peaking near 85F. In combination with the low vertical wind shear in the forecast during that time, Florence should continue to strengthen, and all models show it becoming a category 4 hurricane by tomorrow. The corrected-consensus guidance has done quite well with this intensification episode, and I don’t see any reason to deviate much from them at this time. As Florence approaches the southeastern United States, there will likely be fluctuations in intensity from eyewall cycles, but even if this occurs, the hurricane’s wind field is expected to grow with time, increasing the storm surge and inland wind threats. The bottom line is that there is increasing confidence that Florence will be a large and extremely dangerous hurricane, regardless of its exact intensity.

During the last several hours, Florence has turned westward again, estimated at 11 kt. The steering currents are becoming well- defined as as a very strong ridge builds over the northwestern Atlantic Ocean, forcing Florence to move faster toward the west-northwest during the next couple of days. By late Wednesday, a turn toward the northwest is possible due to the orientation of the Atlantic ridge, along with a slight decrease in forward speed due to a new ridge building over the Great Lakes. The various models are shifting around at long range, but the model consensus has barely budged in the past few model cycles. Thus the new NHC forecast is close to the previous one, near the NOAA and FSSE consensus guidance. It is important not to focus on the exact forecast track as average NHC errors at days 4 and 5 are about 140 and 180 n mi, respectively, and dangerous hazards will extend well away from the center.

Key Messages:

1. A life-threatening storm surge is likely along portions of the coastlines of South Carolina, North Carolina, and Virginia, and a Storm Surge Watch will likely be issued for some of these areas by Tuesday morning. All interests from South Carolina into the mid-Atlantic region should ensure they have their hurricane plan in place and follow any advice given by local officials.

2. Life-threatening freshwater flooding is likely from a prolonged and exceptionally heavy rainfall event, which may extend inland over the Carolinas and Mid Atlantic for hundreds of miles as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Watch will likely be issued by Tuesday morning. Damaging winds could also spread well inland into portions of the Carolinas and Virginia.

4. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 25.0N  60.0W  100 KT 115 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 12H  11/0000Z 25.5N  61.9W  115 KT 130 MPH - Category 4 (ENE Coopers Town, Bahamas)
 24H  11/1200Z 26.4N  64.7W  125 KT 145 MPH - Category 4 (ESE Coopers Town, Bahamas)
 36H  12/0000Z 27.8N  67.9W  130 KT 150 MPH - Category 4 (ENE Melbourne, FL)
 48H  12/1200Z 29.5N  71.0W  130 KT 150 MPH - Category 4 (ESE St. Augustine, FL)
 72H  13/1200Z 33.0N  76.3W  125 KT 145 MPH - Category 4 (ESE Myrtle Beach, SC)
 96H  14/1200Z 35.0N  79.0W   75 KT  85 MPH - Category 1 (Fayetteville, NC)
120H  15/1200Z 36.0N  80.0W   30 KT  35 MPH - Tropical Storm (High Point, NC)

NWS National Hurricane Center Miami FL 500 AM AST Mon Sep 10 2018

Corrected to reflect that the 96 hour forecast point is inland. Florence   is rapidly strengthening this morning. The satellite presentation has improved markedly overnight with a small 10-n-mi wide-eye becoming apparent in infrared satellite pictures. The upper-level outflow continues to expand over the northern and northwestern portions of the storm, but is somewhat restricted over the southeastern quadrant. Dvorak satellite classifications from TAFB and SAB supported an intensity of around 80 kt at 0600 UTC, but with the cooling of the cloud tops around the eye since that time, the initial intensity has been increased to 90 kt for this advisory.

Satellite fixes indicate that Florence has turned west-northwestward (285 degrees), and is moving at a slightly faster forward speed of 8 kt. A high pressure ridge building to the north and northwest of Florence is expected to steer the hurricane west-northwestward to northwestward at a much faster forward speed over the southwest Atlantic during the next few days. After that time, a building ridge over the Ohio Valley is expected to cause a gradual reduction in the forward speed of the cyclone as it approaches the southeastern United States coastline. The latest run of the ECMWF has shifted southwestward, along with its ensemble suite, while there was little overall change in the GFS and its ensemble. On the other hand, the UKMET shifted northeastward and is now along the right side of the guidance envelope. With these changes to the guidance, the overall spread has increased this cycle, however, the corrected consensus aids (FSSE and HCCA) are not much different than before, and the NHC track again follows these models very closely. Users are cautioned to not focus on the exact forecast track as the average NHC errors at days 4 and 5 are about 140 and 180 n mi, respectively.

Hurricane Florence Tropical Force Winds 0500 Hours September 10 2018
Hurricane Florence Tropical Force Winds 0500 Hours September 10 2018

Florence will be traversing very warm SSTs of around 29C and remain within a very favorable upper-level environment during the next couple of days. These conditions are expected to lead to significant strengthening during the next 12 to 24 hours, and Florence is forecast to be a very powerful major hurricane on its approach to the southeastern United States. The NHC intensity forecast is slightly above all of the intensity guidance during the first 24 hours, and is then a blend of the FSSE and HCCA models. The global model guidance also increases the size of Florence’s wind field during the next few days, and this has been reflected in the NHC wind radii forecast.

The NOAA G-IV jet is conducting another synoptic surveillance mission this morning in support of the 1200 UTC model cycle, and these flights will continue through Tuesday. A NOAA P-3 Hurricane Hunter aircraft is also scheduled to conduct a research mission into Florence this morning, with Air Force C-130 fix missions beginning late this afternoon. Additional upper-air data are being collected across portions of the central and eastern U.S. via special 0600 UTC and 1800 UTC radiosonde launches. Hopefully these data will help improve the track and intensity forecasts.

Hurricane Florence Earliest Arrival Time Tropical Force Winds 0500 Hours September 10 2018Key Messages:

1. There is an increasing risk of life-threatening impacts from Florence: storm surge at the coast, freshwater flooding from a prolonged and exceptionally heavy rainfall event inland, and damaging hurricane-force winds. While it is too soon to determine the exact timing, location, and magnitude of these impacts, interests at the coast and inland from South Carolina into the mid-Atlantic region should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials.

2. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week. These swells will result in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0900Z 24.9N  58.9W   90 KT 105 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 12H  10/1800Z 25.4N  60.5W  110 KT 125 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 24H  11/0600Z 26.1N  63.1W  120 KT 140 MPH - Category 4 (ENE Coopers Town, Bahamas)
 36H  11/1800Z 27.3N  66.2W  125 KT 145 MPH - Category 4 (ENE Coopers Town, Bahamas)
 48H  12/0600Z 28.8N  69.3W  130 KT 150 MPH - Category 4 (E Daytona Beach, Florida)
 72H  13/0600Z 32.2N  74.8W  125 KT 145 MPH - Category 4 (E Kiawah. South Carolina)
 96H  14/0600Z 34.5N  78.1W  100 KT 115 MPH - Category 3 ( Yamacraw, North Carolina)
120H  15/0600Z 35.8N  79.6W   40 KT  45 MPH - Tropical Storm (Liberty, North Carolina)

NWS National Hurricane Center Miami FL 1100 PM AST Sun Sep 09 2018

Florence’ssatellite appearance has continued to improve quite markedly since the previous advisory. An eye was evident in GOES-16 high-resolution infrared imagery and other channels between 2300-0000 UTC, but it became cloud covered immediately thereafter due to a strong burst of deep convection in the southern and eastern eyewall where cloud tops colder than -80C and an abundance of lightning activity was observed. Since that time, the CDO has expanded and become more circular, outflow has increased and become more symmetrical, and an eye has begun to re-appear. The initial intensity has been increased to 80 kt for this advisory based on a subjective Dvorak intensity estimate of T4.5/77 kt from SAB and NHC objective intensity estimates ranging from 77 kt to 87 kt.

The initial motion estimate is 280/06 kt. Once again, there is no significant change to the previous forecast track or synoptic reasoning. The models appear to be getting better dialed in on both the location and strength of the developing blocking ridge in the vicinity of Bermuda during the next 4 days as the mid-latitude flow amplifies across the CONUS and the northwestern Atlantic. In fact, the global models are now in very good agreement on forecasting Florence’s upper-level mass outflow being deposited to the north and east of the hurricane, which will act to further strengthen the blocking ridge and help to drive the hurricane northwestward toward the southeastern U.S. coastal region. The new NHC model guidance is even more tightly packed about the previous forecast track, with less than a 90 n mi cross-track spread at 72 h and less than 120 n mi spread at 96 h, just prior to expected landfall. Therefore, the new official advisory track is essentially just an update and extension of the previous forecast, and lies between the nearly juxtaposed HCCA and FSSE corrected consensus track models.Hurricane Florence Tropical Force Winds 2300 Hours September 9 2018

Now that Florence has developed an inner-core ring of deep convection, which has insulated the eye from intrusions of dry air, rapid intensification appears likely to begin soon and continue for the next 36 hours or so due to the expected very low vertical wind shear conditions, dual outflow jet pattern that will be developing, and very warm SSTs of 29-29.5 deg C beneath the hurricane. The most favorable combination of the aforementioned factors will occur in about 48 h, and that’s when Florence is likely to achieve its maximum intensity. After 72 hours, the wind shear is expected to increase to around 10-15 kt from the south or southwest, and the dual outflow pattern is forecast to change to only a single poleward outflow pattern. This slight degradation in the upper-level environment, along with slightly cooler SSTs, is expected to result in a gradual weakening of the powerful cyclone. However, Florence is still forecast to be near category-4 strength when the dangerous hurricane makes landfall. The official intensity forecast is an average of the intensity forecast from the corrected consensus models HCCA and FSSE, with the latter explicitly forecasting a peak intensity of 134 kt in 72 hours. It is also worth noting that the model guidance is also significantly increasing the size of Florence’s wind field over the next few days, and the official forecast reflects this trend.

The NOAA G-IV jet will conduct another synoptic surveillance mission early Monday morning in support of the 1200 UTC model cycle, and these flights will continue through Tuesday. In addition, upper-air stations across portions of the central and eastern U.S. are conducting special 0600 UTC and 1800 UTC radiosonde launches to collect extra data for the numerical models. Hopefully these data will help improve the track and intensity forecasts.

Key Messages:

1. There is an increasing risk of two life-threatening impacts from Florence: storm surge at the coast and freshwater flooding from a prolonged heavy rainfall event inland. While it is too soon to determine the exact timing, location, and magnitude of these impacts, interests at the coast and inland from South Carolina into the mid-Atlantic region should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials.

2. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week. These swells will result in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 24.6N  57.7W   80 KT  90 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 12H  10/1200Z 24.9N  59.1W   90 KT 105 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 24H  11/0000Z 25.6N  61.5W  105 KT 120 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 36H  11/1200Z 26.5N  64.4W  120 KT 140 MPH - Category 4 (ENE Coopers Town, Bahamas)
 48H  12/0000Z 27.8N  67.6W  130 KT 150 MPH - Category 4 (ENE Coopers Town, Bahamas)
 72H  13/0000Z 31.2N  73.6W  130 KT 150 MPH - Category 4 (SE Savannah, GA)
 96H  14/0000Z 34.0N  77.5W  120 KT 140 MPH - Category 4 (E Carolina Beach, NC)
120H  15/0000Z 35.2N  79.0W   55 KT  65 MPH - Tropical Storm (Pine Forest, Linden, NC)

NWS National Hurricane Center Miami FL 500 PM AST Sun Sep 09 2018
Hurricane Florence – The last reconnaissance fix indicated that the pressure had fallen to about 978 mb with Florence, a drop of about 6 mb in 4 hours, with uncontaminated SFMR winds of about 70 kt. Since then, the satellite presentation has continued to improve, with intensifying deep convection near the center. Thus the wind speed is set to 75 kt on this advisory. Radar data from the NOAA Hurricane Hunter indicated that there were still a few breaks in the eyewall,
possibly allowing some dry air to mix into the core. This structure has potentially kept Florence from intensifying rapidly so far. It is likely, however, that the eyewall will close soon with low environmental shear present, resulting in a faster intensification rate. The guidance is remarkably well clustered, with all of the hurricane models showing category 4 strength within 48 hours, which is uncommon given the current intensity.

The new forecast continues to show rapid intensification and is increased 5 or 10 kt at most time periods, but it is still not as high as the Florida State Superensemble or the NOAA corrected consensus models. It is worth noting that the model guidance is also significantly increasing the size of Florence’s wind field over the next few days, and the official forecast reflects this trend. The fixes from the aircraft indicate that Florence hasn’t gained much latitude yet, and continues moving westward at about 6 kt. There is no change to the synoptic reason as a very strong ridge is forecast to build over the northwestern Atlantic during the next few days. This pattern should steer Florence west-northwestward at a much faster forward speed by Tuesday. On Wednesday, the hurricane will likely turn northwestward and slow down somewhat due to another ridge forming over the Ohio Valley.

The most notable change from the previous advisory is that most of the models are showing a faster motion in 3 or 4 days, which unfortunately increases the risk of a destructive hurricane landfall. The GFS and its ensemble mean are outliers from the main model envelope, showing the system near the Outer Banks , while the rest of the guidance is well to the southwest. While a near-miss isn’t impossible given the spread of the ECMWF Ensemble, there is much more support for a track to the southwest, especially considering the poleward bias of the GFS thus far this season. Therefore, the official track forecast is shifted a little bit to the southwest, and is very close to the corrected-consensus models.

The NOAA G-IV jet is conducting a synoptic surveillance mission this afternoon to gather data near and around Florence for assimilation into the numerical models, and these missions will continue through Tuesday. In addition, upper-air stations across portions of the central and eastern U.S. are conducting special 0600 UTC and 1800 UTC radiosonde launches to collect extra data for the numerical models. Hopefully these data will help improve the track and intensity forecasts. Key Messages: 1. There is an increasing risk of two life-threatening impacts from Florence: storm surge at the coast and freshwater flooding from a prolonged heavy rainfall event inland. While it is too soon to determine the exact timing, location, and magnitude of these impacts, interests at the coast and inland from South Carolina into the mid-Atlantic region should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials. 2. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week. These swells will result in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  09/2100Z 24.4N  57.0W   75 KT  85 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 12H  10/0600Z 24.6N  58.3W   90 KT 105 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 24H  10/1800Z 25.1N  60.4W  105 KT 120 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 36H  11/0600Z 25.9N  63.1W  115 KT 130 MPH - Category 4 (ESE Tucker's Town, Bermuda)
 48H  11/1800Z 27.0N  66.2W  125 KT 145 MPH - Category 4 (ENE Coopers Town, Bahamas)
 72H  12/1800Z 30.3N  72.6W  130 KT 150 MPH - Category 4 (E Jacksonville, FL)
 96H  13/1800Z 33.5N  77.5W  120 KT 140 MPH - Category 4 (SE Myrtle Beach, SC)
120H  14/1800Z 35.0N  79.0W   60 KT  70 MPH - Tropical Storm (Fayetteville, NC)

NWS National Hurricane Center Miami FL 1100 AM AST Sun Sep 09 2018

Satellite images indicate that Florence  is strengthening. Deep convection has intensified in the central dense overcast, with hints of a ragged eye in the latest GOES-16 visible channel. The NOAA Hurricane Hunters just flew through the eye, finding 70 kt winds at flight-level and 66 kt from the SFMR. This data confirms that Florence has become a hurricane again, and the initial wind speed is set to 65 kt. The aircraft also found that the minimum pressure has decreased to 984 mb.

Overnight microwave data and the Hurricane Hunter vortex message show that a mostly complete eyewall has formed with Florence . In combination with low vertical wind shear and progressively warmer waters near 29C, this structure is a blueprint for rapid intensification. Almost all of the intensity guidance is showing at least one period of rapid strengthening during the next few days, which is rather rare. The NHC wind speed forecast is raised in the first couple of days following the guidance trend, then is very similar to the previous one. All indications are that Florence will be an extremely dangerous Category 4 hurricane while it moves over the western Atlantic toward the southeastern United States.

Hurricane Florence Wind Speeds Sept 9 to Sept 14 2018
Hurricane Florence Wind Speeds Sept 9 to Sept 14 2018

Florence continues moving slowly westward, caught between a pair of mid-level ridges over the Atlantic Ocean. A very strong ridge is forecast to build over the northwestern Atlantic during the next few days, which should steer Florence west-northwestward at a much faster forward speed. By Wednesday, the hurricane should turn northwestward, and slow down somewhat due to another ridge forming over the Ohio Valley. It is interesting to note that while the ensemble means from the ECMWF and UKMET are west of the NHC forecast, the strongest members are on the right side of their ensemble envelope. Thus, the new NHC track forecast is very similar to the previous one, and continues to lie between the corrected consensus and consensus aids. The Ohio Valley ridge is concerning because Florence could stop moving pretty quickly around day 5, potentially leading to a serious heavy rain episode and inland flood hazard.

Key Messages:

1. There is an increasing risk of two life-threatening impacts from Florence: storm surge at the coast and freshwater flooding from a prolonged heavy rainfall event inland. While it is too soon to determine the exact timing, location, and magnitude of these impacts, interests at the coast and inland from South Carolina into the mid-Atlantic region should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials.

FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 24.4N  56.3W   65 KT  75 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 12H  10/0000Z 24.5N  57.4W   80 KT  90 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 24H  10/1200Z 24.9N  59.3W   95 KT 110 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 36H  11/0000Z 25.6N  61.7W  105 KT 120 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 48H  11/1200Z 26.4N  64.5W  120 KT 140 MPH - Category 4 (ESE Tucker's Town, Bermuda)
 72H  12/1200Z 29.0N  70.8W  125 KT 145 MPH - Category 4 (ESE Daytona Beach, Florida)
 96H  13/1200Z 32.2N  75.8W  120 KT 140 MPH - Category 4 (ESE ESE Charleston, South Carolina)
120H  14/1200Z 35.0N  78.5W   85 KT 100 MPH - Category 1 (Salemburg, North Carolina)

NWS National Hurricane Center Miami FL 500 AM AST Sun Sep 09 2018

Florence’s cloud pattern has continued to gradually become better organized overnight, with an increase in convection near the center and a developing central dense overcast feature. However, the cloud tops are not particularly cold and the outer banding features remain fragmented likely due to some nearby dry mid-level air. Dvorak intensity estimates from TAFB and SAB range from 55 to 65 kt, so the initial intensity remains 60 kt, just shy of hurricane strength. The NOAA Hurricane Hunters are scheduled to investigate the storm later today, and that data should provide a better assessment of Florence’s intensity.

The upper-level outflow is becoming well established over the cyclone, and the global model guidance indicates that Florence will remain in a very favorable upper-level environment while the cyclone moves over the warm waters over the southwestern Atlantic. These conditions favor strengthening with the only apparent negative factor being nearby dry air, which will likely remain away from the inner core due to the low shear conditions. The NHC intensity forecast again calls for a period of rapid strengthening within the next 12-36 hours, and Florence is forecast to become a major hurricane on Monday with additional strengthening early in the week. This means that Florence is likely to be a very powerful hurricane as it moves over the western Atlantic toward the southeastern United States. The new NHC intensity forecast is near the various intensity consensus aids and is very similar to the previous official forecast.

Hurricane Florence Wind Speeds Sept 9 to Sept 14 2018
Hurricane Florence Wind Speeds Sept 9 to Sept 14 2018

Florence is currently located between a couple of mid-level ridges and a slow westward motion is expected today. Another strong high pressure ridge is forecast to build to the north of Florence on Monday, which should cause the storm to begin moving west-northwestward to northwestward at an increasingly faster forward speed. The dynamical model guidance is tightly clustered for the first 2-3 days with increasing spread thereafter. The GFS remains along the right side of the guidance envelope with the HWRF and ECMWF bracketing the left edge. It should be noted that both the GFS and ECMWF ensemble means are a little to the left or west of their operational runs. As a result, the NHC track forecast lies to the left of the TVCA multi-model consensus, but is not as far to the west as the FSSE and HCCA corrected consensus models at day 5. The models are in agreement that Florence is likely to slow down near the end of the forecast period as a blocking high pressure ridge builds to the north of the hurricane.

Key Messages:

1. Florence is forecast to be a dangerous major hurricane near the southeast U.S. coast by late this week, and the risk of direct impacts continues to increase. However, given the uncertainty in track and intensity forecasts at those time ranges, it’s too soon to determine the exact timing, location, and magnitude of those impacts.

2. Interests along the U.S. East Coast, particularly from north Florida through North Carolina, should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials.

3. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week. These swells will result in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0900Z 24.5N  55.8W   60 KT  70 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 12H  09/1800Z 24.6N  56.7W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 24H  10/0600Z 24.8N  58.3W   85 KT 100 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 36H  10/1800Z 25.3N  60.4W  100 KT 115 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 48H  11/0600Z 26.1N  63.1W  110 KT 125 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 72H  12/0600Z 28.2N  69.1W  125 KT 145 MPH - Category 4 (WSW Tucker's Town, Bermuda)
 96H  13/0600Z 31.3N  74.8W  120 KT 140 MPH - Category 4 (ESE Charleston, South Carolina)
120H  14/0600Z 34.4N  77.9W  105 KT 120 MPH - Category 3 (Rocky Point, North Carolina)

NWS National Hurricane Center Miami FL 1100 PM AST Sat Sep 08 2018

Satellite images indicate that the cloud pattern has continued to gradually become better organized with an eye feature trying to form. An average of all of the Dvorak satellite intensity estimates tonight suggest that Florence is not a hurricane yet, but is close to being one. The initial intensity is kept at 60 kt in this advisory. The recent ASCAT data showed less winds than previously observed by the NOAA plane when the cloud pattern was less organized.

There is a band of convection trying to wrap around a possible eye feature, and that is an indication that Florence has continued to recover from the hostile shear environment, which brought the hurricane from Category 4 to a tropical storm in a matter of a day or so. The presence of developing upper-level outflow is a good indication that the shear has decreased, and with the presence of a warm ocean ahead, strengthening is anticipated. As indicated by my predecessor, the official forecast continues to call for a period of rapid intensification in about 12-24 hours, and Florence is expected to reach major hurricane intensity between 36-48 hours with additional strengthening thereafter. Florence is forecast to be an intense hurricane on days 3 through 5 as it moves across the warm waters of the southwestern Atlantic Ocean between the Bahamas and Bermuda, and then as it heads toward the southeast United States coast.Hurricane Florence Wind Speeds Sept 8 to Sept 13 2018

Florence is still trapped within very light steering currents, and is slowly moving toward the west or 270 degrees at 5 kt. All indications are that this is about to change, as a strong ridge of high pressure builds to the north of the hurricane. This forecast flow pattern predicted by the global models will force Florence on a general west-northwest to northwest track with an increase in forward speed. The NHC forecast is basically on top of the previous one, and is in the middle of the narrow guidance envelope mainly for the next 3 to 4 days. By the end of the forecast period, when the hurricane is approaching the U.S. coast, the guidance envelope is wider and becomes bounded by the northernmost GFS and the southernmost HCCA and the FSSE ensembles. One thing all models coincide at the longer range is with the collapsing of the steering currents, resulting in a significant reduction of the forward speed of the hurricane.

Hurricane Florence Wind Speed Arrival Time Projection 2300 Hours September 8 2018Key Messages:

1. Florence is forecast to be a dangerous major hurricane near the southeast U.S. coast by late next week, and the risk of direct impacts continues to increase. However, given the uncertainty in track and intensity forecasts at those time ranges, it’s too soon to determine the exact timing, location, and magnitude of those impacts.

2. Interests along the U.S. East Coast, particularly from north Florida through North Carolina, should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials.

3. Large swells affecting Bermuda and portions of the U.S. East Coast will continue into next week. These swells will result in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0300Z 24.6N  55.2W   60 KT  70 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 12H  09/1200Z 24.5N  55.9W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 24H  10/0000Z 24.8N  57.4W   80 KT  90 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 36H  10/1200Z 25.2N  59.3W  100 KT 115 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 48H  11/0000Z 25.8N  61.8W  110 KT 125 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 72H  12/0000Z 27.5N  67.5W  125 KT 145 MPH - Category 4 (E Coopers Town, Bahamas)
 96H  13/0000Z 30.0N  73.5W  125 KT 145 MPH - Category 4 (E St. Augustine. FL)
120H  14/0000Z 33.8N  77.8W  115 KT 130 MPH - Category 4 (E Frying Pan Shoals. NC)

NWS National Hurricane Center Miami FL 800 PM EDT Sat Sep 8 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical Storm Florence, located over the central Atlantic Ocean, on Tropical Storm Helene, located roughly about 150 miles southeast of the Cabo Verde Islands, and on newly upgraded Tropical Storm Isaac, located over the eastern Atlantic.

NWS National Hurricane Center Miami FL 500 PM AST Sat Sep 08 2018

A NOAA P3 aircraft conducted a research mission several hours ago in Florence  and measured SFMR surface winds of around 60 kt and winds up to 65 kt at a flight level of 8000 feet. Velocities of 65-70 kt at 500 meters were also measured by the Doppler radar on the plane. Based on these data, the initial wind speed is raised to 60 kt. Dropsonde data also showed that the central pressure was down to 989 mb.

Florence is slowly recovering from the dry air its circulation ingested while it was under the influence of strong shear. Convection in the outer bands is relatively thin but is deeper and more persistent near the center. Now that the shear has decreased and the warm waters ahead of Florence reach deeper into the ocean, continued strengthening is anticipated. In fact, the official forecast continues to show a period of rapid intensification, now beginning 12-24 hours, with Florence reaching major hurricane intensity between 36-48 hours. One fly in the ointment is that the SHIPS diagnostics are keeping mid-level relative humidities around the cyclone around 50 percent, which isn’t particularly moist, but I’m going to assume that Florence will be able to scour out the dry air within its circulation in the coming days. The HCCA model and the ICON intensity consensus support maintaining a forecast peak intensity of 125 kt in 4 days or so, so no significant changes were made from the previous forecast. Regardless of the specifics of the other models–some of which are higher and some of which are lower–Florence is expected to be a powerful major hurricane on days 3 through 5 as it moves across the southwestern Atlantic Ocean.Hurricane Florence Wind Speeds Sept 8 to Sept 13 2018

Florence is creeping westward (270 degrees) at 4 kt, trapped between high pressure to its northeast and southwest. A different blocking ridge is expected to develop north and northeast of Bermuda over the next few days, causing Florence to accelerate toward the west-northwest and northwest between days 3-5. There have been some notable shifts in the model guidance on this cycle, with the ECMWF model swinging to the northeast closer to the GFS, and the HWRF model swinging farther south along the southern edge of the guidance envelope. Despite this change in the deterministic ECMWF run, its individual ensemble members are still showing a significant spread of solutions from just north of the Bahamas to offshore the coast of North Carolina by day 5. Because of this spread, the updated NHC track forecast largely maintains continuity and remains close to the TVCN multi-model consensus. And despite the ECMWF’s shift, this track prediction remains north of the HCCA and FSSE solutions.

Earliest Arrival Time Tropical Force WindsKey Messages:

1. Florence is forecast to be a dangerous major hurricane near the southeast U.S. coast by late next week, and the risk of direct impacts continues to increase. However, given the uncertainty in track and intensity forecasts at those time ranges, it’s too soon to determine the exact timing, location, and magnitude of those impacts.

2. Interests along the U.S. East Coast, particularly from north Florida through North Carolina, should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials.

3. Large swells affecting Bermuda and portions of the U.S. East Coast will continue into next week. These swells will result in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 24.6N  54.7W   60 KT  70 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 12H  09/0600Z 24.6N  55.4W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 24H  09/1800Z 24.7N  56.6W   80 KT  90 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 36H  10/0600Z 25.0N  58.3W   95 KT 110 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 48H  10/1800Z 25.4N  60.5W  110 KT 125 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 72H  11/1800Z 26.9N  66.4W  120 KT 140 MPH - Category 4 (ENE North Palmetto Point, Bahamas)
 96H  12/1800Z 29.5N  72.5W  125 KT 145 MPH - Category 4 (E Daytona Beach, FL)
120H  13/1800Z 32.5N  77.0W  120 KT 140 MPH - Category 4 (E Charleston, SC)

NWS National Hurricane Center Miami FL 1100 AM AST Sat Sep 08 2018

Florence has undergone a dramatic structural evolution just within the past 6 hours or so. Vertical shear has decreased just enough for the storm to take on a more symmetric shape, with convection developing in a ring around the low-level center, and an elongated band wrapping around to the northeastern part of the circulation. The convection has waned a little bit in intensity, however, due to the presence of dry air, and Dvorak estimates support maintaining an initial intensity of 55 kt for now. A NOAA P-3 aircraft is approaching Florence now on a research mission and should provide some useful data to better assess the storm’s intensity.

Recent WindSat microwave data revealed that Florence has a well-defined low-level ring in the 37-GHz channel, which tends to be a harbinger of strengthening when environmental conditions are favorable. Since vertical shear is decreasing and should be 10 kt or less by later today, and Florence is heading toward a deeper pool of warm water over the southwestern Atlantic, a significant phase of intensification is likely to begin by tonight, continuing through Tuesday or Wednesday. In fact, the official intensity forecast explicitly shows rapid intensification occurring between 24 and 48 hours from now, and Florence is expected to become a major hurricane by Monday. The HFIP Corrected Consensus (HCCA) and the Florida State Superensemble (FSSE), both of which tend to do well in these scenarios, are both near the upper end of the guidance suite, especially through day 3. Even by days 4 and 5, the HWRF, HMON, and ICON intensity consensus are near the top end of the guidance, close to HCCA and FSSE. Given the signals in the environment, and the solutions provided by these models, the NHC intensity forecast shows Florence reaching category 4 intensity by day 3 and maintains that through the end of the forecast period.Hurricane Florence Wind Speeds Sept 8 to Sept 18 2018

Florence’s longer-term motion is 265/6 kt. The cyclone appears to be slowing down as was expected, and this type of motion is likely to continue for the next 24-36 hours. In fact, the track guidance has slowed down during this period, and the updated NHC track forecast is a little slower than the previous one. After 36 hours, the most notable change in the models was a northeastward shift in the 06Z GFS. However, that run appears to be an outlier from the rest of the dynamical models, and its trend opposes the slight westward shift noted in the HCCA and FSSE aids. The updated NHC track forecast is therefore very close to or slightly west of the previous forecast on days 4 and 5. The exact path of Florence as it approaches the southeastern U.S. coastline will depend heavily on the position and strength of the blocking high pressure that is expected to develop north of Bermuda and extend westward over the eastern U.S., and so far there has not been much more clarity on those important details.

Key Messages:

1. Florence is forecast to be a dangerous major hurricane near the southeast U.S. coast by late next week, and the risk of direct impacts continues to increase. However, given the uncertainty in track and intensity forecasts at those time ranges, it’s too soon to determine the exact timing, location, and magnitude of those impacts.

2. Interests along the U.S. East Coast, particularly from north Florida through North Carolina, should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials.

3. Large swells are affecting Bermuda and will begin to affect portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 24.5N  54.3W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 12H  09/0000Z 24.6N  55.0W   60 KT  70 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 24H  09/1200Z 24.6N  56.1W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 36H  10/0000Z 24.8N  57.5W   85 KT 100 MPH - Category 2 (ENE North Palmetto Point, Bahamas)
 48H  10/1200Z 25.1N  59.3W  100 KT 115 MPH - Category 3 (ENE North Palmetto Point, Bahamas)
 72H  11/1200Z 26.3N  64.9W  115 KT 130 MPH - Category 4 (ENE North Palmetto Point, Bahamas)
 96H  12/1200Z 28.5N  71.5W  125 KT 145 MPH - Category 4 (E Cocoa Beach, Florida)
120H  13/1200Z 31.5N  77.0W  120 KT 140 MPH - Category 4 (ESE Savannah, Georgia)

NWS National Hurricane Center Miami FL 500 AM AST Sat Sep 08 2018

Although Florence remains a sheared tropical cyclone, satellite imagery during the past 6 h also indicates that the shear has started to abate somewhat, which has allowed the dense cirrus canopy to build back over the previously exposed low-level circulation center. Furthermore, deep convection with overshooting cloud tops near -80C and an abundance of lightning activity have developed very close to the center. Based on these data along with Dvorak intensity estimates of T3.5/55 kt from TAFB and SAB, the initial intensity has been raised to 55 kt.

The initial motion estimate is 265/8 kt. The mid-latitude flow across CONUS and the northern Atlantic is forecast to flatten out and become more zonal over the next 48 h or so, resulting in the development of a narrow east-west oriented ridge along 35/36N latitude. This large-scale feature is expected to steer Florence in a general westward direction during that time. By days 3-5, however, the flow across the central and western U.S. is forecast to buckle and become more meridional as a deep mid-/upper-level trough over the northeast Pacific pushes inland over the western U.S., causing downstream ridging over the northeastern U.S. and northwestern Atlantic. The global models agree on this general change in the synoptic-scale flow pattern, but they differ noticeably on where a downstream mid-/upper-level high pressure cell takes up residence over the Atlantic either to the northwest or northeast of Bermuda. The farther west/east the high develops will determine how far west/east Florence will eventually move and possibly affect the U.S. east coast beyond the 5-day forecast period. The new official forecast track is close to the previous advisory track through 48 h, and then was nudged a little to the left or west of the previous track, which is close to the consensus model TVCN and is north of the corrected-consensus models FSSE and HCCA since the bulk of the NHC model guidance lies north of those latter two models.

The upper-level environment is expected to improve to significantly during the next 12 h and beyond with the current 20 kt of southwesterly shear forecast to give way to shear of less than 10 kt. By 72 h and beyond, light shear from the southeast and east along with the development of strong upper-level outflow jets to the north of Florence is expected to create an environment that favors significant and possibly even rapid strengthening. The new NHC intensity forecast has been increased over the previous advisory in anticipation of these very favorable dynamical conditions developing, and now shows Florence becoming a hurricane by Sunday and a major hurricane in 3 days, followed by additional strengthening over the very warm Atlantic waters of at least 29 deg C that are about 2 deg C above normal right now. The consensus models IVCN and HCCA were closely followed, which are a little below the FSSE model.

Key Messages:

1. Regardless of Florence’s eventual track, large swells are affecting Bermuda and will begin to affect portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents.

2. The risk of other direct impacts associated with Florence along the U.S. East Coast next week has increased. However, there is still very large uncertainty in model forecasts of Florence’s track beyond day 5, making it too soon to determine the exact location, magnitude, and timing of these impacts. Interests near and along the U.S. East Coast should monitor the progress of Florence through the weekend and ensure they have their hurricane plans in place.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 24.5N  54.2W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 12H  08/1800Z 24.6N  55.0W   60 KT  70 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 24H  09/0600Z 24.6N  56.0W   65 KT  75 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 36H  09/1800Z 24.6N  57.2W   75 KT  85 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 48H  10/0600Z 24.9N  59.0W   90 KT 105 MPH - Category 2 (ENE San Juan, Puerto Rico)
 72H  11/0600Z 26.0N  64.0W  105 KT 120 MPH - Category 3 (ENE Coopers Town, Bahamas )
 96H  12/0600Z 28.0N  70.2W  120 KT 140 MPH - Category 4 (ENE West Palm Beach, Florida)
120H  13/0600Z 30.9N  75.8W  125 KT 145 MPH - Category 4 (ENE Jacksonville, Florida)

NWS National Hurricane Center Miami FL 500 PM AST Fri Sep 07 2018

Little has changed with Florence’s  structure during the day. The low-level center is located on the southwestern side of the deep convection due to moderate to strong southwesterly shear, and satellite intensity estimates are essentially the same from this morning. Therefore, the estimated maximum winds remain 55 kt. NOAA is scheduled to conduct a research mission with the P-3 aircraft tomorrow, which should provide some useful wind data and give us a better handle on the cyclone’s intensity.

Vertical shear is still expected to gradually decrease over the next day or two, likely reaching values of 10 kt or less by 48 hours. During this period, Florence should become more vertically stacked, which would allow for some reintensification, possibly back to hurricane strength within 36-48 hours. After 48 hours, the shear is expected to remain generally low, and oceanic heat content values will increase significantly as Florence moves over the waters between Bermuda and the northern Leeward Islands. This is a classic recipe for a quick intensification trend, and Florence is expected to become a major hurricane by days 4 and 5. The generally skillful HCCA, Florida State Superensemble, and ICON intensity consensus are all near 110-115 kt by day 5, and because of this, no notable changes were required from the previous official intensity forecast.

Florence has been moving south of due west (260 degrees) at 7 kt, located south of a low- to mid-level ridge. The cyclone is expected to continue moving generally westward for the next 48 hours while it remains sheared. As Florence begins to strengthen and become vertically stacked after 48 hours, it should begin to turn west-northwestward, steered by a deeper flow regime. By days 4 and 5, an exceptionally strong blocking ridge is forecast to develop between Bermuda and the Northeast U.S., keeping Florence on a west-northwestward trajectory with an increase in forward speed by the end of the forecast period. A slight southwestward adjustment was made to the NHC forecast to account for Florence’s initial motion and a slight shift in the overall guidance envelope. For most of the forecast period, the official forecast is close to a blend of the GFS and ECMWF.

Key Messages:

1. Regardless of Florence’s eventual track, large swells are affecting Bermuda and will begin to affect portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents.

2. The risk of other direct impacts associated with Florence along the U.S. East Coast next week has increased. However, there is still very large uncertainty in model forecasts of Florence’s track beyond day 5, making it too soon to determine the exact location, magnitude, and timing of these impacts. Interests near and along the U.S. East Coast should monitor the progress of Florence through the weekend and ensure they have their hurricane plans in place.

FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 24.8N  52.5W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 12H  08/0600Z 24.6N  53.5W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 24H  08/1800Z 24.6N  54.7W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 36H  09/0600Z 24.6N  55.8W   60 KT  70 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 48H  09/1800Z 24.8N  57.0W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 72H  10/1800Z 25.8N  60.9W   90 KT 105 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 96H  11/1800Z 27.5N  67.0W  110 KT 125 MPH - Category 3 (E Coopers Town, Bahamas)
120H  12/1800Z 30.5N  73.0W  115 KT 130 MPH - Category 4 (E Jacksonville, Florida)

NWS National Hurricane Center Miami FL 1100 AM AST Fri Sep 07 2018

Moderate to strong southwesterly shear continues to affect Florence  , but visible and microwave satellite images indicate that the cyclone is maintaining a vigorous, but tilted, circulation. A mid-level eye feature is noted in both types of satellite imagery, but the low-level center still appears displaced to the southwest. Subjective and objective satellite intensity estimates have stopped falling–and some have even begun to increase a bit again–so the initial intensity is being held at 55 kt.

The shear over Florence has likely reached its maximum and is expected to decrease below 20 kt in 6-12 hours and then decrease to 10 kt or less in 36 hours. All the while, sea surface temperatures will be gradually increasing to between 28-29C, and perhaps more importantly, oceanic heat content values will double in 3-4 days. It may take the cyclone some time to gather itself once the shear abates, but once it becomes vertically stacked again, the intensity is likely to increase significantly. The guidance is in agreement on this scenario, and Florence is likely to re-attain hurricane status in about 48 hours and then potentially major hurricane strength by days 4-5. The new official forecast is fairly similar to the previous one, generally close to the ICON intensity consensus and slightly below the HCCA model on days 4 and 5.

Florence is moving westward, or 270/7 kt, to the south of the eastern periphery of a subtropical ridge extending east of the Mid-Atlantic United States. The global model guidance is actually in fairly good agreement on the general evolution of the steering pattern around Florence through day 5. While it remains a tilted cyclone, Florence is expected to continue moving westward for the next 48 hours. After that time, a break in the ridge should allow Florence to turn west-northwestward over the southwestern Atlantic. A new mid-level ridge is expected to develop over the western Atlantic on days 4-5, but the position of that high will play a big role regarding how much Florence may turn by the end of the forecast period. Only a slight southward nudge of forecast track was required on this cycle, keeping the NHC prediction between the GFS and ECMWF solutions.

Hurricane Florence Projected Wind Speeds Sep 7 to Sep 12 2018
Hurricane Florence Projected Wind Speeds Sep 7 to Sep 12 2018

Key Messages:

1. Regardless of Florence’s eventual track, large swells will begin to affect Bermuda later today and portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents.

2. The risk of other direct impacts associated with Florence along the U.S. East Coast next week has increased. However, there is still very large uncertainty in model forecasts of Florence’s track beyond day 5, making it too soon to determine the exact location, magnitude, and timing of these impacts. Interests near and along the U.S. East Coast should monitor the progress of Florence through the weekend and ensure they have their hurricane plans in place.

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 25.0N  51.8W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 12H  08/0000Z 24.9N  52.8W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 24H  08/1200Z 24.9N  54.0W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 36H  09/0000Z 24.9N  55.1W   60 KT  70 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 48H  09/1200Z 25.1N  56.2W   65 KT  75 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 72H  10/1200Z 25.9N  59.8W   90 KT 105 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 96H  11/1200Z 27.5N  65.5W  110 KT 125 MPH - Category 3 (ESE Tucker's Town, Bermuda)
120H  12/1200Z 30.0N  72.0W  115 KT 130 MPH - Category 4 (ESE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 500 PM AST Thu Sep 06 2018

Vertical shear has taken its toll on Florence today as evidenced by a continued degradation of the overall cloud pattern. The circulation appears tilted, with the low-level center partially exposed to the southwest of the deep convection. Subjective and objective Dvorak Current Intensity (CI) numbers have fallen, and a blend of the various estimates supports an initial intensity of 70 kt.

The intensity forecast is relatively straightforward in the short-term as shear is expected to remain strong, which should continue Florence’s weakening trend, potentially taking the system below hurricane strength. By 24 hours, vertical shear is forecast to decrease, and the SSTs gradually warm along the forecast track. Assuming the overall circulation remains intact, Florence shouldn’t have any problems restrengthening beginning in a day or so. In fact, guidance suggests that Florence could once again become a major hurricane in 4 or 5 days. The new NHC intensity forecast is essentially an update of the previous one, and is only adjusted to account for recent trends. Largely, the official forecast is close to the various consensus aids.

Hurricane Florence Projected Wind Speeds Sep 6 to Sep 11 2018
Hurricane Florence Projected Wind Speeds Sep 6 to Sep 11 2018

Owing to the degraded structure and tilted nature of the system, Florence has wobbled a bit to the west, but the longer-term motion estimate is 305/09. Low- to mid-level ridging should cause Florence to turn toward the west-northwest and west between 12-48 hours while the cyclone recovers from the strong shear. Thereafter, Florence is anticipated to become a deep cyclone again, but an even stronger ridge should maintain the west-northwestward motion, at a faster speed, through day 5. The ridge is forecast to be sufficiently strong such that some track models show a motion just south of due west during the next 12-36 hours. Beyond day 3, the track forecast becomes increasingly uncertain due to differing evolutions of the steering pattern over the western Atlantic. While all of the global models show a progressive trough eroding the ridge, they differ in the strength of the trough and the ridge to the north of Florida. These differences result in a great deal of bifurcation in the track guidance, especially among global model ensemble members, at the end of the forecast period. In such situations, prudence suggests a reliance on continuity, and the the new official NHC track forecast is shifted only slightly south towards the TVCN multi-model consensus and HCCA. It is important to note that deterministic track models in these types of situations often display considerable run-to-run changes, and the uncertainty in this forecast remains larger than normal.

Key Messages:

1. Regardless of Florence’s eventual track, large swells will begin to affect Bermuda on Friday and portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents.

2. There is still very large uncertainty in Florence’s track beyond day 5, and it is too soon to determine what, if any, other impacts Florence could have on the U.S. East Coast next week.

3. Since we are near the peak of hurricane season, this is a good time for everyone who lives in a hurricane-prone area to ensure they have their hurricane plan in place.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 25.0N  49.6W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 12H  07/0600Z 25.4N  50.7W   60 KT  70 MPH - Tropical Storm  (ESE Tucker's Town, Bermuda)
 24H  07/1800Z 25.5N  52.1W   65 KT  75 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 36H  08/0600Z 25.5N  53.4W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 48H  08/1800Z 25.6N  54.6W   75 KT  85 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 72H  09/1800Z 26.4N  57.1W   90 KT 105 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 96H  10/1800Z 28.0N  61.0W  100 KT 115 MPH - Category 3 (ESE Tucker's Town, Bermuda)
120H  11/1800Z 30.0N  67.0W  105 KT 120 MPH - Category 3 (E Jacksonville, Florida)

NWS National Hurricane Center Miami FL  1100 AM AST Thu Sep 06 2018

Vertical shear has increased since yesterday, which has caused a degradation of Florence’s   structure and a decrease in its maximum winds. The cloud-filled eye has been eroded over the past hour or so, and the deep convection is no longer symmetric, with the low-level circulation peeking out from under the higher clouds. Dvorak CI numbers from TAFB and SAB have fallen to T5.0-5.5 (90-100 kt), while the objective numbers from UW-CIMSS support 70-90 kt.

The initial intensity is set at 90 kt, near the middle of this wide range of estimates. The intensity forecast has been somewhat of a self-defeating prophecy due to the nuances of the environmental shear. Even though Florence was able to rapidly intensify yesterday in an area just south of a zone of strong shear, the hurricane’s stronger-than- expected intensity caused it to move more poleward, into that stronger shear. Right now, shear analyses range anywhere from 25-30 kt, and the latest available guidance suggests that this level of shear should continue for another 12-24 hours. As a result, continued weakening is forecast over the next day or so. After 36 hours, Florence is likely to encounter an upper-level environment that is more conducive for reintensification. The NHC forecast is adjusted downward toward the newest consensus aids, especially during the first 48 hours, but it still shows Florence reaching major hurricane strength again by days 4 and 5.

Florence’s forward motion has slowed just a little to 9 kt toward the northwest (315 degrees). A mid-level ridge is building to the north, which is likely to cause the hurricane to turn westward by 36 hours, with that motion continuing through about day 3. After that time, there is still considerable uncertainty in the evolution of the steering pattern over the western Atlantic, especially on day 4. On one hand, the GFS and HWRF dig a strong shortwave trough over Atlantic Canada by Monday, creating a break in the ridge which would allow Florence to turn northwestward. On the other hand, the ECMWF and UKMET both have weaker troughs and maintain stronger ridging over the northwestern Atlantic, allowing Florence to maintain a westward or west-northwestward course. All the models show a mid-level high over the western Atlantic by Tuesday. Due to typical biases among these models in the part of the Atlantic, we prefer to be between the GFS and ECMWF solutions at this time, which places the official NHC track forecast close to the TVCN multi-model consensus and just north of HCCA. There is still considerable model ensemble spread for Florence’s track beyond day 5. Given the large uncertainty at these time ranges, it is far too soon to speculate what, if any, impacts Florence may have on the U.S. East Coast next week. Regardless of Florence’s eventual track, large swells emanating from the hurricane will reach Bermuda beginning on Friday and portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 24.6N  48.6W   90 KT 105 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 12H  07/0000Z 25.2N  49.8W   80 KT  90 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 24H  07/1200Z 25.6N  51.3W   75 KT  85 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 36H  08/0000Z 25.6N  52.6W   75 KT  85 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 48H  08/1200Z 25.7N  54.0W   80 KT  90 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 72H  09/1200Z 26.3N  56.4W   90 KT 105 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 96H  10/1200Z 28.0N  59.5W  100 KT 115 MPH - Category 3 (ESE Tucker's Town, Bermuda)
120H  11/1200Z 29.5N  65.0W  105 KT 120 MPH - Category 3 (ESE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 500 AM AST Thu Sep 06 2018

Southwesterly shear continues to affect Florence. Since the last advisory, the cloud pattern has become more asymmetric, and cloud tops surrounding the ragged eye have warmed. AMSR imagery around 0430 UTC indicated that the hurricane’s eye is tilted slightly southwest to northeast with height, but the low- to mid-level inner-core was mostly intact. Based on an average of Final-T and CI numbers from TAFB and SAB, the initial intensity has been lowered to 100 kt, and objective estimates are even lower.

Given the wind shear and current appearance of Florence, additional weakening in the short-term seems likely, and all of the intensity guidance agrees. From 24-72 h, the spread increases with the statistical models generally showing continued gradual weakening for another day or two, while the dynamical models show little change or slight restrengthening. By day 5, all of the guidance calls for Florence to restrengthen. The guidance envelope and consensus is lower with this model cycle, but the NHC intensity forecast has only been adjusted slightly lower, mainly in the first 72 h of the forecast. The official forecast is now a little above the IVCN intensity consensus and HCCA at most forecast hours, generally favoring the stronger solution of the dynamical models.

Florence has continued to track northwestward, and the initial motion is 315/10 kt. The cyclone is still forecast to gradually turn westward over the next 48 h, in response to a building mid-level ridge to its north. Beyond that time, a mid-latitude trough over the northwestern Atlantic could create enough of a weakness in the ridge to steer the hurricane farther north, closer to Bermuda, as shown by the latest GFS. However, the ECMWF and UKMET suggest that the ridge will not be significantly affected, and Florence will move more westward. The ensembles from the GFS and ECMWF do not clearly favor one solution over another, and in fact many members track Florence somewhere in-between. While little change was made to the previous forecast and the new official track forecast remains close to the various consensus aids, the model spread has increased and confidence in the forecast is low.

There is still considerable model ensemble spread for Florence’s track beyond day 5. Given the large uncertainty at these time ranges, it is far too soon to speculate what, if any, impacts Florence may have on the U.S. East Coast next week. Regardless of Florence’s eventual track, large swells emanating from the hurricane will reach Bermuda beginning on Friday and portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT  06/0900Z 24.1N  47.9W  100 KT 115 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 12H  06/1800Z 24.8N  49.1W   90 KT 105 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 24H  07/0600Z 25.4N  50.8W   90 KT 105 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 36H  07/1800Z 25.6N  52.2W   90 KT 105 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 48H  08/0600Z 25.6N  53.6W   90 KT 105 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 72H  09/0600Z 26.1N  56.1W   95 KT 110 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 96H  10/0600Z 27.2N  59.0W  105 KT 120 MPH - Category 3 (ESE Tucker's Town, Bermuda)
120H  11/0600Z 29.0N  63.5W  110 KT 125 MPH - Category 3 (ESE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 1100 AM AST Wed Sep 05 2018

Remarkably, Florence  has continued to strengthen. The hurricane has a compact central dense overcast with cold cloud tops completely encircling a clear, well-defined eye. With the improved structure, subjective Dvorak estimates have increased to T5.5/102 kt from TAFB and T6.0/115 kt from SAB, while the latest objective UW-CIMSS ADT estimate is T5.8/110 kt. The initial intensity is therefore set at 110 kt as a blend of these numbers, with Florence having become a major hurricane earlier this morning.

Given the estimated maximum winds, Florence has been rapidly intensifying since yesterday, an event that was not foreseen by any intensity models, nor forecasters. Diagnostics from the SHIPS model and UW-CIMSS shear analyses have been consistently showing southwesterly shear of 20-25 kt in the vicinity of Florence, but it is possible that those schemes are averaging over a larger area than might be reasonable given the hurricane’s small size. Florence has apparently been able to find a small pocket of relatively low shear, and with waters becoming progressively warmer, the hurricane has strengthened significantly more than anticipated. This makes the intensity forecast incredibly uncertain. SHIPS actually shows the shear increasing over the next 24 hours, but global model fields suggest that the hurricane may still be able to continue within the protected pocket of lower shear for the next several days. As a result, the NHC official forecast keeps Florence’s intensity well above the available guidance, which all show the hurricane weakening over the next day or two. The new NHC prediction follows this trend and also shows some weakening, but this is a low-confidence forecast. Either way, Florence is expected to remain a hurricane throughout the 5-day period.

The track forecast also has its challenges. The initial motion estimate is northwestward, or 305/11 kt. It now appears that stronger upper-level ridging may take shape to the north of Florence over the next few days, forcing the hurricane to turn back toward the west-northwest from 36-72 hours. After 72 hours, a break in the ridge should allow Florence to turn back toward the northwest, but the bulk of the track models have trended westward since yesterday. In light of these trends, the NHC official track forecast has been shifted westward on days 4 and 5, but not quite as far as the various model consensus aids. It is worth stressing that there is still a significant amount of spread among the GFS and ECMWF ensemble members by the end of the forecast period, and just like the intensity forecast, the track forecast is of low confidence.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 22.0N  45.7W  110 KT 125 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 12H  06/0000Z 22.7N  47.2W  110 KT 125 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 24H  06/1200Z 23.8N  49.0W  100 KT 115 MPH - Category 3 (ESE Tucker's Town, Bermuda)
 36H  07/0000Z 24.7N  50.6W   95 KT 110 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 48H  07/1200Z 25.1N  52.1W   90 KT 105 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 72H  08/1200Z 25.7N  54.7W   90 KT 105 MPH - Category 2 (ESE Tucker's Town, Bermuda)
 96H  09/1200Z 27.0N  57.0W   95 KT 110 MPH - Category 2 (ESE Tucker's Town, Bermuda)
120H  10/1200Z 28.5N  59.0W   95 KT 110 MPH - Category 2 (ESE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 1100 PM AST Tue Sep 04 2018

GOES-16 imagery shows that the eye of Florence  has become better defined during the last several hours, with even some mesovortices in the eye present on the shortwave infrared channel. Satellite intensity estimates continue to rise, and the initial wind speed is set to 85 kt, just below the latest TAFB estimate of 90 kt.

Florence remains on a west-northwestward course at 300/10 kt. This general course is expected to continue through 36 or 48 hours while the hurricane remains near the southwestern edge of the subtropical ridge. After that time, the forecast becomes more uncertain, depending on the presence of a narrow mid-level ridge over the north-central Atlantic Ocean. A look at the ensemble guidance shows a bifurcation developing by day 5, with the ECMWF favoring a more northward turn, and the UKMET ensembles showing a stronger ridge and a continuation of a west-northwest track. The new NHC forecast is adjusted westward at long range, in line with the corrected-consensus aids, but don’t be surprised if this forecast undergoes some large changes in the next few cycles, given the split in the guidance.

This intensity forecast is also difficult. Florence certainly has exceeded expectations during the last day or so, with the hurricane on the verge of rapidly intensifying during the last 24 hours despite a marginal environment. Some more strengthening is called for in the short term to reflect the current trend. However, the global models continue to insist that southwesterly shear will increase over the next couple of days which, in combination with considerable dry air aloft, should cause some weakening. Later tomorrow, a slow weakening trend should begin and continue through 48 hours, although not weakening as much as shown in the past advisory. This can’t be considered a high-confidence prediction in light of what Florence has done so far. On Friday, an upper-level low could cut off to the south of the cyclone, which would lessen the shear near Florence, and the hurricane should be moving over steadily increasing SSTs. Restrengthening is forecast at long range, and it wouldn’t be surprising if the new NHC prediction turns out to be too low. It is best to be conservative, however, since the track uncertainty is increasing by the end of the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 20.7N  43.9W   85 KT 100 MPH - Category 2 (WNW Mindelo, Cape Verde)
 12H  05/1200Z 21.5N  45.5W   90 KT 105 MPH - Category 2 (ENE British Virgin Islands)
 24H  06/0000Z 22.6N  47.6W   80 KT  90 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 36H  06/1200Z 23.7N  49.4W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 48H  07/0000Z 24.7N  50.9W   65 KT  75 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 72H  08/0000Z 26.0N  53.5W   65 KT  75 MPH - Category 1 (ESE Tucker's Town, Bermuda)
 96H  09/0000Z 27.3N  55.8W   70 KT  80 MPH - Category 1 (ESE Tucker's Town, Bermuda)
120H  10/0000Z 29.0N  57.5W   80 KT  90 MPH - Category 1 (ESE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 1100 AM AST Tue Sep 04 2018

Florence’s  structure has gradually increased in organization, with SSMIS passes from a few hours ago revealing the development of a mid-level microwave eye. Dvorak estimates have responded in kind–TAFB is up to T4.0, SAB is at T4.5, and the objective ADT is in between at T4.4. Since there still appears to be moderate southwesterly shear inducing some tilt to the cyclone and disrupting the infrared satellite pattern, the initial intensity is raised conservatively to 65 kt, making Florence a hurricane.

The current motion remains west-northwestward, or 295/10 kt, with Florence positioned near the southwestern edge of the subtropical ridge. The steering pattern ahead of Florence is rather complicated and will be evolving over the next few days. A large and complex mid-/upper-level trough located northeast of the Leeward Islands is expected to give way to the development of two upper-level highs centered near the Greater Antilles and southwest of the Azores, with Florence slowing down and turning northwestward between these new features.

Despite this complex pattern, the spread in the track models is less than normal, which increases the confidence in the NHC track forecast for the next 5 days. There is some spread which begins to develop around day 5, with the ECMWF model moving Florence a little faster toward the north while the GFS maintains a slower speed and keeps the system to the south. The updated NHC track forecast has been nudged slightly to the east of the previous forecast on days 4 and 5, close to the TVCX consensus but not as far as the HCCA and ECMWF models. There is still too much model spread after day 5 to speculate what Florence might do beyond the official forecast period. Despite Florence becoming a hurricane, the southwesterly shear affecting the cyclone is expected to increase over the next day or two, which should prevent further intensification. In fact, the increasing shear, as well as mid-level relative humidities below 50 percent, should cause weakening between 24 and 72 hours. After 72 hours, decreasing shear and warmer sea surface temperatures should foster some re-intensification, with Florence expected to reattain hurricane intensity by day 5. The intensity guidance is in good agreement, and the NHC forecast is very close to a blend of HCCA, the Florida State Superensemble, and the ICON consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 19.7N  42.5W   65 KT  75 MPH - Category 1 (WNW Mindelo, Cape Verde)
 12H  05/0000Z 20.3N  44.0W   65 KT  75 MPH - Category 1 (ENE British Virgin Islands)
 24H  05/1200Z 21.3N  46.2W   65 KT  75 MPH - Category 1 (ESE Turks and Caicos)
 36H  06/0000Z 22.4N  48.2W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 48H  06/1200Z 23.6N  50.0W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 72H  07/1200Z 25.6N  52.7W   50 KT  60 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 96H  08/1200Z 27.5N  55.0W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
120H  09/1200Z 29.5N  56.5W   65 KT  75 MPH - Category 1 (ESE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 1100 PM AST Mon Sep 03 2018

Although Florence  continues to produce a fairly circular area of deep convection, microwave images have revealed that there is a significant southwest-to-northeast vertical tilt of the circulation due to southwesterly shear. The initial intensity is held at 60 kt, using a blend of the Dvorak CI-numbers from TAFB and SAB. This estimate is a little below the latest automated Dvorak values from CIMSS at the University of Wisconsin.

The strong tropical storm is moving west-northwestward, or 285 degrees, at 12 kt steered by a subtropical ridge to its north. The storm is expected to gradually turn northwestward with a decrease in forward speed during the next several days as it moves toward a persistent weakness in the subtropical ridge. There remains a fair amount of spread in the guidance, especially in the 3- to 5-day time period, but the consensus aids have changed little this cycle. Therefore, no significant changes were made to the previous forecast, and this one lies near the middle of the guidance envelope.

Little change in strength is expected through early Tuesday as Florence remains over marginally warm waters and in moderate wind shear conditions. Slight weakening is expected during the middle part of the week due to a gradual increase in southwesterly or westerly shear. Beyond that time, however, the shear is expected to decrease and Florence will be over much warmer waters. Therefore, slow strengthening is shown at the end of the forecast period. This forecast is unchanged from the previous one, and is in good agreement with the HCCA guidance.

The 34- and 50-kt initial wind radii have been expanded outward based on recent ASCAT passes.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 18.9N  41.0W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 12H  04/1200Z 19.4N  42.7W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 24H  05/0000Z 20.1N  44.9W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 36H  05/1200Z 21.1N  47.2W   55 KT  65 MPH - Tropical Storm (ESE Antigua and Barbuda)
 48H  06/0000Z 22.1N  49.5W   50 KT  60 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 72H  07/0000Z 24.5N  53.1W   50 KT  60 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
 96H  08/0000Z 26.8N  55.8W   55 KT  65 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)
120H  09/0000Z 28.4N  57.8W   60 KT  70 MPH - Tropical Storm (ESE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 500 PM AST Mon Sep 03 2018

Florence  appears a little better organized than earlier today. Deep convection is slightly stronger near and to the north of the center, and the cloud pattern still resembles a central dense overcast. A blend of the latest Dvorak classifications suggests a slightly higher wind speed, and accordingly, the initial intensity is nudged upward to 60 kt.

The strong tropical storm is moving westward, or 280 degrees, at 13 kt steered by a subtropical ridge to its north. The global models all show a persistent weakness in the subtropical ridge during the next several days due to a series of troughs moving across the Atlantic. In response, Florence is expected to gradually turn northwestward with a slight reduction in forward speed during the next several days. While there remains a fair amount of spread in the models from 72 to 120 h, there has been a notable trend to the right, or north, during the past few model cycles. The official track forecast is adjusted slightly to the right as well, trending toward the latest consensus aids.

Little change in strength is expected through tonight as Florence remains over marginally warm waters and in moderate wind shear conditions. However, nearly all of the intensity models show a slow weakening trend during the next few days. This weakening is in response to a gradual increase in southwesterly or westerly shear. Beyond a few days, however, the shear is expected to decrease and Florence will be over much warmer waters. Therefore, slow strengthening is shown in the 3 to 5 day period. This forecast is slightly higher than the previous one at the longer range, but is otherwise unchanged.

FORECAST POSITIONS AND MAX WINDS

INIT  03/2100Z 18.6N  39.8W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 12H  04/0600Z 19.0N  41.6W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 24H  04/1800Z 19.6N  43.9W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 36H  05/0600Z 20.4N  46.1W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 48H  05/1800Z 21.5N  48.4W   50 KT  60 MPH - Tropical Storm (SE Tucker's Town, Bermuda)
 72H  06/1800Z 23.7N  52.5W   50 KT  60 MPH - Tropical Storm (SE Tucker's Town, Bermuda)
 96H  07/1800Z 26.0N  55.3W   55 KT  65 MPH - Tropical Storm (SE Tucker's Town, Bermuda)
120H  08/1800Z 28.0N  57.5W   60 KT  70 MPH - Tropical Storm (SE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 1100 AM AST Mon Sep 03 2018

While Florence’s structure improved overnight, the cloud tops have warmed and the deep convection has thinned during the past several hours. The 12Z satellite intensity estimates range from 55 to 65 kt, but given recent trends the initial intensity is set at the low end of that range at 55 kt, although this is quite uncertain given the recent fluctuations in the cloud pattern.

UW-CIMSS satellite diagnostics indicate that around 20 kt of southwesterly shear is affecting Florence, while the SHIPS analysis based on the GFS fields shows only about 10 kt. SSTs warm from this point forward along the forecast track, but shear is expected to be steady or strengthen, and the mid-level relative humidity values decrease to around 50 percent during the next 48 to 72 hours. Given these mixed factors, the NHC intensity forecast shows some possibility for strengthening in the next 12 hours, followed by a slow decay through 72 hours. Some restrengthening is forecast late in the period as SSTs warm above 28C and the atmospheric moisture increases. The NHC forecast is close to or a bit above the latest IVCN consensus aid and about 5 kt above the previous NHC forecast through 96 hours.

The initial motion estimate is 285/14. Florence will be steered generally west-northwestward for the next 72 hours by the Atlantic subtropical ridge, followed by a northwestward turn at days 4 and 5. While there is large spread in the guidance between the HWRF on the right and the UKMET on the left, the GFS, ECMWF, and their ensemble means are more tightly clustered near the middle of the guidance envelope. Since the overall track forecast reasoning has not changed, the new NHC forecast remains near the middle of the guidance. This forecast is a bit north of the previous NHC track given the initial position and lies a little south of the consensus aids to reflect less influence of the outlier HWRF model to the north.

FORECAST POSITIONS AND MAX WINDS

INIT  03/1500Z 18.3N  38.7W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 12H  04/0000Z 18.6N  40.7W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 24H  04/1200Z 19.1N  43.0W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 36H  05/0000Z 19.9N  45.3W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 48H  05/1200Z 20.8N  47.6W   50 KT  60 MPH - Tropical Storm (SSE Tucker's Town, Bermuda)
 72H  06/1200Z 23.0N  52.2W   45 KT  50 MPH - Tropical Storm (SSE Tucker's Town, Bermuda)
 96H  07/1200Z 25.0N  55.0W   50 KT  60 MPH - Tropical Storm (SSE Tucker's Town, Bermuda)
120H  08/1200Z 27.0N  58.0W   55 KT  65 MPH - Tropical Storm (SSE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 500 AM AST Mon Sep 03 2018

The structure of Florence  has recovered overnight. Several recent microwave images indicate that the tropical storm’s center is still dislocated to the south of most of the associated convection, but convective banding has increased. There is also evidence that Florence has developed better defined low-level inner-core. Satellite intensity estimates have increased and now range from 45 to 60 kt. As a compromise of the various estimates, the initial intensity has been raised slightly to 50 kt, but its worth noting that this increase is within the noise level of our ability to observe the intensity of tropical storms over the open ocean.

Based on SHIPS diagnostics, the southwesterly shear affecting Florence could remain moderate for the next 12 h, and some slight intensification is possible. However, by 24 h, an increase in the shear should kick off a gradual weakening trend. By the end of the forecast period, the tropical storm is forecast to re-intensify while it moves over warmer SSTs and the environmental shear decreases. Given the improved current structure of Florence, the new official intensity forecast shows slight intensification for the first 12 h. Beyond that time, the models are in good agreement and the NHC forecast is near the middle of the relatively tight intensity guidance envelope.

The tropical storm is still moving west-northwestward, at an estimated 14 kt. A continued west to west-northwest motion is forecast by all the global models for the next couple of days. By the end of the forecast period, nearly all of the guidance shows a turn toward the northwest, and the main source of uncertainty in the track forecast continues to be exactly when and to what extent Florence will make this turn. At this point I have no reason to depart from the various consensus models, and the track forecast is very close to the previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 18.0N  37.5W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 12H  03/1800Z 18.3N  39.6W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 24H  04/0600Z 18.7N  42.0W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 36H  04/1800Z 19.3N  44.2W   45 KT  50 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 48H  05/0600Z 20.0N  46.5W   45 KT  50 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 72H  06/0600Z 22.2N  51.1W   40 KT  45 MPH - Tropical Storm (SSE Tucker's Town, Bermuda)
 96H  07/0600Z 24.5N  54.5W   45 KT  50 MPH - Tropical Storm (SSE Tucker's Town, Bermuda)
120H  08/0600Z 26.0N  57.0W   55 KT  65 MPH - Tropical Storm (SSE Tucker's Town, Bermuda)

NWS National Hurricane Center Miami FL 500 AM AST Sun Sep 02 2018

Florence continues to gradually strengthen. Microwave imagery from a recent AMSR overpass indicates that a majority of the deep convection is located in the northern semicircle of the tropical storm, but its center is still well embedded within the central dense overcast. A blend of satellite intensity estimates from SAB and TAFB supports increasing the intensity to 50 kt.

Some additional slight strengthening is still expected over the next day or so while Florence remains in a light shear environment and over marginal SSTs. Beginning in about 3 days, slow weakening is forecast due to an expected increase in wind shear associated with an extensive mid- to upper-level trough over the central Atlantic. The intensity guidance is in generally good agreement through 120 h, and the official forecast remains near the intensity consensus.

The initial motion is now 290/13. The track guidance is fairly tightly packed for the first 48 h or so, with the spread increasing more quickly beyond that time. For the next couple of days, the subtropical ridge should keep Florence moving westward to west-northwestward at a similar forward speed. By day 3, a west-northwest to northwest motion is forecast to begin, as the aforementioned mid- to upper-level trough influences the track of the tropical storm. While all of the global models show this general scenario, the extent to which Florence will gain latitude is less certain. A stronger Florence will likely turn more toward the northwest, while a weaker, shallower system should continue on a more westward to west-northwestward track. For now, the NHC forecast remains near the middle of the guidance envelope, close to all of the consensus models. This track is also generally in line with the official intensity forecast, which shows a somewhat weaker system than the GFS (on the north side of the guidance), but a stronger one than the ECMWF (on the south side).

FORECAST POSITIONS AND MAX WINDS

INIT  02/0900Z 16.5N  31.4W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 12H  02/1800Z 17.0N  33.5W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 24H  03/0600Z 17.5N  36.3W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 36H  03/1800Z 18.0N  39.0W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 48H  04/0600Z 18.5N  41.4W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 72H  05/0600Z 20.1N  45.5W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 96H  06/0600Z 22.0N  49.5W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
120H  07/0600Z 24.0N  53.0W   45 KT  50 MPH - Tropical Storm (ESE Tucker's Town , Bermuda)

NWS National Hurricane Center Miami FL 500 PM AST Sat Sep 01 2018

Tropical Storm Florence – The cloud pattern has continued to improve with a circular area of convection near the center, and a cyclonically curved band surrounding the system. The upper-level outflow is fair in all quadrants. Although the cloud pattern is better organized, the Dvorak T-numbers have not changed, and only support 40 kt at this time.

Florence has a couple of more days embedded within a low-shear environment which supports strengthening, but it is also currently heading toward marginal SSTs. By the time the cyclone reaches warmer waters again, the shear is forecast to be unfavorable. The best option at this time is to show only a very modest strengthening at the rate indicated by the intensity consensus aids.

Florence has been moving toward the west-northwest or 285 degrees at 12 to 14 kt. No change in track is anticipated during the next 3 days while Florence is located to the south of the Atlantic subtropical ridge. After that time, Florence will reach a break in the ridge causing the cyclone to turn toward the northwest with a decrease in forward speed. The latter portion of the forecast is uncertain since the strength of the subtropical ridge to the north has been fluctuating from run to run in each model. At this time, the overall guidance has been shifting a little bit westward, suggesting a stronger ridge. On this basis, the NHC forecast was adjusted slightly in that direction at the end of the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  01/2100Z 15.6N  29.0W   40 KT  45 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 12H  02/0600Z 16.2N  31.0W   45 KT  50 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 24H  02/1800Z 16.8N  33.7W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 36H  03/0600Z 17.5N  36.5W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 48H  03/1800Z 18.0N  39.0W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 72H  04/1800Z 19.5N  43.5W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 96H  05/1800Z 21.5N  48.0W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
120H  06/1800Z 23.5N  52.0W   50 KT  60 MPH - Tropical Storm (E Arthur's Town, Bahamas)

NWS National Hurricane Center Miami FL 1100 AM AST Sat Sep 01 2018

Satellite images indicate that Florence’s   cloud pattern has improved in organization with the low-level center embedded within the convection, and a cyclonically curved band surrounding the system. A blend of subjective and objective Dvorak numbers from TAFB, SAB, and the UW-CIMMS yield an initial intensity of 40 kt.

My predecessor wrote a very clear explanation of the reasoning of his track and intensity forecasts, and I do not think I can improve on it. The environment continues to be mixed with favorable and unfavorable conditions for Florence to strengthen. Currently, the shear is low and favors strengthening, but the ocean along the cyclone’s forecast path is cooler. The latter condition should inhibit significant intensification. After 3 days, the opposite is anticipated — the ocean will be warmer, but the shear will likely be high. Only at the very long range could both factors become favorable. The best option at this time is to show only a gradual strengthening at the rate indicated by the intensity consensus aids.

Florence is still moving toward the west-northwest or 295 degrees at 12 kt. No change in track is anticipated during the next 3 days while Florence is located to the south of the subtropical ridge. After that time, Florence will reach a break in the ridge causing the cyclone to turn toward the northwest with a decrease in forward speed. The confidence in the forecast is high during the next 3 days when the track guidance envelope is tightly packed. Thereafter, the confidence is not so high since the envelope widens and becomes bounded by the easternmost HWRF and the westernmost ECMWF models. Since the guidance envelope shifted a little bit westward, the NHC forecast was also adjusted slightly in that direction, primarily during the end of the forecast period.

FORECAST POSITIONS AND MAX WINDS

INIT  01/1500Z 14.8N  27.8W   40 KT  45 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 12H  02/0000Z 15.3N  29.7W   45 KT  50 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 24H  02/1200Z 16.1N  32.4W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 36H  03/0000Z 16.5N  35.0W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 48H  03/1200Z 17.0N  37.5W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 72H  04/1200Z 19.0N  42.5W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 96H  05/1200Z 21.0N  46.5W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
120H  06/1200Z 23.5N  50.0W   55 KT  65 MPH - Tropical Storm (E Arthur's Town, Bahamas)

NWS National Hurricane Center Miami FL 500 AM AST Sat Sep 01 2018

Tropical Storm Florence – A recent SSMIS microwave pass has revealed that the cyclone has become much better organized with more pronounced convective banding. Satellite intensity estimates are wide ranging, spanning from T1.5/25 kt from SAB to T3.4/53 kt from the UW-CIMSS ADT. Since the numbers overall have increased, and the structure has improved, the initial intensity is raised to 35 kt, in closest agreement to the TAFB estimate, but this could be conservative. This makes the depression Tropical Storm Florence, the sixth named storm of the season.

Florence is moving west-northwestward, or 285/12 kt, and should maintain this motion for the next 48 hours while traveling along the southern periphery of the subtropical ridge. After 48 hours, the storm is expected to reach a break in the ridge, causing it to slow down and turn northwestward by day 5. The biggest change noted among the track models on this cycle was a westward shift in the overall guidance envelope. The European model, in particular, swung significantly to the left, showing a weaker Florence not feeling the break in the ridge quite as much. I’d like to see this trend continue before making a significant change to the forecast, so for now the updated NHC track prediction is only nudged westward. That said, the models appear to be trending away from a definitive recurvature scenario.

The environment is mixed with positives and negatives for Florence’s strengthening. For the first 3 days, vertical shear over Florence should be quite low, but the cyclone will also be moving through a less-than-ideal thermodynamic environment with marginal sea surface temperatures and decreasing mid-level moisture. After 3 days, the thermodynamic environment should begin to improve, but then the shear is forecast to strengthen. These conflicting signals point to only gradual strengthening, and the suite of intensity models aren’t too far off from one another, nor from the previous NHC forecast. For that reason, no significant changes were made in this forecast package.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 14.5N  26.7W   35 KT  40 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 12H  01/1800Z 15.0N  28.7W   40 KT  45 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 24H  02/0600Z 15.7N  31.2W   45 KT  50 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 36H  02/1800Z 16.4N  33.7W   50 KT  60 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 48H  03/0600Z 17.1N  36.3W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 72H  04/0600Z 18.7N  41.4W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
 96H  05/0600Z 21.0N  45.5W   60 KT  70 MPH - Tropical Storm (ENE Mindelo, Cape Verde)
120H  06/0600Z 23.5N  48.5W   55 KT  65 MPH - Tropical Storm (ENE Mindelo, Cape Verde)

NWS National Hurricane Center Miami FL 800 PM AST Fri Aug 31 2018

DISCUSSION AND OUTLOOK

At 800 PM AST (0000 UTC), the center of Tropical Depression Six was located near latitude 14.0 North, longitude 25.0 West. The depression is moving toward the west near 15 mph (24 km/h), and this track with a gradual turn to the west-northwest is expected for the next two or three days. On the forecast track, the depression will be passing just south of the Cabo Verde Islands tonight and Saturday morning. The depression should then be moving over the open eastern Atlantic on Sunday and Monday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Strengthening is forecast, and the depression is expected to become a tropical storm tonight or Saturday.

The estimated minimum central pressure is 1004 mb (29.65 inches).

NWS National Hurricane Center Miami FL 500 PM AST Fri Aug 31 2018

High resolution satellite images reveal that the disturbance has developed a well-defined circulation with a cyclonically curved convective band near the center, and plenty of showers in the southern semicircle. The surface pressure in the Cabo Verde Island of Santiago dropped to 1005 mb at 1800 UTC as the cyclone passed to its south. In addition, Dvorak numbers are gradually increasing, and now support classifying the system as a tropical depression.

The depression is becoming better organized, and it will most likely reach tropical storm status in the next several hours. The environmental conditions are favorable for some strengthening during the next 2 to 3 days while the shear is low. Later in the forecast period, the shear is expected to increase, and the SSTs will become marginal halting the strengthing process. The models, primarily the HWRF, are a little less aggressive with the intensity, so the NHC forecast is adjusted slightly downward.

Now that the center has formed, we have a better estimate of the initial motion, which is toward the west or 270 degrees at 13 kt. The depression is gradually becoming steered by the flow around the subtropical ridge, and consequently it has increased its forward speed. This prevailing flow pattern should keep the cyclone on a general west to west-northwest track for the next 2 to 3 days. After that time, a weakness in the ridge will induce a more northwestward to north-northwestward track over the open Atlantic Ocean. The track guidance is very consistent with this solution mainly for the next 3 days. Thereafter, the confidence in the track forecast decreases as the guidance envelope widens and becomes bounded by the westernmost ECMWF and the easternmost HWFI. The NHC forecast continues to be in the middle of the envelope and is very close to the corrected consensus HCCA, which has had great skill so far this year.

FORECAST POSITIONS AND MAX WINDS

INIT  31/2100Z 13.8N  24.7W   30 KT  35 MPH - Tropical Storm (WSW Praia,Cape Verde)
 12H  01/0600Z 14.3N  26.7W   35 KT  40 MPH - Tropical Storm (WSW Praia,Cape Verde)
 24H  01/1800Z 14.9N  29.2W   40 KT  45 MPH - Tropical Storm (WSW Praia,Cape Verde)
 36H  02/0600Z 15.8N  31.8W   45 KT  50 MPH - Tropical Storm (WSW Praia,Cape Verde)
 48H  02/1800Z 16.5N  34.5W   50 KT  60 MPH - Tropical Storm (WSW Mindelo,Cape Verde)
 72H  03/1800Z 18.0N  39.5W   55 KT  65 MPH - Tropical Storm (WSW Mindelo,Cape Verde)
 96H  04/1800Z 20.0N  44.0W   60 KT  70 MPH - Tropical Storm (WSW Mindelo,Cape Verde)
120H  05/1800Z 23.0N  48.0W   55 KT  65 MPH - Tropical Storm (WSW Mindelo,Cape Verde)

NWS National Hurricane Center Miami FL 200 PM AST Fri Aug 31 2018

DISCUSSION AND OUTLOOK

At 200 PM AST (1800 UTC), the disturbance was centered near latitude 13.8 North, longitude 23.3 West. The system is moving toward the west-northwest near 13 mph (20 km/h), and this motion with a slight increase in forward speed is expected to continue for the next three to four days. On the forecast track, the disturbance is expected to continue moving near or over the southern Cabo Verde Islands as a tropical storm later today and tonight. Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Strengthening is forecast during the next several days, and the disturbance is expected to become a tropical storm later today or Saturday.

Environmental conditions are favorable for the system to become a tropical cyclone later today or tonight.

*Formation chance through 48 hours… high…90 percent * Formation chance through 5 days…high…90 percent

NWS National Hurricane Center Miami FL 1100 AM AST Fri Aug 31 2018

The circulation is better defined this morning,  but the associated convection is rather weak. In fact, Dvorak numbers have not changed overall, and do not support classifying the system as a tropical cyclone yet. It seems like both NHC and the global models predicted the development of a cyclone too soon. Nevertheless, the environmental conditions are favorable for both genesis and strengthening, and a tropical depression or a storm is expected to form later today or Saturday. The shear does not appear to be a problem at this time, but the cyclone should be moving over marginal SSTs, limiting the amount of intensification. The HWRF model changed its tune to a more reasonable one, and it now shows more modest strengthening. The NHC forecast is similar to the previous one, and continues to be very close to the intensity consensus.

The disturbance is moving toward the west-northwest or 285 degrees at about 11 kt. The subtropical high should continue to steer the system toward the west-northwest with some increase in forward speed for the next 2 to 3 days. After that time, a weakness in the ridge will induce a more northwestward track over the open Atlantic Ocean. This is supported by the track guidance which continues to be in very good agreement for the next 3 days. Thereafter, the guidance envelope widens and becomes bounded by the westernmost ECMWF and the easternmost GFS models decreasing the confidence in the track forecast.

Tropical Storm Florence Wind Probability 1100 Hours August 31 2018
Tropical Storm Florence Wind Probability 1100 Hours August 31 2018
FORECAST POSITIONS AND MAX WINDS

INIT  31/1500Z 13.7N  22.7W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 12H  01/0000Z 14.1N  24.5W   35 KT  40 MPH - Tropical Storm (WSW Praia,Cape Verde)
 24H  01/1200Z 14.8N  27.0W   40 KT  45 MPH - Tropical Storm (WSW Praia,Cape Verde)
 36H  02/0000Z 15.5N  29.5W   45 KT  50 MPH - Tropical Storm (ESE Nova Sintra,Cape Verde)
 48H  02/1200Z 16.2N  32.1W   50 KT  60 MPH - Tropical Storm (WSW Mindelo,Cape Verde)
 72H  03/1200Z 17.5N  37.5W   55 KT  65 MPH - Tropical Storm (WSW Mindelo,Cape Verde)
 96H  04/1200Z 19.5N  42.0W   60 KT  70 MPH - Tropical Storm (WSW Mindelo,Cape Verde)
120H  05/1200Z 22.0N  45.5W   65 KT  75 MPH - Category 1 (WSW Anegada, British Virgin Islands)

NWS National Hurricane Center Miami FL 800 AM AST Fri Aug 31 2018

DISCUSSION AND OUTLOOK

At 800 AM AST (1200 UTC), the disturbance was centered near latitude 13.7 North, longitude 21.8 West. The system is moving toward the west-northwest near 12 mph (19 km/h), and this motion at a slightly faster forward speed is expected to continue for the next three to four days. On the forecast track, disturbance is expected to move near or over the southern Cabo Verde Islands as a tropical storm later today and tonight.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Strengthening is forecast during the next several days, and the disturbance is expected to become a tropical storm later today or Saturday.

Environmental conditions are favorable for the system to become a tropical cyclone later today. * Formation chance through 48 hours… high…90 percent * Formation chance through 5 days…high...90 percent

NWS National Hurricane Center Miami FL 500 AM AST Fri Aug 31 2018

Even though the circulation is gradually becoming less elongated , there is still relatively little deep convection near the estimated center of circulation. Instead, most of the convection remains confined to the monsoon trough southwest of the center, where low-level convergence is strongest. Therefore, the system is not quite yet being designated as a tropical cyclone.

Global model fields suggest that the low should detach from the monsoon trough within the next 12 hours, which would likely allow deep convection to form closer to the center. Assuming that happens, the system is also forecast to strengthen and become a tropical storm by this afternoon while it approaches the southern Cabo Verde Islands. Although vertical shear is expected to be relatively light for much of the forecast period, sea surface temperatures ahead of the system are marginal, and the low will likely move over a minimum of oceanic heat content in 48-72 hours. Adding on top of that a drier mid-level environment, only gradual strengthening is anticipated through day 5. A majority of the intensity models agree on this scenario, with the exception of the HWRF model, which brings the system close to major hurricane strength at the end of the forecast period. Since that solution is discounted at the moment, the NHC intensity forecast is below the HCCA guidance and closest to the intensity consensus.

The low appears to have turned west-northwestward with an initial motion of 285/10 kt. A mid-level high centered west of the Canary Islands should continue to steer the disturbance west-northwestward at a faster clip for the next 4 days or so. By the end of the forecast period, a weakness in the ridge over the eastern Atlantic could cause the system to turn northwestward. The new NHC track forecast is a little slower than the previous one during the first 72 hours and then a little to the west on days 4 and 5 to better match the latest guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  31/0900Z 13.6N  21.4W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 12H  31/1800Z 14.2N  23.1W   35 KT  40 MPH...TROPICAL STORM
 24H  01/0600Z 14.8N  25.6W   40 KT  45 MPH - Tropical Storm (WSW Praia, Cape Verde)
 36H  01/1800Z 15.5N  28.3W   45 KT  50 MPH - Tropical Storm (ESE Nova Sintra, Cape Verde)
 48H  02/0600Z 16.2N  30.9W   50 KT  60 MPH - Tropical Storm (WSW Mindelo, Cape Verde)
 72H  03/0600Z 17.4N  36.2W   55 KT  65 MPH - Tropical Storm (WNW Mindelo, Cape Verde)
 96H  04/0600Z 19.0N  41.0W   60 KT  70 MPH - Tropical Storm (WNW Mindelo, Cape Verde)
120H  05/0600Z 21.5N  45.0W   65 KT  75 MPH - Tropical Storm (WNW Mindelo, Cape Verde)

NWS National Hurricane Center Miami FL 200 AM EDT Fri Aug 31 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Potential Tropical Cyclone Six, located a couple of hundred miles east- southeast of the Cabo Verde Islands.
* Formation chance through 48 hours…high…90 percent.
* Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Thu Aug 30 2018

Tropical Storm Florence

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Potential Tropical Cyclone Six, located southeast of the Cabo Verde Islands. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 AM AST Thu Aug 30 2018

The area of low pressure that moved off the coast of Africa has continued to become better organized, and is producing a large area of disturbed weather with gusty winds, but currently lacks a well-defined center. Environmental conditions are favorable for additional development, and a tropical depression or a tropical storm could form an any time today or Friday. Given the high chances that this system could bring tropical storm conditions to a portion of the southern Cabo Verde Islands, advisories have been initiated on Potential Tropical Cyclone Six. Most of the intensity guidance calls for strengthening and so does the NHC forecast.

The system is embedded within the easterly trades and this flow pattern will steer the disturbance toward the west or west- northwest during the next few days. By the end of the forecast period, a turn toward the northwest should begin as the system reaches a weakness in the subtropical high. This is consistent with the output of the global models.

FORECAST POSITIONS AND MAX WINDS

INIT  30/1500Z 12.9N  18.4W   25 KT  30 MPH...POTENTIAL TROP CYCLONE
 12H  31/0000Z 13.2N  20.1W   30 KT  35 MPH...TROPICAL DEPRESSION
 24H  31/1200Z 13.5N  22.0W   35 KT  40 MPH - Tropical Storm (ESE Praia, Cape Verde)
 36H  01/0000Z 14.0N  24.0W   45 KT  50 MPH - Tropical Storm (WSW Praia, Cape Verde)
 48H  01/1200Z 15.0N  27.0W   55 KT  65 MPH - Tropical Storm (ESE Nova Sintra, Cape Verde)
 72H  02/1200Z 16.5N  33.0W   65 KT  75 MPH - Category 1 (WSW Mindelo, Cape Verde)
 96H  03/1200Z 18.5N  38.0W   65 KT  75 MPH - Category 1 (WNW Mindelo, Cape Verde)
120H  04/1200Z 20.0N  42.0W   65 KT  75 MPH - Category 1 (WSW Antigua and Barbuda)

NWS National Hurricane Center Miami FL 800 AM EDT Thu Aug 30 2018

Correction to remove blank line For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

Satellite images and surface observations indicate that a well-defined low pressure system is located just off the west coast of Senegal, Africa. Environmental conditions are favorable for a tropical depression or a tropical storm to form as the disturbance moves westward or west-northwestward at about 15 mph near the Cabo Verde Islands during the next day or two. This system is expected to bring heavy rains and strong gusty winds to the Cabo Verde Islands on Friday and Saturday, and if the current development trend continues, Tropical Storm Watches or Warnings will likely be required for these islands later today. Interests on the Cabo Verde Islands should continue to closely monitor the progress of this developing disturbance. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…90 percent.

A vigorous low pressure area associated with a tropical wave is forecast to form between the coast of Africa and the Cabo Verde Islands on Thursday. Conditions appears to be favorable for development, and a tropical depression could form over the weekend while the system moves west-northwestward near the Cabo Verde Islands and the adjacent Atlantic. This system is expected to bring rains and gusty winds to those islands in two or three days, and interests in that region should monitor the progress of this disturbance. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…medium…60 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Wed Aug 29 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

1. A low pressure area is forecast to form between the coast of Africa and the Cabo Verde Islands in association with a tropical wave that is expected to move off the west coast of Africa late Thursday or early Friday. Additional development is anticipated, and a tropical depression could form over the weekend while the system moves west-northwestward near the Cabo Verde Islands. Interests in those islands should monitor the progress of this system. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium…50 percent.

If this system forms it will be Tropical Storm Florence.

NWS National Hurricane Center Miami FL 200 PM EDT Tue Aug 28 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico: 1. A tropical wave is forecast to move off the west coast of Africa on Thursday. Some development of this system is possible over the weekend while it moves westward across the eastern tropical Atlantic Ocean.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...20 percent.

 NWS National Hurricane Center Miami FL 800 AM EDT Tue Aug 28 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

1. A tropical wave is forecast to move off the west coast of Africa on Thursday. Some development of this system is possible over the weekend while it moves westward across the eastern tropical Atlantic Ocean.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

Article Resources:

Recent Tropical Storms

Please follow and like us: