Tropical Storm Irma

Hurricane Irma Track 1100 Hours September 9 2017
Hurricane Irma Track 1100 Hours September 9 2017
Hurricane Irma Satellite 1300 Hours September 9 2017
Hurricane Irma Satellite 1300 Hours September 9 2017

NWS National Hurricane Center Miami FL 100 PM EDT Sat Sep 09 2017

…100 PM EDT POSITION UPDATE…
…IRMA MOVING NEAR THE NORTH COAST OF CUBA …

Earlier today there was a report from a weather station in Ciego
de Avila, Cuba, of a wind gust to 159 mph (256 km/h).

SUMMARY OF 100 PM EDT…1700 UTC…INFORMATION
———————————————-
LOCATION…23.0N 80.0 W
ABOUT 75 MI…125 KM E of Varadero Cuba
ABOUT 160 MI…255 KM SE of Key West, Florida
MAXIMUM SUSTAINED WINDS…125 MPH…205 KM/H
PRESENT MOVEMENT…W OR 280 DEGREES AT 9 MPH…15 KM/H
MINIMUM CENTRAL PRESSURE…941 MB…27.79 INCHES

Previous Warning 1100 AM EDT Sat Sep 09 2017

…IRMA CONTINUES TO POUND THE NORTH COAST OF CUBA…
…FORECAST TO RESTRENGTHEN WHILE HEADING FOR SOUTH FLORIDA AND THE
KEYS…

SUMMARY OF 1100 AM EDT…1500 UTC…INFORMATION
———————————————–
LOCATION…22.8N 79.8W
ABOUT 90 MI…145 KM ESE OF VARADERO CUBA
ABOUT 175 MI…285 KM SE OF KEY WEST FLORIDA
MAXIMUM SUSTAINED WINDS…125 MPH…205 KM/H
PRESENT MOVEMENT…W OR 280 DEGREES AT 9 MPH…15 KM/H
MINIMUM CENTRAL PRESSURE…941 MB…27.79 INCHES

Previous Warning 500 AM EDT Sat Sep 09 2017

The eye of Irma has been moving over the islands along the north coast of Cuba, and satellite imagery along with preliminary data from an Air Force Reserve Hurricane Hunter aircraft indicates that the hurricane has weakened. The initial intensity is reduced to 135 kt, and this may be generous.

The initial motion is now 285/10. Irma is moving along the southwestern side of the subtropical ridge, which is about to weaken due to a mid- to upper-level trough moving into the southeastern United States. The track guidance is in good agreement that Irma should continue west-northwestward for the next
12-24 h, followed by a turn toward the north-northwest that would take the center parallel to the west coast of the Florida peninsula. Later in the forecast period, the cyclone should turn northwestward and eventually stall as it interacts with the aforementioned trough. The track guidance has changed onlyslightly since the previous advisory. Thus the new forecast track follows the previous forecast in calling for Irma to move along the coast of Cuba, then over the Lower Florida Keys, and then over and near the Florida West coast. It should be noted that because of the hurricane’s angle of approach to the west coast of Florida, it is extremely difficult to pinpoint exactly where the center might move onshore.

There is an opportunity for Irma to re-intensity as it crosses the warm waters of the Florida Straits. However, the large-scale models forecast significant westerly shear developing at about 24 h, and it is unclear how much strengthening could occur before  then. The first part of the intensity forecast thus calls for little change in strength through 36 h, and Irma is still expected to be a dangerous hurricane as it approaches the Florida Keys and the west coast of Florida. After that time, movement over land and strong shear should cause steady weakening, with Irma eventually decaying to a remnant low by the end of the forecast period.

KEY MESSAGES:

1. Irma will continue to bring life-threatening wind, storm surge, and rainfall hazards to portions of the Bahamas and the north coast of Cuba, especially over the adjacent Cuban Keys, through tonight.

2. Irma is expected to make landfall in Florida as an extremely dangerous major hurricane, and will bring life-threatening wind impacts to much of the state regardless of the exact track of the center.

3. There is the danger of life-threatening storm surge inundation in portions of central and southern Florida, including the Florida Keys, during the next 36 hours, where a Storm Surge Warning is in effect. The threat of significant storm surge flooding along the southwest coast of Florida has increased, and 8 to 12 feet of inundation above ground level is possible in this area. This is a life-threatening situation. Everyone in these areas should take all actions to protect life and property from rising water and follow evacuation instructions from local officials.

4. Irma is expected to produce very heavy rain and inland flooding. Total rain accumulations of 8 to 15 inches, with isolated amounts of 20 inches are expected over the Florida Keys and much of the Florida peninsula through Tuesday night. Irma will likely bring periods of heavy rain to much of the Florida Panhandle, Georgia, South Carolina, and western North Carolina early next week, including some mountainous areas which are more prone to flash flooding. All areas seeing heavy rainfall from Irma will experience a risk of flooding and flash flooding.

FORECAST POSITIONS AND MAX WINDS

INIT 09/0900Z 22.5N 78.8W 135 KT 155 MPH Category 4 (Cayo Santa Maria, Cuba)
12H 09/1800Z 22.9N 80.0W 130 KT 150 MPH Category 4 (Isabella de Sagua, Cuba)
24H 10/0600Z 23.8N 81.1W 130 KT 150 MPH Category 4 (S of Marathon, FL)
36H 10/1800Z 25.4N 81.8W 130 KT 150 MPH Category 4 (SW of Marco Island, FL)
48H 11/0600Z 27.7N 82.4W 105 KT 120 MPH Category 3 (E of Gulf City, FL)
72H 12/0600Z 32.5N 84.5W 45 KT 50 MPH (W of Mauk, GA)
96H 13/0600Z 35.5N 88.0W 25 KT 30 MPH (SW of Decaturville, TN)
120H 14/0600Z 36.0N 87.5W 20 KT 25 MPH (SW of Dickson, TN)

Previous Warning 500 AM EDT Fri Sep 08 2017

Microwave images and data from an Air Force Reserve HurricaneHunter aircraft indicate that Irma is currently undergoing an eyewall replacement cycle. A recent GMI overpass showed an 50 nmiwide outer eyewall, with the inner eyewall weakening. The Hurricane Hunter aircraft reported peak 700-mb winds of 147 kt inthe outer eyewall near 0500 UTC, and maximum SFMR winds were in the 125-130 kt range. Based on these data, the initial intensity isreduced to 135 kt.

Irma is forecast to remain in a favorable warm water, light shear environment for the next 36-48 h. The intensity guidance shows a slow weakening during this time, but Irma is expected to remain at least a Category 4 hurricane until landfall in Florida. After landfall, a fairly quick decay in maximum winds is expected due to land interaction and increased shear, although Irma’s large wind field is likely to still produce hurricane-force winds over a large area. There are two caveats to the intensity forecast. First, some additional weakening could occur during the eyewall replacement, followed by re-intensification as the cycle completes. Second, the ECMWF, UKMET, and NAVGEM forecast a track over or close to the coast of Cuba that is not currently a part of the track forecast. If this occurs, Irma could be weaker than currently forecast along the later parts of the track.

The initial motion is west-northwestward or 285/14. Irma should maintain this general trajectory for the next 24-36 h as it moves along the southwestern side of the subtropical ridge. After that time, the guidance is in good agreement that the ridge should break and allow Irma to turn north-northwestward to northward. There remains some spread between the models on when the turn will occur, with the GFS/Canadian being on the eastern side of the guidance and the UKMET/NAVGEM on the left side. The ECMWF, Florida State Superensemble, and the HFIP Corrected consensus are in the middle of the guidance envelope, and the new track forecast is in bestagreement with those models. Overall, the new forecast track issimilar to the previous forecast, with minor westward adjustments
at 36 and 48 h.

KEY MESSAGES:

1. Irma is an extremely dangerous Category 4 hurricane and will continue to bring life-threatening wind, storm surge, and rainfall hazards to the Turks and Caicos Islands and the Bahamas through Saturday. Heavy rainfall is still possible across portions of Hispaniola through today. Hurricane conditions will also spread over portions of the north coast of Cuba, especially over the adjacent Cuban Keys through Saturday.

2. Severe hurricane conditions are expected over portions of the Florida peninsula and the Florida Keys beginning Saturday night. Irma is likely to make landfall in southern Florida as a dangerous major hurricane, and bring life-threatening storm surge and wind impacts to much of the state. A Hurricane Warning is in effect for southern Florida, the Florida Keys, Lake Okeechobee, and Florida Bay, while Hurricane Watches have been issued northward into central Florida.

3. A Storm Surge Warning is in effect for southern Florida and the Florida Keys. 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. This is a life-threatening situation. Persons located within these areas should take allnecessary 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 has been issued north of the Storm Surge Warning area for portions of the central Florida coast.

4. There is a chance of direct impacts in portions of Georgia, South Carolina, and North Carolina, but it is too early to specify the magnitude and location of these impacts.

FORECAST POSITIONS AND MAX WINDS

INIT 08/0900Z 21.7N 73.8W 155 MPH Category 4  (Turks and Caicos)
12H 08/1800Z 22.1N 75.7W 155 MPH  Category 4  (Turks and Caicos))
24H 09/0600Z 22.6N 77.8W 155 MPH  Category 4  (N of Cayo Romano, Cuba)
36H 09/1800Z 23.3N 79.4W 155 MPH  Category 4  (N of Remedios, Cuba)
48H 10/0600Z 24.5N 80.4W 150 MPH  Category 4 (E of Key West, FL)
72H 11/0600Z 28.0N 81.5W 105 MPH  Category 2  (E of Winterhaven, Fl)
96H 12/0600Z 33.0N 84.0W 45 MPH   (SW of Forsyth , Ga)
120H 13/0600Z 36.0N 87.0W 30 MPH   (Nashville, TN)

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Previous Warning 800 PM EDT Thu Sep 07 2017

…IRMA PUMMELING THE TURKS AND CAICOS ISLANDS…

SUMMARY OF 800 PM EDT…0000 UTC…INFORMATION
———————————————-
LOCATION…21.1N 71.8W
ABOUT 55 MI…85 KM WSW OF GRAND TURK ISLAND
ABOUT 90 MI…145 KM E OF GREAT INAGUA ISLAND
MAXIMUM SUSTAINED WINDS…175 MPH…280 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 16 MPH…26 KM/H
MINIMUM CENTRAL PRESSURE…919 MB…27.14 INCHES

Previous Warning 200 PM AST Thu Sep 07 2017

…EYE OF EXTREMELY DANGEROUS HURRICANE IRMA MOVING BETWEEN
THE NORTH COAST OF HISPANIOLA AND THE TURKS AND CAICOS ISLANDS…

SUMMARY OF 200 PM AST…1800 UTC…INFORMATION

LOCATION…20.7N 70.4W
ABOUT 65 MI…105 KM NNE OF PUERTO PLATA DOMINICAN REPUBLIC
ABOUT 70 MI…115 KM SE OF GRAND TURK ISLAND
MAXIMUM SUSTAINED WINDS…175 MPH…280 KM/H
PRESENT MOVEMENT…WNW OR 290 DEGREES AT 16 MPH…26 KM/H
MINIMUM CENTRAL PRESSURE…922 MB…27.23 INCHES

Previous Warning 500 AM AST Wed Sep 07 2017

Corrected to modify Key Messages to reflect the issuance of a hurricane warning for the northwestern Bahamas.

Irma has become a little less organized during the past few hours. Data from an Air Force reserve Hurricane Hunter aircraft near 0500 UTC indicated that the central pressure had risen to 921 mb and that the winds had decreased both at the 700 mb flight-level and in surface estimates from the Stepped Frequency Microwave Radiometer. Since that time, the eye has become cloud filled and the central convection has become somewhat ragged. The initial intensity is lowered to 155 kt, and this could be a little generous. The next aircraft is scheduled to reach Irma around 1200 UTC.

The initial motion is 290/15. The hurricane is currently being steered by the subtropical ridge to the north, and for the next 48 h or so this motion is expected to continue with a decrease in the forward speed. After 48 h, a mid- to upper-level trough digging into the eastern United States is expected to create a break in the ridge and allow Irma to turn northward. The timing of the turn is the most important question and one still filled with uncertainty. The UKMET, UK Ensemble mean, and the NAVGEM are the models showing the latest turn, and they forecast Irma to move into
the southeastern Gulf of Mexico and near the west coast of the Florida Peninsula. The ECMWF and ECMWF Ensemble mean are in the middle of the model pack and show Irma moving over the southeastern portion of the Florida Peninsula. The GFS, Canadian, and GFS Ensemble mean show the earliest turn and show Irma moving east ofthe coast of Florida toward the southeastern United States. The new forecast track will best follow the ECMWF, as well as the Florida State Superensemble and the HFIP Corrected Consensus, and it calls for the center to move over portions of the southeastern Florida Peninsula between 72-96 h and then across the Atlantic into southern South Carolina by 120 h. Users are again reminded not to
focus on the exact track since the average NHC track errors at days 3, 4, and 5 are about 120, 175, and 225 miles, respectively.

Irma should remain in warm-water, and a low shear environment for about the next three days, and thus is expected to remain a strong hurricane, most likely Category 5 or 4. Fluctuations in intensity are likely during the time due to internal eyewall replacement cycles. The large-scale models suggest that shear could increasestarting at about 72 hr. However, due to the uncertainty as to whether this will happen, the intensity forecast keeps Irma at category 4 strength until landfall in Florida. The 96-120 h points now have a lower intensity due to the forecast of shear and land interaction, but Irma is still expected to be a hurricane when it reaches the southeastern United States.

Since Irma is moving away from Puerto Rico and the radars there, the hourly position estimates are discontinued after this advisory.

FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 20.0N 68.3W 180 MPH Category 5 Hurricane (N of  Dominican Republic)
12H 07/1800Z 20.7N 70.5W 175 MPH Category 5 Hurricane (N of he Dominican Republic)
24H 08/0600Z 21.7N 73.1W 165 MPH Category 5 Hurricane (Turks and Caicos Islands)
36H 08/1800Z 22.3N 75.5W 160 MPH Category 5 Hurricane (Duncan Town Bahamas)
48H 09/0600Z 22.8N 77.4W 155 MPH Category 5 Hurricane (E of Cayo Momano, Cuba)
72H 10/0600Z 24.5N 80.0W 150 MPH Category 4 Hurricane (E of Key West, FL)
96H 11/0600Z 28.5N 80.5W 120 MPH Category 3 Hurricane (NE of Port Camaveral, FL)
120H 12/0600Z 33.0N 81.0W 85 MPH   Category 1 Hurricane (NW of Charleson, SC)

 

Previous Warning 500 PM AST Wed Sep 06 2017

The eye of Irma passed over the northernmost Virgin Islands earlier this afternoon and it is now located just to their northwest. The satellite and radar presentation of the hurricane remains extremely impressive. An Air Force Reserve reconnaissance aircraft reported peak SFMR winds of 156 kt and flight-level winds of 164 kt during its mission this afternoon. Although there have been no SFMR or flight-level winds as high as what was observed yesterday, the initial intensity remains 160 kt, due to the potential of undersampling. Dropsonde observations in the eye indicated that the pressure rose a few millibars this morning, but the most recent aircraft report shows that the pressure has fallen to 914 mb.

The hurricane remains on a west-northwestward motion at about 14 kt. A high pressure ridge over the western Atlantic is forecast to keep Irma on a west-northwestward course over the next 48 to 72hours. The track guidance is still in good agreement during that period, and little change to the NHC forecast was required. By the weekend, a shortwave trough diving southward over the east-central United States is expected to cause Irma to turn northwestward and northward. The 12Z guidance has generally shifted slightly westward, closer to the previous NHC forecast. As a result, little overall change was made to the 4-5 day track forecast. The NHC track is once again close to the HFIP corrected consensus model. This is also near the 12Z GEFS ensemble mean, but a little east of the latest ECMWF ensemble mean. Users are reminded that the average NHC track errors at days 4 and 5 are about 175 and 225 miles, respectively.

Low vertical wind shear and warm waters along the forecast track of Irma should allow it to remain a very powerful hurricane during the next several days, and the intensity forecast is again near the upper-end of the guidance and is the same as the previous advisory through 96 hours. Increasingly southwesterly shear and potential land interaction late in the period is expected to cause some decrease in Irma’s strength by day 5.

Efforts to provide the forecast models with as much data as possible continue, with 6-hourly NWS balloon launches across much of the continental United States, and the NOAA G-IV aircraft currently sampling the environment around the storm.

KEY MESSAGES:

1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to Puerto Rico tonight, the northern coast of Hispaniola Thursday, and the Turks and Caicos and southeastern and central Bahamas Thursday and Friday.

2. Hurricane watches are in effect for the northwestern Bahamas and much of Cuba. Irma is likely to bring dangerous wind, storm surge, and rainfall to portions of these areas on Friday and Saturday.

3. The threat of direct hurricane impacts in Florida over the weekend and early next week has increased. Hurricane watches could be issued for portions of the Florida Keys and the Florida peninsula on Thursday.

FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 18.8N 65.4W 185 MPH  Category 5 Hurricane (NW of San Juan, Puerto, Rico)
12H 07/0600Z 19.6N 67.6W 180 MPH  Category 5 Hurricane (NW of San Juan, Puerto, Rico)
24H 07/1800Z 20.7N 70.4W 175 MPH  Category 5 Hurricane (N of Dominican Republic)
36H 08/0600Z 21.5N 73.1W 165 MPH  Category 5 Hurricane (Turks and Caicos)
48H 08/1800Z 22.2N 75.6W 160 MPH Category 5 Hurricane (N of Santiago de Cuba)
72H 09/1800Z 23.2N 79.0W 155 MPH  Category 5 Hurricane (N of Remedios, Cuba)
96H 10/1800Z 26.0N 80.2W 145 MPH Category 4 Hurricane (SW of Hollywood, Florida)
120H 11/1800Z 31.0N 81.0W 120 MPH Category 3 Hurricane (Jekyll Island, Georgia)

Previous Warning 1200 PM AST Wed Sep 06 2017

…1200 PM AST POSITION UPDATE…
…CORE OF IRMA HEADING TOWARD THE VIRGIN ISLANDS…

The government of the Netherlands has discontinued the Hurricane Warning for Saba and St. Eustatius.

A wind gust to 87 mph (141 km/h) has recently been reported at St. Thomas in the U.S. Virgin Islands.

SUMMARY OF 1200 PM AST…1600 UTC…INFORMATION
———————————————-
LOCATION…18.3N 64.2W
ABOUT 55 MI…85 KM E OF ST. THOMAS
ABOUT 125 MI…200 KM E OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS…185 MPH…295 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 16 MPH…26 KM/H
MINIMUM CENTRAL PRESSURE…922 MB…27.23 INCHES

Previous Warning 1100 AM AST Wed Sep 06 2017

The eye of Irma passed over Barbuda, St. Barthelemy, and St. Martin this morning, and will be moving over portions of the British and U.S. Virgin Islands shortly. A NOAA National Ocean Service observing site on Barbuda measured sustained winds of 103 kt with a gust to 135 kt earlier this morning before the anemometer failed. The station also reported a minimum pressure of 916.1 mb. A minimum pressure of 915.9 mb was reported on St. Barthelemy. An Air Force reconnaissance aircraft that performed a single pass through the eye this morning reported SFMR winds of 152 kt in the northwestern eyewall around 12Z. Assuming there are stronger winds in the northeastern eyewall, the initial intensity remains 160 kt for this advisory. Another Air Force aircraft is currently entering the storm.

Irma is moving west-northwestward or 285/14 kt. A strong highpressure ridge extending from the central Atlantic westward is expected to keep Irma moving west-northwestward during the next 2 to 3 days. The track guidance is in good agreement during this period and the NHC track is along the southern edge of the guidance envelope in best agreement with the ECMWF and HFIP corrected consensus model. After that time, a shortwave trough moving southward over the east-central United States is expected to erode the western portion of the ridge. As a result, Irma is forecast to turn northwestward and northward, but there is still a fair amount of uncertainty regarding the exact timing and location of recurvature. The NHC forecast has been shifted eastward to be in better agreement with the latest model guidance, however it should be noted that there are numerous GEFS and ECMWF ensemble members that take Irma over and/or west of Florida. The updated NHC track is in best agreement with the latest ECMWF ensemble mean. Users are reminded that the average NHC track errors at days 4 and 5 are about 175 and 225 statue miles, respectively.

Irma is forecast to remain within favorable atmospheric conditions and over warm waters during the next 3 to 4 days. Therefore, Irma is likely to remain a very powerful hurricane during this time, and the NHC intensity forecast is unchanged from the previous advisory through day 4. Since the 120-h forecast point is now offshore, the intensity forecast at that time has been adjusted accordingly.

Now that Irma’s eye is clearly visible in radar imagery from San Juan, Tropical Cyclone Updates with hourly position estimates will be issued starting at 1200 PM AST (1600 UTC).

KEY MESSAGES:

1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to portions of the northern Leeward Islands, including the Virgin Islands and Puerto Rico today.

2. A hurricane warning is in effect for the northern coast of the Dominican Republic, the southeastern Bahamas, the Turks and Caicos, and portions of Haiti, with a hurricane watch in effect for the central Bahamas and much of Cuba. Irma is likely to bring dangerous wind, storm surge, and rainfall to some of these areas tonight through Friday.

3. Irma could directly affect the remainder of the Bahamas and Cuba as an extremely dangerous major hurricane later this week. Residents
in these areas should monitor the progress of Irma and listen to advice given by officials.

4. Direct impacts from wind, storm surge, and rainfall are possible in the Florida Keys and portions of the Florida Peninsula beginning later this week and this weekend. However, given the forecast uncertainty at these time ranges, it is too soon to specify the location and magnitude of these impacts.

FORECAST POSITIONS AND MAX WINDS

INIT 06/1500Z 18.2N 64.0W 185 MPH Category 5 Hurricane (SE of  British Virgin Islands)
12H 07/0000Z 19.0N 66.2W 180 MPH Category 5 Hurricane (N of San Juan, Puerto Rico)
24H 07/1200Z 20.2N 69.0W 175 MPH Category 5 Hurricane (N of Dominican Republic )
36H 08/0000Z 21.2N 71.7W 165 MPH Category 5 Hurricane (S of Turks and Caicos)
48H 08/1200Z 21.9N 74.2W 160 MPH Category 5 Hurricane (W of Turks and Caicos)
72H 09/1200Z 22.9N 78.1W 155 MPH Category 4 Hurricane (Cayo Romano, Cuba)
96H 10/1200Z 25.2N 80.0W 145 MPH Category 4 Hurricane (E of Key Largo, Florida)
120H 11/1200Z 29.0N 80.5W 125 MPH Category 3 Hurricane (SE of New Smyrna Beach, Florida

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Previous Warning 800 AM AST Wed Sep 06 2017

EYE OF POTENTIALLY CATASTROPHIC CATEGORY 5 HURRICANE IRMAPASSES OVER ST. MARTIN NORTHERN EYEWALL POUNDING ANGUILLA.

LOCATION…18.1N 63.3W
ABOUT 15 MI…25 KM W OF ST. MARTIN
ABOUT 15 MI…25 KM WSW OF ANGUILLA
MAXIMUM SUSTAINED WINDS…185 MPH…295 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 16 MPH…26 KM/H
MINIMUM CENTRAL PRESSURE…918 MB…27.11 INCHES
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Hurricane Warning is in effect for…
* Antigua, Barbuda, Anguilla, Montserrat, St. Kitts, and Nevis
* Saba, St. Eustatius, and Sint Maarten
* Saint Martin and Saint Barthelemy
* British Virgin Islands
* U.S. Virgin Islands
* Puerto Rico, Vieques, and Culebra
* Dominican Republic from Cabo Engano to the northern border with
Haiti
* Guadeloupe
* Southeastern Bahamas and the Turks and Caicos Islands

Previous Warning 500 AM AST Tue Sep 06 2017

Irma continues as a Category 5 hurricane this morning, having passed over Barbuda a few hours ago. Earlier data from an Air Force Reserve Hurricane Hunter aircraft included SFMR winds near 155 kt and that the central pressure had fallen to 914 mb inside the 25 n mi wide eye. There has been little change in the satellite appearance of the hurricane since that time, so the initial intensity remains 160 kt.

The initial motion is 285/14. Irma is currently being steered by the subtropical ridge to the north, and a general west- northwestward motion on the south side of the ridge is expected during the next 48-72 h. This portion of the forecast track is little changed and is in best overall agreement with the ECMWF model. The forecast has become more uncertain after 72 h due to large eastward shifts by the ECMWF, Canadian, and HWRF models related to forecasts of the mid- to upper-level trough over the southeastern United States. The bulk of the guidance now calls forIrma to turn northward between 78W-80W, moving near or over the Florida east coast or the northwestern Bahamas. The official forecast has also been shifted eastward, but out of respect for the previous forecast and the possibility the guidance may shift back to the west, it lies to the left of the bulk of the guidance. The
forecast now calls for landfall in south Florida between 96-120 h. Users are reminded to not focus on the exact forecast track, especially at the longer ranges, since the average NHC track errors are about 175 and 225 statute miles at days 4 and 5, respectively.

Irma is likely to remain in a light shear, warm water, environment for the next 3 to 4 days. The intensity guidance continues to show slow weakening during this time, and this part of the intensity forecast is little changed from the previous advisory, with Irma remaining a strong hurricane during this time. The intensity forecast is lowered at 120 h due to the forecast landfall, and even if Irma stays over water it is likely to encounter some vertical
shear at that time.

KEY MESSAGES:

1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to portions of the northern Leeward Islands, including the Virgin Islands and Puerto Rico, today. Preparations should be rushed to completion.

2. A Hurricane Warning is in effect for the northern coast of the Dominican Republic, as well as the southeastern Bahamas and the Turks and Caicos, with hurricane watches for portions of Haiti and the central Bahamas. Irma is likely to bring dangerous wind, storm surge, and rainfall to these areas from Wednesday night through Friday.

3. Irma could directly affect the remainder of the Bahamas and Cuba as an extremely dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

4. The chance of direct impacts from Irma beginning later this week and this weekend from wind, storm surge, and rainfall continues to increase in the Florida Keys and portions of the Florida Peninsula. However, it is too soon to specify the timing and magnitude of these impacts.

FORECAST POSITIONS AND MAX WINDS

INIT 06/0900Z 17.9N 62.6W 185 MPH Category 5 Hurricane (S of Anguilla)
12H 06/1800Z 18.6N 64.6W 180 MPH Category 5 Hurricane (S of British Virgin Islands)
24H 07/0600Z 19.6N 67.3W 175 MPH Category 5 Hurricane (NW of San Juan, Puerto Rico)
36H 07/1800Z 20.6N 70.0W 165 MPH Category 5 Hurricane (SE of Turks and Caicos)
48H 08/0600Z 21.3N 72.5W 160 MPH Category 5 Hurricane (S of Turks and Caicos)
72H 09/0600Z 22.5N 77.0W 155 MPH Category 4 Hurricane (NE of Cayo Romano, Cuba)
96H 10/0600Z 24.0N 80.0W 145 MPH Category 4 Hurricane (SE of Key West, Florida
120H 11/0600Z 26.5N 80.9W 120 MPH Category 4 Hurricane (S of Key Clewiston, Florida

Previous Warning 1100 PM AST Tue Sep 05 2017

The satellite view of Irma remains quite spectacular, with an extremely well-defined eye and a large, symmetrical CDO. Reports from NOAA and Air Force Hurricane Hunter aircraft indicate that the central pressure had fallen at about 1 mb per hour since this morning, although very recently the deepening trend has leveled off. Based on SFMR-observed winds from the aircraft, the current intensity remains at 160 kt. The Meteo-France radar imagery suggests a concentric eyewall structure and observations from the aircraft hinted at a secondary wind maximum. If an eyewall replacement becomes more definitive, this would likely halt additional strengthening, and could even lead to some weakening. The official intensity forecast is near or above the model consensus. Given the favorable atmospheric and oceanic environment, Irma is likely to remain a Category 4 or 5 hurricane for the next few days.

Latest center fixes from satellite imagery and the aircraft indicate that Irma is now moving west-northwestward, or 285/13 kt. A strong ridge extending southwestward from the central Atlantic is expected to steer Irma west-northwestward during the next couple of days. A large mid-latitude trough over the eastern United States is forecast to lift northeastward, allowing the ridge to build westward and keep Irma on a westward to west-northwestward heading through Friday. In 4 to 5 days, a small trough diving southward over the east-central U.S. is expected to weaken the western portion of the ridge, causing Irma to turn poleward. Some of the dynamical models have shifted northward a bit from the previous cycle, with the normally reliable GFS looking like a northeast outlier. The official track forecast leans toward the ECMWF solution. Users are reminded to not focus on the exact forecast track, especially at the longer ranges, since the average NHC track errors are about 175 and 225 statute miles at days 4 and 5, respectively.

KEY MESSAGES:

1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to portions of the northern Leeward Islands, including the Virgin Islands and Puerto Rico, on Wednesday. Preparations should be rushed to completion.

2. A Hurricane Warning is in effect for the northern coast of the Dominican Republic, with hurricane watches for Haiti, the southeastern Bahamas and the Turks and Caicos. Irma is likely to bring dangerous wind, storm surge, and rainfall to these areas from Wednesday night through Friday.

3. Irma could directly affect the remainder of the Bahamas and Cuba as an extremely dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

4. The chance of direct impacts from Irma beginning later this week and this weekend from wind, storm surge, and rainfall continues to increase in the Florida Keys and portions of the Florida Peninsula. However, it is too soon to specify the timing and magnitude of these impacts.

FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 17.4N 61.1W 185 MPH Category 5 Hurricane (NE of Antigua and Barbuda)
12H 06/1200Z 18.1N 63.1W 180 MPH Category 5 Hurricane (N of Philipsburg, Sint Maarten)
24H 07/0000Z 19.1N 65.9W 175 MPH Category 5 Hurricane (N of San Juan, Puerto Rico)
36H 07/1200Z 20.1N 68.5W 165 MPH Category 5 Hurricane (N of The Dominican Republic)
48H 08/0000Z 21.0N 71.2W 160 MPH Category 5 Hurricane (S of Turks and Caicos)
72H 09/0000Z 22.0N 76.2W 155 MPH Category 4 Hurricane (NE  of Puerto Padre, Cuba)
96H 10/0000Z 23.2N 79.5W 145 MPH Category 4 Hurricane (N of Remedios, Cuba)
120H 11/0000Z 25.0N 81.5W 140 MPH Category 4 Hurricane (NE of Key West, Florida)

Previous Warning 800 PM AST Tue Sep 05 2017

At 800 PM AST (0000 UTC), the distinct eye of Hurricane Irma was located near latitude 17.2 North, longitude 60.5 West. Irma is moving toward the west near 15 mph (24 km/h). A turn toward the west-northwest is forecast to begin tonight and continue for the next couple of days. On the forecast track, the extremely dangerous core of Irma will move over portions of the northern Leeward Islands
tonight and early Wednesday, move near or over portions of the northern Virgin Islands Wednesday, and pass near or just north of Puerto Rico late Wednesday and Wednesday night.

Maximum sustained winds are near 185 mph (295 km/h) with higher gusts. Irma is an extremely dangerous category 5 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some fluctuations in intensity are likely during the next day or two, but Irma is forecast to remain a powerful category 4 or 5 hurricane during the next couple
of days.

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 minimum central pressure estimated from Hurricane Hunter observations is 916 mb (27.05 inches).

Previous Warning 1100 AM AST Tue Sep 05 2017

Irma is an extremely impressive hurricane in both infrared and visible satellite images. Experimental GOES-16 one-minute visible satellite pictures show a distinct 25-30 n mi wide eye with several mesovortices rotating within with eye. The aircraft have not sampled the northeastern eye wall where the strongest winds were measured shortly before 1200 UTC this morning, but the Air Force plane will be entering the eye in that quadrant momentarily. A peak SFMR wind of 154 kt was reported, with a few others of 149-150 kt. Based on these data the initial intensity is set at 155 kt for this advisory. This makes Irma the strongest hurricane in the Atlantic basin outside of the Caribbean Sea and Gulf of Mexico in the NHC records.

Irma is expected to remain within low vertical wind shear, a moist mid-level atmosphere, and high upper-ocean heat content as it moves west-northwestward during the next several days. These conditions should allow the hurricane to remain very intense throughout much of the forecast period, however, fluctuations in intensity are likely to occur aseyewall replacement cycles take place. The NHC intensity forecast is near the upper-end of the guidance and assumes little overall interaction of Irma with the islands of the Greater Antilles.

Irma continues to move westward at about 12 kt, and a strong subtropical ridge centered over the central Atlantic should steer Irma generally westward today. The ridge is expected to remain in place over the western Atlantic during the next several days and Irma is forecast to move west-northwestward throughout the most of remainder of the forecast period. Around day 5, a shortwave trough dropping southward over the central United States is expected to begin eroding the western portion of the ridge, allowing a Irma to gain some latitude. The new NHC track forecast is close to the HFIP corrected consensus model and is very similar to the previous forecast.

Since Irma is a large hurricane, users are reminded to not focus on the exact forecast track since tropical-storm and hurricane-force winds and life-threatening storm surge extend far from the center. Residents in the Leeward Islands should complete their preparations very soon as the weather will begin to deteriorate over the  easternmost Leeward Islands later this afternoon.

KEY MESSAGES:

1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to portions of the northeastern Leeward Islands beginning later today and the Virgin Islands and Puerto Rico beginning tomorrow. Preparations should be rushed to completion before the arrival oftropical-storm force winds later today in the Leeward Islands and tomorrow morning in Virgin Islands and Puerto Rico.

2. Hurricane watches have been issued for portions of the Dominican Republic and Haiti, the southeastern Bahamas and Turks and Caicos,and Irma could bring dangerous wind, storm surge, and rainfall to those areas on Thursday and Friday.

3. Irma could directly affect the remainder of the Bahamas and Cuba as an extremely dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

4. The chance of direct impacts from Irma later this week and this weekend is increasing in the Florida Keys and portions of the Florida Peninsula. However, it is too soon to specify the timing and magnitude of the impacts. Elsewhere, it is too early to determine what direct impacts Irma might have on the continental United States. Everyone in hurricane-prone areas should ensure that they have their hurricane plan in place.

FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 16.8N 58.4W 180 MPH Category 5 Hurricane (SE of Antigua and Barbuda)
12H 06/0000Z 17.2N 60.3W 180 MPH Category 5 Hurricane (E of Antigua and Barbuda)
24H 06/1200Z 18.1N 63.0W 175 MPH Category 5 Hurricane (Philipsburg, Sint Maarten)
36H 07/0000Z 19.1N 65.9W 165 MPH Category 5 Hurricane (N of San Juan, Puerto Rico)
48H 07/1200Z 20.1N 68.7W 160 MPH Category 5 Hurricane (Punta Cana, Dominican Republic)
72H 08/1200Z 21.4N 74.0W 155 MPH Category 4 Hurricane (NE of Baracoa, Cuba)
96H 09/1200Z 22.7N 78.3W 150 MPH Category 4 Hurricane (N of Cayo Romano, Cuba)
120H 10/1200Z 24.4N 81.2W 145 MPH Category 4 Hurricane (SE of Key West, Florida)

Previous Warning FL 800 AM AST Tue Sep 05 2017

This special advisory is being issued to increase the initial and forecast intensity of Irma.

NOAA and U.S. Air Force Hurricane Hunter aircraft have recently measured peak flight-level winds of around 170 kt and SFMR winds of around 150 kt.

Based on these data the initial intensity has been increased to 150 kt, making Irma an extremely dangerous category 5 hurricane.

Some additional strengthening is still possible, but fluctuations in intensity are likely during the next couple of days due to eye wall replacement cycles.

KEY MESSAGES:

1. Irma is expected to affect the northeastern Leeward Islands as an extremely dangerous category 5 hurricane, accompanied by life-threatening wind, storm surge, and rainfall. Hurricane warnings are in effect for portions of the Leeward Islands. Preparations should be rushed to completion, as tropical-storm force winds are expected to first arrive in the hurricane warning area later today.

2. Irma is also expected to affect the British and U.S. Virgin Islands and Puerto Rico as a dangerous major hurricane beginning tomorrow, with life-threatening wind, storm surge, and rainfall. Hurricane warnings have been issued for these areas, and tropical- storm-force winds are expected to arrive in these areas by early tomorrow.

3. Irma could directly affect Hispaniola, the Turks and Caicos, the Bahamas, and Cuba as an extremely dangerous major hurricane later
this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

4. There is an increasing chance of seeing some impacts from Irma in the Florida Peninsula and the Florida Keys later this week and this weekend. Otherwise, it is still too early to determine what direct impacts Irma might have on the continental United States. However, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place.

FORECAST POSITIONS AND MAX WINDS

INIT 05/1200Z 16.7N 57.7W 175 MPH Category 5 Hurricane (NE of Guadeloupe)
12H 05/1800Z 17.0N 58.9W 180 MPH Category 5 Hurricane (E of Antigua and Barbuda)
24H 06/0600Z 17.7N 61.5W 175 MPH Category 5 Hurricane (E of Barbuda)
36H 06/1800Z 18.6N 64.2W 165 MPH Category 5 Hurricane (E of British Virgin Islands)
48H 07/0600Z 19.6N 67.0W 160 MPH Category 5 Hurricane (N of San Juan, Puerto Rico)
72H 08/0600Z 21.2N 72.5W 155 MPH Category 4 Hurricane (S of Turks and Caicos)
96H 09/0600Z 22.4N 77.2W 155 MPH Category 4 Hurricane (E of Cayo Romano, Cuba)
120H 10/0600Z 24.0N 81.0W 150 MPH Category 4 Hurricane (SE of Key West, Florida)

Previous Warning 800 AM AST Sun Sep 04

NOAA HURRICANE HUNTER AIRCRAFT FINDS IRMA A LITTLE STRONGER.
LOCATION…16.8N 52.6W
ABOUT 610 MI…980 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS…120 MPH…195 KM/H
PRESENT MOVEMENT…WSW OR 255 DEGREES AT 14 MPH…22 KM/H
MINIMUM CENTRAL PRESSURE…947 MB…27.96 INCHES

At 800 AM AST (1200 UTC), the eye of Hurricane Irma was located near latitude 16.8 North, longitude 52.6 West. Irma is moving toward the west-southwest near 14 mph (22 km/h).

A turn toward the west is expected later today, followed by a west-northwestward turn late Tuesday. On the forecast track, the center of Irma will move closer to the Leeward Islands through Tuesday and then be near the northern Leeward Islands Tuesday night.

Data from a NOAA Hurricane Hunter aircraft indicate that the maximum sustained winds have increased to near 120 mph (195 km/h) with higher gusts. Irma is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Additional strengthening is forecast through Tuesday night.

Hurricane-force winds extend outward up to 30 miles (45 km) from the center, and tropical-storm-force winds extend outward up to 140 miles (220 km).

The latest minimum central pressure estimated from data received by the reconnaissance aircraft is 947 mb (27.96 inches).

A Hurricane Watch is in effect for…
* Antigua, Barbuda, Anguilla, Montserrat, St. Kitts, and Nevis
* Saba, St. Eustatius, and Sint Maarten
* Saint Martin and Saint Barthelemy

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.

Interests in the remainder of the Leeward Islands, the British and U.S. Virgin Islands, Puerto Rico, and the Dominican Republic should monitor the progress of Irma. Additional hurricane and tropical storm watches and warnings will likely be required for portions of this area later this morning or this afternoon.

Previous Warning  500 AM AST Sun Sep 04

At 500 AM AST (0900 UTC), the eye of Hurricane Irma was located near latitude 16.9 North, longitude 52.3 West. Irma is moving toward the west-southwest near 14 mph (22 km/h). A turn toward the westis expected later today, followed by a west-northwestward turn late Tuesday. On the forecast track, the center of Irma will move closer to the Leeward Islands through Tuesday and then be near the northern Leeward Islands Tuesday night.

Maximum sustained winds are near 115 mph (185 km/h) with higher gusts. Irma is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some strengthening is forecast through Tuesday night.

Hurricane-force winds extend outward up to 30 miles (45 km) from the center, and tropical-storm-force winds extend outward up to 140 miles (220 km).

The estimated minimum central pressure is 961 mb (28.38 inches).

Previous Warning 200 AM AST Sun Sep 04 2017

Observations from a NOAA Hurricane Hunter aircraft indicated a 25 n mi diameter eye and maximum SFMR-observed surface winds close to 100 kt. That value will be retained for the official intensity. Central core convection is beginning to become a little better organized on satellite imagery and the upper-level outflow is well defined. Given the favorable environment, Irma is likely to strengthen some more over the next day or two. The official intensity forecast follows the model consensus.

Based on center fixes from the Hurricane Hunters, Irma has been moving a little south of west or around 255/12 kt. A strong high pressure ridge over the central Atlantic should steer Irma on a west-southward to westward course over the next couple of days. After that time, a turn toward the west-northwest is likely while Irma nears the western portion of the ridge. There continues to be a rather small cross-track spread in most of the track guidance models, but there are some speed differences. The official track forecast is roughly in the middle of the guidance and is just slightly south of the previous NHC prediction.

Users are reminded to not focus on the exact forecast track since strong winds and heavy rainfall extend well away from the center.

KEY MESSAGES:
1. Irma is expected to affect the northeastern Leeward Islands by the middle of this week as a major hurricane, accompanied by dangerous wind, storm surge, and rainfall impacts, along with rough surf and rip currents. Hurricane watches have been issued for portions of the Leeward Islands and additional hurricane or tropical storm watches or warnings may be required on Monday. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

2. Irma is expected to remain a dangerous major hurricane through the upcoming week and could directly affect the British and U.S. Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos, and the Bahamas. Residents in all of these areas should monitor the progress of Irma and listen to advice given by officials. Tropical storm or hurricane watches could be issued for the British and U.S. Virgin Islands and Puerto Rico on Monday.

3. It is too early to determine what direct impacts Irma might have on the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 04/0300Z 17.2N 51.0W 115 MPH  Category 3 Hurricane (E of Antigua and Barbuda)
12H 04/1200Z 16.7N 52.6W 120 MPH  Category 3 Hurricane (E of Antigua and Barbuda)
24H 05/0000Z 16.5N 54.8W 125 MPH Category 3 Hurricane (E of Antigua and Barbuda)
36H 05/1200Z 16.8N 57.1W 130 MPH  Category 3 Hurricane (E of Antigua and Barbuda)
48H 06/0000Z 17.4N 59.6W 140 MPH  Category 4 Hurricane (E of Antigua and Barbuda)
72H 07/0000Z 19.3N 65.0W 140 MPH  Category 4 Hurricane (N of British Virgin Islands)
96H 08/0000Z 21.2N 70.2W 130 MPH  Category 3 Hurricane (E of Turks and Caicos)
120H 09/0000Z 22.8N 74.5W 130 MPH  Category 3 Hurricane (Bahamas)

Previous Warning 1100 PM AST Sun Sep 03 2017

At 800 PM AST (0000 UTC), the eye of Hurricane Irma was located by a NOAA Hurricane Hunter aircraft near latitude 17.4 North, longitude 50.3 West. Irma is moving toward the west near 14 mph (22 km/h). A westward to west-southwestward motion with some reduction in forward speed is expected through Monday night. On the forecast track, the center of Irma is expected to approach the northern Leeward Islands late Tuesday.

Maximum sustained winds are near 115 mph (185 km/h) with higher gusts. Irma is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some strengthening is forecast during the
next 48 hours Hurricane-force winds extend outward up to 35 miles (55 km) from the center and tropical-storm-force winds extend outward up to 140 miles (220 km). The minimum central pressure estimated from NOAA Hurricane Hunter observations is 959 mb (28.32 inches).

Previous Warning 500 PM AST Sun Sep 03 2017

The satellite presentation of Irma has degraded slightly since this morning with the eye becoming less defined. There is evidence of some northerly flow beneath the cirrus outflow, which may be disrupting the inner core and preventing Irma from strengthening. The latest consensus of the Dvorak satellite estimates suggest that the 100 kt initial intensity could be a little generous, but with a NOAA aircraft headed into the hurricane it is best to wait until data from that mission is received before making any adjustment to the initial wind speed.

Irma has been moving more westward since the previous advisory, but the longer-term motion estimate is still south of due west or 260/12 kt. A strong high pressure ridge over the central Atlantic should steer Irma westward to west-southwestward during the next couple of days. After that time, a turn toward the west-northwest should occur as Irma approaches the western portion of the Atlantic ridge. The cross-track spread of the guidance is still relatively small through day 5, but the ECMWF, UKMET, and HWRF are on the southern side of the guidance envelope, with the GFS near the middle of the envelope. The latest NHC track is once again near the consensus of these typically reliable models, which is between the southern edge of the guidance and the TCVN multi-model consensus. The updated track is not very different from the previous advisory, except at day 5 where it is slightly west of
the previous forecast.

Users are reminded to not focus on the exact forecast track since strong winds and heavy rainfall extend well away from the center. In fact, ASCAT data that arrived after the issuance of the previous advisory indicated that the size of the tropical-storm-force wind field has expanded, especially over the northern semicircle. As a result, the initial and forecast wind radii have been adjusted accordingly.

KEY MESSAGES:
1. Irma is expected to impact the northeastern Leeward Islands by the middle of this week as a major hurricane, accompanied by dangerous wind, storm surge, and rainfall impacts, along with rough surf and rip currents. Hurricane watches have been issued for portions of the Leeward Islands and additional hurricane or tropical storm watches may be required on Monday. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

2. Irma is expected to remain a dangerous major hurricane through the upcoming week and could directly affect the British and U.S. Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos, and the Bahamas. Residents in all of these areas should monitor the progress of Irma and listen to advice given by officials. Tropical storm or hurricane watches could be issued for the British and U.S. Virgin Islands and Puerto Rico on Monday.

3. It is too early to determine what direct impacts Irma might have on the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 03/2100Z 17.6N 49.8W 115 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
12H 04/0600Z 17.2N 51.4W 120 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
24H 04/1800Z 16.8N 53.5W 125 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
36H 05/0600Z 16.8N 55.8W 130 MPH Category 4 Hurricane (NE of Antigua and Barbuda)
48H 05/1800Z 17.3N 58.2W 140 MPH Category 4 Hurricane (NE of Antigua and Barbuda)
72H 06/1800Z 19.1N 63.5W 140 MPH Category 4 Hurricane (NE  British Virgin Islands)
96H 07/1800Z 21.2N 68.8W 130 MPH Category 3 Hurricane (E of Turks and Caicos)
120H 08/1800Z 23.0N 73.5W 130 MPH Category 3 Hurricane (Bahamas)

Previous Warning 1100 AM AST Sun Sep 03 2017

The eye of Irma is a little less distinct in geostationary satellite images this morning, which suggests that the intensity of the hurricane may be fluctuating yet again. However, the initial wind speed is maintained at 100 kt for this advisory, which is close to a consensus of the various objective and subjective satellite intensity estimates. The first reconnaissance mission, a NOAA P-3 Hurricane Hurricane aircraft, is scheduled to depart Barbados for tail Doppler radar mission into Irma late this afternoon and should provide additional information on Irma’s intensity by this evening.

A strong high pressure ridge over the central Atlantic is steering Irma west-southwestward or 255/12 kt. This general motion with some reduction in forward speed is expected during the next day or so. After that time, Irma is forecast to turn westward, then west-northwestward in about 72 hours as it approaches the western portion of the ridge. The various consensus aids are generally a little slower than the previous advisory, but there cross-track differences are small. As a result, the updated NHC track is very similar to the previous advisory, and is close to a consensus of the ECMWF, GFS, UKMET, and HWRF, but is not as far south as the latest runs of the UKMET or ECMWF.

Irma is forecast to move over slightly warmer SSTs and into a moistening mid-level environment. These conditions, along with a favorable upper-level wind pattern, should allow for gradual strengthening during the next 2 to 3 days. However, eyewall replacement cycles could result in fluctuations in intensity during the next several days.

While Irma is currently a small hurricane, the guidance suggests it should grow in size during the next 72 h. This will affect how soon watches may be issued for portions of the Leeward and Virgin Islands, and interests on those islands should continue to monitor Irma’s progress.

KEY MESSAGES:
1. Irma is expected to be a major hurricane when it moves near or over the northeastern Leeward Islands by the middle of this week, and could cause dangerous wind, storm surge, and rainfall impacts, along with rough surf and rip currents on some islands. Hurricane and tropical storm watches will likely be issued for some of these islands later today or tonight. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

2. Direct impacts from Irma are also possible in the Virgin Islands and Puerto Rico later this week, and tropical storm or hurricane watches could be issued for these islands by tomorrow. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

3. The possibility of direct impacts from Irma in Hispaniola, the Turks and Caicos, and the Bahamas later this week is increasing. Residents in these areas should monitor the progress of Irma and listen to advice given by officials.

4. It is too early to determine what direct impacts Irma might have on the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 03/1500Z 17.7N 48.4W 115 MPH Category 3 Hurricane (E of Antigua and Barbuda)
12H 04/0000Z 17.1N 50.1W 120 MPH Category 3 Hurricane (E of Antigua and Barbuda)
24H 04/1200Z 16.6N 52.2W 125 MPH Category 3 Hurricane (E of Antigua and Barbuda)
36H 05/0000Z 16.4N 54.3W 130 MPH Category 4 Hurricane (E of Antigua and Barbuda)
48H 05/1200Z 16.7N 56.6W 140 MPH Category 4 Hurricane (E of Antigua and Barbuda)
72H 06/1200Z 18.2N 61.8W 140 MPH Category 4 Hurricane (E of Anguilla )
96H 07/1200Z 20.4N 67.1W 130 MPH Category 4 Hurricane (NW of San Juan, Puerto Rico)
120H 08/1200Z 22.5N 72.0W 130 MPH Category 4 Hurricane (N of Turks and Caicos)

Previous Warning  500 AM AST Sun Sep 03 2017

Irma’s convective pattern has improved slightly overnight. Very cold cloud tops completely encircle the eye, which has warmed and become a bit clearer in infrared satellite images. The initial intensity is raised to 100 kt based on a blend of the latest subjective and objective Dvorak estimates.

Irma has been losing latitude since yesterday due to strong high pressure to its north, and the initial motion is now west- southwestward, or 255/13 kt. The hurricane is likely to continue moving on this trajectory for the next 36 hours, after which time it should gradually turn toward the west and then west-northwest on days 3-5 when it reaches the western extent of the ridge. The new NHC track forecast is very similar to the previous one during the first 48 hours, showing Irma bottoming out around 16.5N.

However, the track guidance has shifted westward after 48 hours, delaying a turn toward the west-northwest, and this required a corresponding westward shift in the official forecast toward the multi-model consensus at the end of the forecast period. It should be noted that the official forecast still lies to the east of some of the better-performing models, such as the ECMWF, HWRF, and HCCA, so additional adjustment are possible in subsequent advisories.

The environment ahead of Irma appears conducive for gradual strengthening for at least the next 2 to 3 days, with increasing sea surface temperatures and a moistening in the mid-levels of the atmosphere. We may still observe fluctuations in intensity, but overall, the model guidance seems to suggest a general upward trend with a peak in intensity possibly occurring around day 3. This type of intensification would coincide with the timing of Irma’s west-southwest to westward motion, a pattern which we have observed in other west-southwestward-moving hurricanes in the past (i.e., Katrina, Joaquin, Fernanda, etc.). The NHC intensity forecast is bumped up slightly, showing a peak in intensity on day 3, and is largely a blend of the ICON intensity consensus and HCCA.

While Irma is currently a small hurricane, the size guidance suggests it should grow in size during the next 72 h. This will affect how soon watches may be issued for portions of the Leeward and Virgin Islands, and interests on those islands should continue to monitor Irma’s progress.

KEY MESSAGES:

1. Irma is expected to be a major hurricane when it moves closer to the Lesser Antilles over the next few days, producing rough surf and rip currents. Irma could also cause dangerous wind, storm surge, and rainfall impacts on some islands, although it is too soon to specify where and when those hazards could occur. Residents in the Lesser Antilles should monitor the progress of Irma through the weekend and listen to any advice given by local officials.

2. It is much too early to determine what direct impacts Irma will have on the Bahamas and the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their  hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 03/0900Z 18.0N 47.5W 115 MPH Category 3 Hurricane (NE of  of Antigua and Barbuda)
12H 03/1800Z 17.5N 49.1W 115 MPH Category 3 Hurricane (NE of  of Antigua and Barbuda)
24H 04/0600Z 16.8N 51.3W 120 MPH Category 3 Hurricane (NE of  of Antigua and Barbuda)
36H 04/1800Z 16.5N 53.4W 125 MPH Category 3 Hurricane (NE of  of Antigua and Barbuda)
48H 05/0600Z 16.5N 55.7W 130 MPH Category 4 Hurricane (NE of Antigua and Barbuda)
72H 06/0600Z 17.8N 60.6W 140 MPH Category 4 Hurricane (NE of Antigua and Barbuda)
96H 07/0600Z 20.0N 66.0W 130 MPH Category 4 Hurricane (NE of San Juan, Puerto Rico)
120H 08/0600Z 22.5N 71.5W 130 MPH Category 4 Hurricane (NE of Turks and Caicos)

Previous Warning  1100 PM AST Sat Sep 02 2017

The cloud pattern of Irma has not changed significantly in structure today. The eye continues to become apparent and then hide under the convective canopy, and this has been the observed pattern for the past 24 hours or so. Dvorak estimates go up and down with the presence of the eye, but an average of these numbers supports an initial intensity of 95 kt. A NOAA Hurricane Hunter plane will help with the intensity estimate on Sunday.

I hesitate to speculate too much about the environment that Irma is  embedded within. All of the standard ingredients necessary for strengthening are forecast to be at least marginally favorable, but none are expected to be hostile for intensification. The NHC forecast, which in fact is similar to the previous one, continues tobe a blend of the statistical models and the explosive strengthening shown by the regional hurricane and global models.

The subtropical ridge building to the north of Irma has been steering the hurricane toward the west or 260 degrees at 12 kt. The ridge is forecast to amplify even more, and this flow pattern will force the hurricane to dive west-southwestward for a couple of days. Irma should then begin to gain latitude once it reaches the southwestern edge of the ridge in about 3 days. The confidence in the track forecast is high for the next 72 hours sinceall of the reliable guidance is basically on top of each other. After 3 days, when the hurricane is forecast to be approaching the northern Leeward Islands, the guidance envelope spreads out and becomes bounded by the southernmost tracks of the HWRF, HCCA and the ECMWF models, and by the northernmost GFS and UK models. The confidence beyond 3 days is then much lower. Tonight’s NHC forecast was adjusted a just little to the south of the previous one due to another small shift of the guidance envelope. The forecast is basically on top of the multi-model consensus TVCX.

While Irma is currently a small hurricane, the size guidance suggests it should grow in size during the next 72 h. This will affect how soon watches may be issued for portions of the Leeward and Virgin Islands

KEY MESSAGES:

1. Irma is expected to be a major hurricane when it moves closer to the Lesser Antilles early next week, producing rough surf and rip currents. Irma could also cause dangerous wind, storm surge, and rainfall impacts on some islands, although it is too soon to specify where and when those hazards could occur. Residents in the Lesser Antilles should monitor the progress of Irma through the weekend and listen to any advice given by local officials.

2. It is much too early to determine what direct impacts Irma will have on the Bahamas and the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 03/0300Z 18.3N 46.2W 110 MPH Category 2 Hurricane (NE of Antigua and Barbuda)
12H 03/1200Z 17.8N 48.0W 110 MPH Category 2 Hurricane (NE of Antigua and Barbuda )
24H 04/0000Z 17.2N 50.1W 115 MPH Category 3 Hurricane (NE of Antigua and Barbuda )
36H 04/1200Z 16.7N 52.3W 120 MPH Category 3 Hurricane (NE of Antigua and Barbuda )
48H 05/0000Z 16.5N 54.5W 125 MPH Category 3 Hurricane (NE of Antigua and Barbuda )
72H 06/0000Z 17.7N 59.3W 125 MPH Category 3 Hurricane (NE of Antigua and Barbuda )
96H 07/0000Z 19.9N 64.5W 130 MPH Category 4 Hurricane (NE of British Virgin Islands)
120H 08/0000Z 22.5N 69.5W 130 MPH Category 4 Hurricane (NE of Turks and Caicos )

Previous Warning 500 PM AST Sat Sep 02 2017

Hurricane Irma continues to display an eye within a small central dense overcast, although the eye has been going through periods where it becomes less well defined. The satellite intensity estimates from TAFB and SAB remain 90 kt, while the latest CIMMS ADT and satellite consensus technique estimates ARE 95-105 KT. Since there has been little overall change in organization since the last advisory, the initial intensity remains 95 kt.

The environment in which Irma is embedded continues to show mixed signals during the forecast period, and the intensity guidance responds to this by ranging between little and slow intensification. The hurricane is currently suffering some impact of sea surface temperatures of about 27C and mid-level dry air entrainment. Later in the period, Irma should encounter warmer water and increasing moisture at a time when the vertical wind shear may be increasing. Given the uncertainty on when all of the ingredients may come together, the new intensity forecast is the same as the previous forecast and calls for gradual intensification through the next 5 days. An alternative forecast scenario is that Irma gets significantly stronger than forecast near the end of the forecast period if the shear is less than currently expected.

The initial motion remains 265/13. A large and building subtropical ridge should steer Irma generally west-southwestward during the next two days or so. Between 72-120 h, Irma should be rounding the southwestern periphery of the ridge and start turning back toward the west-northwest. While the track guidance remains in good agreement with this scenario, from 72-120 h there has been a westward shift of the guidance that results in the new forecast track coming 30-60 n mi closer to the Leeward and Virgin Islands than in the previous advisory. This latter portion of the track lies near the center of the guidance envelope, but with the ECMWF and corrected consensus models to the south and the GFS to the north.

While Irma is currently a small hurricane, the size guidance suggests it should grow in size during the next 72 h. This will affect how soon watches may be issued for portions of the Leeward and Virgin Islands.

KEY MESSAGES:

1. Irma is expected to be a major hurricane when it moves closer to the Lesser Antilles early next week, producing rough surf and rip currents. Irma could also cause dangerous wind, storm surge, and rainfall impacts on some islands, although it is too soon to specify where and when those hazards could occur. Residents in the Lesser Antilles should monitor the progress of Irma through the weekend and listen to any advice given by local officials.

2. It is much too early to determine what direct impacts Irma will have on the Bahamas and the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 02/2100Z 18.5N 44.6W 110 MPH Category 2 Hurricane (NE of  Antigua and Barbuda)
12H 03/0600Z 18.0N 46.5W 110 MPH  Category 2 Hurricane (NE of  Antigua and Barbuda)
24H 03/1800Z 17.4N 48.8W 115 MPH  Category 3 Hurricane (NE of  Antigua and Barbuda)
36H 04/0600Z 17.0N 50.9W 120 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
48H 04/1800Z 16.8N 53.0W 125 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
72H 05/1800Z 17.5N 57.5W 125 MPH  Category 3 Hurricane (NE of  Antigua and Barbuda)
96H 06/1800Z 19.5N 62.5W 130 MPH  Category 4 Hurricane (NE of Anguilla)
120H 07/1800Z 22.0N 68.0W 130 MPH  Category 4 Hurricane (E of Turks and Caicos )

Previous Warning  1100 AM AST Sat Sep 02 2017

Hurricane Irma continues to display an eye within a small central dense overcast in the visible and infrared imagery from the GOES and METEOSAT satellites. Dvorak current intensity numbers from TAFB, SAB, and the CIMSS ADT have not changed, so the intensity remains 95 kt.

The environment in which Irma is embedded shows mixed signals for the next few days. While the vertical shear remains low through Monday, the SSTs are lukewarm and mid-level humidities are dry. (Indeed an overnight SSMIS microwave pass showed a distinct finger of dry air wrapping around the south side of Irma not far from its inner core.) However, after the waters warm and the atmosphere moistens at days 3-5, the shear is forecast to go up. The guidance has substantial spread between Category 2 and 4 by the end of the forecast period. The official intensity forecast is based upon a blend of the LGEM/DSHP statistical techniques and the HWRF dynamical model and is unchanged from the previous advisory.

Irma is finally moving slightly south of due west at 13 kt. A large, building Azores-Bermuda high should turn Irma toward the west-southwest at a slower rate of speed during the next two days. By days 3 to 5, Irma should be rounding the southwestern periphery of the high and start turning back toward the west-northwest. The track guidance is in tight agreement with this scenario and the official forecast is a simply an update from the previous advisory.

Irma is a small hurricane, as observed by ship BATFR17 and the overnight ASCAT scatterometer pass with tropical-storm-force winds extending out at most about 60 nm. The official size forecast is based upon the RVCN multi-model consensus technique.

KEY MESSAGES:

1. Irma is expected to be a major hurricane when it moves closer to the Lesser Antilles early next week, producing rough surf and rip currents. Irma could also cause dangerous wind, storm surge, and rainfall impacts on some islands, although it is too soon to specify where and when those hazards could occur. Residents in the Lesser Antilles should monitor the progress of Irma through the weekend and
listen to any advice given by local officials.

2. It is much too early to determine what direct impacts Irma will have on the Bahamas and the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 02/1500Z 18.8N 43.3W 110 MPH  Category 2 Hurricane (NE of  Antigua and Barbuda)
12H 03/0000Z 18.5N 45.0W 110 MPH  Category 3 Hurricane (NE of  Antigua and Barbuda)
24H 03/1200Z 18.0N 47.4W 115 MPH  Category 3 Hurricane (NE of  Antigua and Barbuda)
36H 04/0000Z 17.4N 49.5W 120 MPH  Category 3 Hurricane (NE of  Antigua and Barbuda)
48H 04/1200Z 17.1N 51.6W 125 MPH  Category 3 Hurricane (NE of  Antigua and Barbuda)
72H 05/1200Z 17.4N 56.0W 125 MPH  Category 3 Hurricane (NE of  Antigua and Barbuda)
96H 06/1200Z 19.2N 60.6W 130 MPH  Category 4 Hurricane (NE of  Anguilla)
120H 07/1200Z 22.0N 66.0W 130 MPH  Category 4 Hurricane (N of San Juan, Puerto Rico)

Previous Warning 500 AM AST Sat Sep 02 2017

Irma appears to have weakened a little during the last several hours. The eye has become cloud filled once again, and the convective pattern is not as impressive as it was yesterday. A blend of the latest Dvorak classifications from TAFB/SAB and ADT values from CIMSS at the University of Wisconsin support lowering the initial wind speed a little to 95 kt. It is interesting to note that a ship (BATFR17) passed within 50 n mi to the west of the center of Irma and has only reported winds of about 40 kt, indicating that the core of Irma is compact.

The observed fluctuations in strength during the past day or so are likely to continue for about another day while Irma remains over marginally warm waters and in fairly close proximity to dry air. Eyewall replacement cycles, like the one observed yesterday, could occur, but forecasting the timing and duration of these are not possible. After 24 hours, Irma is expected to move over progressively warmer waters and into a more moist environment.
These more favorable conditions combined with low to moderate wind shear should allow the hurricane to strengthen. The NHC intensity forecast follows the consensus aids HCCA and IVCN, and it is fairly similar to the previous advisory.

Irma is now moving due west at 12 kt. A subtropical high pressure system to the north of the hurricane is expected to strengthen and build westward during the next couple of days. This pattern should cause Irma to move west-southwestward during that time. Thereafter, a turn back to the west and then west-northwest is predicted in the 3-5 day time period when Irma moves on the south and southwest sides of the high. Although the models agree on the overall scenario, there remains about 200 n mi north-south spread among the best-performing models on day 5. The NHC track forecast has been adjusted to the south at the longer-range points, and it is about halfway between the latest runs of the GFS and ECMWF models.

KEY MESSAGES:

1. Irma is expected to be a major hurricane when it moves closer to the Lesser Antilles early next week, producing rough surf and rip currents. Irma could also cause dangerous wind, storm surge, and rainfall impacts on some islands, although it is too soon to specify where and when those hazards could occur. Residents in the Lesser Antilles should monitor the progress of Irma through the weekend and listen to any advice given by local officials.

2. It is much too early to determine what direct impacts Irma will have on the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0900Z 19.0N 41.8W 110 MPH Category 2 Hurricane (NE of  Antigua and Barbuda)
12H 02/1800Z 18.8N 43.7W 115 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
24H 03/0600Z 18.3N 46.1W 115 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
36H 03/1800Z 17.7N 48.3W 120 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
48H 04/0600Z 17.1N 50.4W 125 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
72H 05/0600Z 17.0N 54.7W 125 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
96H 06/0600Z 18.4N 59.3W 130 MPH  Category 4 Hurricane (NE of  Antigua and Barbuda)
120H 07/0600Z 21.0N 64.5W 130 MPH Category 4 Hurricane (N of  British Virgin Islands)

Previous Warning 1100 PM AST Fri Sep 01 2017

After developing a nearly clear eye during the afternoon hours, Irma appears to have once again temporarily peaked. A WindSat pass around 2100 UTC hinted at the beginning of another eyewallreplacement cycle, which would be consistent with the observed cooling of the eye. However, the small size of the hurricane’s inner core relative to the resolution of the microwave instrument makes it impossible for me to say for sure. The initial intensity has been lowered slightly to 100 kt, but it should be stressed that this is probably just another fluctuation, in what will likely be a long string of small changes in intensity over the next several days. Since we do not have the ability to predict such changes, the NHC forecast shows very gradual intensification throughout the forecast period, given the warm SSTs and increasing moisture content along the forecast track. The NHC forecast is near the intensity consensus, but slightly favors the higher dynamical models.

The initial motion remains 275/12 kt. The hurricane has moved a little farther north than previously expected, and the track has been adjusted in that direction. Overall, the reasoning behind the track forecast has not changed, and Irma is still expected to turn west-southwestward on Saturday due to a building ridge over the central Atlantic. After about 72 h, there remains a large north-south spread in the guidance, with the GFS continuing to show
a weaker ridge (and a northern track), while the ECMWF shows a stronger ridge/southern track. The ECMWF has performed better for Irma thus far, so my forecast continues to favor that solution.

KEY MESSAGES:

1. Irma is expected to be a major hurricane when it approaches the Lesser Antilles early next week, producing rough surf and rip currents. Irma could also cause dangerous wind, storm surge, and rainfall impacts on some islands, although it is too soon to specify where and when those hazards could occur. Residents in the Lesser\ Antilles should monitor the progress of Irma through the weekend and listen to any advice given by local officials.

2. It is much too early to determine what direct impacts Irma will have on the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 19.1N 40.5W 115 MPH  Category 3 Hurricane (NE of Antigua and Barbuda)
12H 02/1200Z 19.0N 42.3W 115 MPH  Category 3 Hurricane (NE of Antigua and Barbuda)
24H 03/0000Z 18.5N 44.6W 120 MPH  Category 3 Hurricane (NE of Antigua and Barbuda)
36H 03/1200Z 17.9N 46.9W 125 MPH  Category 3 Hurricane (NE of Antigua and Barbuda)
48H 04/0000Z 17.3N 49.0W 125 MPH  Category 3 Hurricane (E of Antigua and Barbuda)
72H 05/0000Z 16.8N 53.3W 125 MPH  Category 3 Hurricane (SE of Antigua and Barbuda)
96H 06/0000Z 18.0N 57.5W 130 MPH Category 4 Hurricane (SE of  Anguilla)
120H 07/0000Z 20.5N 62.5W 130 MPH Category 4 Hurricane (NE of  Anguilla)

Previous Warning 500 PM AST Fri Sep 01 2017

Well, that eyewall replacement cycle didn’t last long. Satellite images indicate that the cycle is now complete, with Irma displaying a larger warm eye. The initial wind speed has been set to 105 kt, in agreement with the CIMSS ADT. Since the eyewall cycle is finished, some strengthening is possible, although SSTs are currently pretty marginal. Although no increase in winds is shown in the short term, this could be conservative. During the next few days, water temperatures along the track will warm significantly, but there could be some higher shear, and of course more eyewall replacements. The forecast is a compromise between the statistical/dynamical models, which bring the intensity down then upagain, versus the global models and hurricane models, which show a rather strong cyclone.

The westward turn of Irma has begun, and the current motion is 275/12. A building mid-level high should cause the hurricane to turn west southwestward tomorrow and continue through early next week. Later on, Irma should reach the southern periphery of the ridge, and begin to move west-northwestward. The biggest change since the last forecast is that the GFS and its ensemble has trended southwestward, toward the unwavering ECMWF model on the track forecast. Given the trend in guidance, little change is made to the official track prediction, although the corrected consensus models and the HWRF are now southwest of the latest forecast.

KEY MESSAGES:

1. Irma is expected to be a major hurricane when it approaches the Lesser Antilles early next week, producing rough surf and rip currents. Irma could also cause dangerous wind, storm surge, and rainfall impacts on some islands, although it is too soon to specify where and when those hazards could occur. Residents in the Lesser Antilles should monitor the progress of Irma through the weekend and listen to any advice given by local officials.

2. It is much too early to determine what direct impacts Irma will have on the continental United States. Regardless, everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season.

FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 18.8N 39.1W 120 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
12H 02/0600Z 18.9N 40.9W 120 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
24H 02/1800Z 18.5N 43.4W 120 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
36H 03/0600Z 17.9N 45.7W 120 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
48H 03/1800Z 17.2N 47.9W 120 MPH Category 3 Hurricane (E of Antigua and Barbuda)
72H 04/1800Z 16.4N 52.2W 125 MPH Category 3 Hurricane (SE of Antigua and Barbuda)
96H 05/1800Z 17.0N 56.5W 125 MPH Category 3 Hurricane (SE of Antigua and Barbuda)
120H 06/1800Z 19.0N 61.0W 130 MPH Category 4 Hurricane (NE of  Anguilla)

Previous Warning 1100 AM AST Fri Sep 01 2017

LOCATION…18.5N 37.8W
ABOUT 1580 MI…2540 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS…110 MPH…175 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 13 MPH…20 KM/H
MINIMUM CENTRAL PRESSURE…972 MB…28.71 INCHES

At 1100 AM AST (1500 UTC), the center of Hurricane Irma was located near latitude 18.5 North, longitude 37.8 West. Irma is moving toward the west-northwest near 13 mph (20 km/h). A turn toward the west is expected by tonight, followed by a turn toward the west-southwest on Saturday.

Maximum sustained winds are near 110 mph (175 km/h) with higher gusts. Fluctuations in strength, up or down, are possible during the next few days, but Irma is expected to remain a powerful hurricane through the weekend.

Hurricane-force winds extend outward up to 15 miles (30 km) from the center and tropical-storm-force winds extend outward up to 90 miles (150 km). The estimated minimum central pressure is 972 mb (28.71 inches).

Irma is undergoing an eyewall replacement cycle. The small eye is becoming less distinct, with both microwave and visible imagery indicating the presence of a forming outer eyewall. Satellite intensity estimates are lower, so the initial wind speed is reduced to 95 kt. Some further weakening is possible over the next day or so while Irma moves over marginally warm SSTs and continues the eyewall replacement. After that time, the environment should be generally conducive for some restrengthening, although forecasting the timing of eyewall replacement cycles is next to impossible. The biggest change from yesterday are the long-term wind shear predictions from the global models, which shows a little more shear. Still, the shear is not that strong, and the hurricane will be moving over 29C SSTs. Thus, the NHC intensity forecast is reduced somewhat from the previous one, but remains near or slightly abovethe model consensus.

Irma has turned a little bit to the left, now estimated to be moving 285/11. The general synoptic situation remains well established due to a building mid-level high, which should cause the hurricane to turn westward later today and then move west-southwestward through the weekend. An upper-level low will be dropping southward on the east side of that high, and should be a key feature to how far south Irma goes before eventually turning westward and west-northwestward early next week. There is a noticeable clustering of guidance by day 5, with the ECMWF, HWRF and corrected-consensus models to the south, and the UKMET, GFS, CTC and HMON to the north. Since Irma is forecast to be a vertically deep cyclone, it seems more likely to respond to the northerly flow from the upper-level low, which leads me to believe the track will be on the southern side of the guidance. Thus, the forecast will stay similar to the previous one, very close to the southern cluster mentioned above.

FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 18.5N 37.8W 110 MPH   Category 2 Hurricane (NE of Antigua and Barbuda)
12H 02/0000Z 18.7N 39.5W 105 MPH Category 2 Hurricane (NE of Antigua and Barbuda)
24H 02/1200Z 18.5N 41.8W 105 MPH Category 2 Hurricane (NE of Antigua and Barbuda)
36H 03/0000Z 18.0N 44.2W 110 MPH  Category 2 Hurricane (NE of Antigua and Barbuda)
48H 03/1200Z 17.3N 46.6W 115 MPH  Category 3 Hurricane (NE of Antigua and Barbuda)
72H 04/1200Z 16.2N 51.0W 120 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
96H 05/1200Z 16.7N 55.2W 125 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
120H 06/1200Z 18.0N 59.5W 125 MPH Category 3 Hurricane (NE of Antigua and Barbuda)

Previous Warning 500 AM AST Fri Sep 01 2017

At 500 AM AST (0900 UTC), the center of Hurricane Irma was located near latitude 18.2 North, longitude 36.5 West. Irma is moving toward the west-northwest near 12 mph (19 km/h). A turn toward the west is expected by tonight, followed by a turn toward the west-southwest on Saturday.

Maximum sustained winds remain near 115 mph (185 km/h) with higher gusts. Irma is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Fluctuations in strength, up or down, are possible during the next few days, but Irma is expected to remain a powerful hurricane through the weekend.

Hurricane-force winds extend outward up to 15 miles (30 km) from the center, and tropical-storm-force winds extend outward up to 90 miles
(150 km). The estimated minimum central pressure is 967 mb (28.56 inches).

12H 01/1800Z 18.5N 38.2W 115 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
24H 02/0600Z 18.4N 40.5W 115 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
36H 02/1800Z 18.2N 42.9W 115 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
48H 03/0600Z 17.6N 45.2W 120 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
72H 04/0600Z 16.5N 49.3W 125 MPH Category 3 Hurricane (NE of Antigua and Barbuda)
96H 05/0600Z 16.5N 53.5W 130 MPH Category 4 Hurricane (NE  of Antigua and Barbuda)
120H 06/0600Z 17.5N 58.0W 140 MPH  Category 4 Hurricane (NE of Antigua and Barbuda)

Previous Warning 1100 PM AST Thu Aug 31 2017

The period of rapid intensification that began in earnest about 24 hours ago appears to have ended, at least for now. Although a ring of very cold cloud tops continues to surround a small eye, the eye appears to have filled somewhat during the evening hours. This may be due to an eyewall replacement cycle that was noted to have begun earlier today. A lack of recent microwave imagery makes it difficult to confirm that, however. The initial intensity remains 100 kt based on a blend of subjective and objective Dvorak current intensity estimates.

Even though the intensification of Irma seems to have stopped for now, the hurricane is still embedded within a favorable environment. For the next couple days, internal convective variability, especially eyewall replacement cycles, may cause the intensity to fluctuate up or down. Most of the guidance through this period shows very little change in strength. Beyond 48 hours, Irma will move over much warmer SSTs, and all of the hurricane models forecast some strengthening. The NHC forecast remains a little above the intensity consensus, and is close to the HWRF and HMON models.

The initial motion estimate is 295/10 kt. No significant changes have been made to the track forecast. While there remains good agreement among the dynamical models that a ridge building over the central Atlantic will steer Irma toward the west on Friday, and the west-southwest through the weekend, there is large spread beyond 72 h. For example, the GFS shows a somewhat weaker Irma and a weaker ridge, forcing the hurricane to move slower and make a sharper turn back toward the west-northwest. On the other hand, the ECMWF and HWRF depict a stronger ridge and a stronger hurricane on a more southern track. Since my forecast calls for strengthening, the NHC forecast remains south of the multi-model consensus, but is a little north of the corrected consensus, HCCA.

FORECAST POSITIONS AND MAX WINDS

INIT 01/0300Z 17.8N 35.6W – 115 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
12H 01/1200Z 18.1N 37.0W – 115 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
24H 02/0000Z 18.3N 39.2W – 115 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
36H 02/1200Z 18.2N 41.5W – 115 MPH Category 3 Hurricane (NE of  Antigua and Barbuda)
48H 03/0000Z 17.7N 43.8W – 120 MPH Category 3 Hurricane (E of  Antigua and Barbuda)
72H 04/0000Z 16.7N 48.2W – 125 MPH Category 3 Hurricane (SE of  Antigua and Barbuda)
96H 05/0000Z 16.3N 52.4W – 130 MPH Category 4 Hurricane   (SE of  Antigua and Barbuda)
120H 06/0000Z 17.0N 57.0W – 140 MPH Category 4 Hurricane (SE of  Antigua and Barbuda)

Previous Warning 500 PM AST Thu Aug 31 2017

Irma has become an impressive hurricane with intense eyewall convection surrounding a small eye. Satellite estimates continue to rapidly rise, and the Dvorak classifications from both TAFB & SAB
support an initial wind speed of 100 kt. This is a remarkable 50-kt increase from yesterday at this time.

Microwave and satellite data suggest that an eyewall replacement cycle could be starting. This isn’t surprising given how small the eye is, and will probably be the first of many eyewall cycles for this hurricane. Overall, Irma should be in a low-shear environment for several days, with the intensity controlled by eyewall cycles and the moderately warm SSTs along the path. Thus the forecast intensity is leveled off for the next 2 days. After the weekend, Irma should be moving over much warmer water, with SSTs forecast to be 29C at the end of the period. All indications are for Irma to be strengthening by the end of the forecast period, with the NHC prediction adjusted slightly upward from the previous one, in line with the extremely low pressures forecast by the global and regional hurricane models at that time.

Irma continues moving west-northwestward, now at about 10 kt. There has been no change to the forecast philosophy, with the hurricane likely to turn westward and west-southwestward over the next few days due to a building ridge over the central Atlantic. At long range, however, model guidance is not in good agreement on the strength of the ridge, resulting in some significant north-south differences in the global models. I am inclined to stay on the southwestern side of the model guidance, given the rather consistent forecasts of the ECMWF and its ensemble. In addition, the strongest members of the recent ensembles are on the southern side on the consensus, giving some confidence in that approach.

FORECAST POSITIONS AND MAX WINDS

INIT 31/2100Z 17.3N 34.8W 115 MPH Category 3 Hurricane (NW of Cape Verde Islands)
12H 01/0600Z 17.8N 36.2W 120 MPH Category 3 Hurricane (NW of Cape Verde Islands)
24H 01/1800Z 18.2N 38.3W 120 MPH  Category 3 Hurricane (NW of Cape Verde Islands)
36H 02/0600Z 18.3N 40.7W 120 MPH  Category 3 Hurricane (NW of Cape Verde Islands)
48H 02/1800Z 17.9N 42.9W 120 MPH  Category 3 Hurricane (SE of  Antigua and Barbuda)
72H 03/1800Z 16.8N 47.5W 125 MPH  Category 3 Hurricane  (SE of  Antigua and Barbuda)
96H 04/1800Z 16.0N 52.0W 130 MPH  Category 4 Hurricane (E of Guadeloupe)
120H 05/1800Z 16.5N 56.5W 140 MPH  Category 4 Hurricane (SE of  Antigua and Barbuda)

Previous Warning 1100 AM AST Thu Aug 31 2017

Satellite images indicate that Irma is rapidly intensifying. Very deep convection has formed in the central dense overcast, which is now displaying a small and clearing eye. Dvorak estimates were up to 77 kt at 1200 UTC, and since the cloud pattern continues to quickly become more organized, the initial wind speed is set to 85 kt.

Irma has moved somewhat south of and slower than all of the model guidance since yesterday. Consequently, it stayed longer over the warmer ocean temperatures away from the drier air to the north,
possibly allowing the rapid strengthening. Irma should move over cooler waters tomorrow with some increase in mid-level dry air, so hopefully the hurricane’s intensity will level off by then. In a few days, the hurricane will be moving over warmer waters with light shear shown by all of the model guidance. This should promote further strengthening of Irma, and the NHC forecast shows an
extremely dangerous category 4 hurricane next week, similar to the solutions provided by the HWRF and the ECMWF models. The intensity forecast is raised considerably from the previous one due to initial trends, and is on the high end of the guidance at long range.

The hurricane has turned west-northwestward at about 9 kt. This motion should continue for the next day or so before a ridge builds over the central Atlantic Ocean. This ridge should force Irma to turn westward by the weekend, and west-southwestward early next week. Guidance continues to trend southward, following the trend of the ECMWF model starting yesterday. Given the strength of the ridge and depth of the tropical cyclone, there are no obvious reasons to discount the anomalous west-southwestward motion seen in most of the guidance. Little change is made to the track forecast in short range, but the track is shifted southward and westward at long range, though not as far southwest as the overnight ECMWF and ECMWF
ensemble models.

FORECAST POSITIONS AND MAX WINDS

INIT 31/1500Z 16.9N 33.8W – 100 MPH Category 2 Hurricane (SE of Puerto Rico)
12H 01/0000Z 17.5N 35.2W – 115 MPH Category 3 Hurricane (SE of Puerto Rico)
24H 01/1200Z 18.0N 37.1W – 120 MPH Category 3 Hurricane (SE of Puerto Rico)
36H 02/0000Z 18.2N 39.2W – 120 MPH Category 3 Hurricane  (SE of Puerto Rico)
48H 02/1200Z 18.1N 41.6W –  120 MPH Category 3 Hurricane  (E of Puerto Rico)
72H 03/1200Z 17.0N 46.5W – 125 MPH Category 3 Hurricane (SE of Antigua and Barbuda)
96H 04/1200Z 16.0N 51.0W – 125 MPH Category 3 Hurricane (NE of Dominica)
120H 05/1200Z 16.0N 55.5W – 130 MPH  Category 4 Hurricane (SE of Guadeloupe)

Previous Warning  500 AM AST Thu Aug 31 2017

At 500 AM AST (0900 UTC), the center of Tropical Storm Irma was located near latitude 16.5 North, longitude 32.9 West. Irma is moving toward the west near 12 mph (19 km/h). A west-northwestward motion is expected today and tonight, followed by a generally westward motion on Friday Maximum sustained winds have increased to near 70 mph (110 km/h) with higher gusts. Additional strengthening is forecast, and Irma is likely to become a hurricane later today. Tropical-storm-force winds extend outward up to 60 miles (95 km) from the center. The estimated minimum central pressure is 997 mb (29.44 inches).

Irma continues to become better organized with a developing CDO and a few banding features. The overall cloud pattern is fairly symmetric, with fair upper-level outflow over all but the southeastern portion of the circulation.  The environment ahead of Irma appears to be mostly conducive for intensification, with increasingly warm SSTs. Vertical shear is expected to remain low as an upper-level trough to the west-northwest of the tropical cyclone lifts out to the north and west. The only noticeable inhibiting factor is slightly drier mid-level air in 2-5 days, but this will probably not be much of a deterrent for strengthening. The official intensity forecast follows the latest consensus of the models, and is similar to the previous NHC prediction.

Based on geostationary satellite fixes, the initial motion is just slightly north of west or 280/10 kt. Most of the track guidance shows a west northwestward motion for the next day or so. Irma will remain situated to the south of a well-defined mid-tropospheric ridge through the forecast period. Much of the guidance indicates that Irma will turn toward a slightly south of westward heading in a couple of days, presumably in response to some building of high pressure to the north and northwest. The official track forecast also shows this, and remains on the southern side of the guidance suite. This is mainly a blend of the GFS and ECMWF solutions.

FORECAST POSITIONS AND MAX WINDS
12H 31/1800Z 17.0N 34.2W – 80 MPH Category 1 Hurricane  (E of Antigua and Barbuda)
24H 01/0600Z 17.6N 36.0W – 90 MPH Category 1 Hurricane  (E of Anguilla)
36H 01/1800Z 18.0N 37.9W – 100 MPH Category 2 Hurricane (E of Anguilla)
48H 02/0600Z 18.2N 40.1W – 105 MPH Category 2 Hurricane (E of Puerto Rico)
72H 03/0600Z 17.5N 45.0W – 115 MPH Category 3 Hurricane  (NE of Montserrat)
96H 04/0600Z 16.7N 49.5W – 120 MPH Category 3 Hurrican(SE of Antigua and Barbuda)
120H 05/0600Z 16.0N 53.5W – 120 MPH Category 3 Hurrican(SE of Guadeloupe

Previous Warning  1100 PM AST Thu Aug 30 2017

Irma continues to become better organized, with the development of a small CDO feature and increased banding near the center. An earlier high-resolution Windsat microwave overpass showed that Irma has a tight inner core and a low-level eye-like feature was present. A Dvorak classification of T3.5 from TAFB is the basis for the initial intensity of 55 kt. Irma is expected to steadily strengthen during the next couple of days while it moves through a low-shear and moist environment, and remains over warm sea surface temperatures. After that time, slightly cooler SSTs and lower mid-level moisture may temper the intensification process. However, the statistical aids, HWRF, and most of the consensus models make Irma a major hurricane by the end of the forecast period. The NHC forecast is fairly similar to the previous advisory through 48 hours, but is above the earlier forecast thereafter. The new official intensity forecast could still be a little conservative as it remains a little below the SHIPS/LGEM guidance and the ICON consensus at days 4 and 5.

Irma is moving westward at about 10 kt to the south of deep-layer ridge over the eastern Atlantic. The track forecast reasoning is about the same as the previous advisory, with Irma expected to turn west-northwestward on Thursday, then continue on that heading for a couple of days. The high pressure ridge over the central Atlantic is forecast to strengthen later this week, which is expected to result in Irma turning west-southwestward by the
weekend. There is still some spread among the track models, so the NHC forecast lies near a blend of the typically reliable GFS and ECMWF, and the HFIP corrected consensus. Hurricane Irma is currently project to be a major hurricane in the Caribbean.

FORECAST POSITIONS AND MAX WINDS

INIT 31/0300Z 16.4N 32.2W – 65 MPH (NW of Cape Verde Islands)
12H 31/1200Z 16.8N 33.6W – 75 MPH Category 1 Hurricane  (W of Cape Verde Islands)
24H 01/0000Z 17.3N 35.5W – 85 MPH Category 1 Hurricane  (E of Antigua and Barbuda)
36H 01/1200Z 17.7N 37.3W  – 100 MPH Category 2 Hurricane  (E of Puerto Rico
48H 02/0000Z 18.0N 39.5W – 105 MPH Category 2 Hurricane  (E of Puerto Rico)
72H 03/0000Z 17.6N 44.3W – 110 MPH Category 3 Hurricane  (E of Puerto Rico)
96H 04/0000Z 16.8N 49.0W – 115 MPH Category 3 Hurricane  (SE of Antigua and Barbuda)
120H 05/0000Z 16.2N 53.5W  – 120 MPH Category 3 Hurricane  (E of Montserrat)

Previous Warning 500 PM AST Wed Aug 30 2017

Irma is displaying increasingly organized symmetric and interlocking rain bands with a well-defined outflow as seen in the visible and infrared satellite imagery this afternoon.

Irma is embedded within very low tropospheric vertical shear currently and for the foreseeable future, as the tropical storm lies underneath the upper-level anticyclone. However, in about three days the SSTs and the mid-level humidities that Irma should start to encounter will become cooler and drier. The intensity guidance shows steady intensification for the next two to three days, then diverges in response to the low shear/not-as-favorable thermodynamical environment. The official intensity forecast is closest to the ICON consensus technique through three days, then shows no change to day five. This new forecast is higher than the previous advisory, but lower than ICON at day 4 and 5 (and thus may be conservative).

Irma is moving toward the west at about 13 kt along the south side of the deep-layer Azores high. A slight turn toward the west- northwest at a slower rate of forward speed is expected during the next three days. As the high strengthens, Irma is expected to turn toward the west-southwest around day 4. There is a moderate amount of spread among the normally reliable global and mesoscale models in this scenario. The official track forecast is based upon the HFIP Corrected Consensus Approach and is nearly the same as that from the previous advisory.

Despite the large overall envelope of the Irma’s circulation, the earlier ASCAT passes showed a very small area of tropical-storm- force winds – only 30 nm radius. The official size forecast is based upon the RVCN – variable consensus technique.

FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 16.4N 31.2W – 60 MPH (NE of Brazil)
12H 31/0600Z 16.8N 32.7W  – 70 MPH (NE of Brazil)
24H 31/1800Z 17.3N 34.5W – 80 MPH Category 1 Hurricane (NE of Brazil)
36H 01/0600Z 17.8N 36.2W – 90 MPH Category 1 Hurricane (N of Brazil)
48H 01/1800Z 18.2N 38.2W – 100 MPH Category 2 Hurricane (E of Puerto Rico)
72H 02/1800Z 18.2N 43.0W – 105 MPH Category 2 Hurricane (SE of Anguilla)
96H 03/1800Z 17.3N 47.8W – 105 MPH Category 2 Hurricane (E of Antigua and Barbuda)
120H 04/1800Z 16.5N 52.5W – 105 MPH Category 2 Hurricane (E of Guadeloupe)

Previous Warning 1100 AM EDT Wed Aug 30 2017

 

“At 1100 AM AST (1500 UTC), the center of Tropical Storm Irma was located near latitude 16.4 North, longitude 30.3 West. Irma is moving toward the west near 13 mph (20 km/h) and this general motion
is expected to continue for the next couple of days.

Satellite wind data indicate that the maximum sustained winds are near 50 mph (85 km/h) with higher gusts. Some strengthening is forecast during the next 48 hours and Irma could become a hurricane
on Friday. Tropical-storm-force winds extend outward up to 35 miles (55 km) from the center.

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

Satellite images indicate that the low pressure area in the far eastern Atlantic has become much better organized since yesterday, with many curved bands around the center. ASCAT data showed peak winds of about 42 kt, and after considering the small size of the circulation and some undersampling due to the resolution of the instrument, the initial wind speed is set to 45 kt. Global models indicate that the upper-level winds are likely to be favorable for strengthening of Irma during the next several days. However, Irma will be moving over more marginal water temperatures and into drier mid-level conditions, which should temper the intensification rate. The NHC solution is a blend of the intensity consensus and the statistical-dynamical hurricane models SHIPS and LGEM. At the end of the period, the forecast could turn out to be conservative if the very conducive environment shown in most of the global models emerges.

The initial motion estimate is 280/11. A ridge over the eastern Atlantic is forecast to steer Irma westward over the next few days. Thereafter, the ridge builds southwestward, which will likely cause the storm to move, somewhat unusually, toward the west-southwest. The official forecast puts more weight on the global models than the regional hurricane models, which appear to have a northward bias on this cycle. Thus, the NHC track prediction is on the southwestern side of the guidance envelope, although not as far in that direction as the ECMWF or its ensemble mean.”

FORECAST POSITIONS AND MAX WINDS

INIT 30/1500Z 16.4N 30.3W – 50 MPH (W of Cape Verde)
12H 31/0000Z 16.7N 31.9W – 60 MPH (NE of Brazil)
24H 31/1200Z 17.3N 33.8W – 65 MPH (NE of Brazil)
36H 01/0000Z 17.9N 35.7W  – 70 MPH (NE of Brazil)
48H 01/1200Z 18.2N 37.6W – 75 MPH (NE of Brazil)
72H 02/1200Z 18.7N 41.9W – 80 MPH (E of British Virgin Islands)
96H 03/1200Z 17.7N 46.5W – 85 MPH (NE of Antigua and Barbuda)
120H 04/1200Z 17.0N 51.0W – 90 MPH (E of Antigua and Barbuda)

Previous Warning 200 AM EDT Wed Aug 30 2017

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

A low pressure area is located just west of the Cabo Verde Islands. This system has changed little in organization over the past several hours, but any significant increase in the associated thunderstorm activity would result in the formation of a tropical depression within the next day or two. The system is forecast to move west-northwestward to westward at 15 to 20 mph over the tropical Atlantic during the next several days. Formation chance through 48 hours, high, 90 percent. Formation chance through 5 days, high, 90 percent.

Previous Warning 800 PM EDT Tue Aug 29 2017

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

The National Hurricane Center is issuing advisories on Tropical Storm Harvey, located just offshore of the upper Texas coast. The National Hurricane Center has issued the last advisory on Potential Tropical Cyclone Ten, located just east of the Outer Banks of North Carolina.

A low pressure area is located just west of the Cabo Verde Islands. This system continues to become better organized, and any significant increase in the associated thunderstorm activity would result in the formation of a tropical depression within the next day or two. The low is forecast to move generally west-northwestward at 15 to 20 mph over the tropical Atlantic during the next several days. Heavy rain is possible over portions of the northwestern Cabo Verde Islands for a few more hours. Formation chance through 48 hours, high, 90 percent. Formation chance through 5 days, high, 90 percent.

Previous Warning 200 PM EDT Tue Aug 29 2017

A low pressure area located just west of the Cabo Verde Islands has become better defined since yesterday. Any significant increase in the associated thunderstorm activity would result in the formation of a tropical depression within the next day or two.

The low is forecast to move generally west-northwestward at 15 to 20 mph over the tropical Atlantic during the next several days. Heavy rain is possible over portions of the northwestern Cabo Verde Islands through tonight.

Formation chance through 48 hours, high…80 percent. Formation chance through 5 days, high, 90 percent.

Previous Warning 800 AM EDT Tue Aug 29 2017

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

Showers and thunderstorms associated with a low pressure area near the Cabo Verde Islands have become better organized since yesterday. Environmental conditions are conducive for development, and a tropical depression is expected to form in 2 or 3 days over the eastern Atlantic.

The low is forecast to move generally west-northwest at 15 to 20 mph over the tropical Atlantic during the next several days. Heavy rain is possible over portions of the Cabo Verde Islands through Wednesday. Formation chance through 48 hours, high, 70 percent. Formation chance through 5 days, high, 90 percent.

Previous Warning 200 AM EDT Tue Aug 29 2017

1. A tropical wave and associated low pressure area located a couple of hundred miles southeast of the Cabo Verde Islands is producing disorganized showers and thunderstorms. Environmental conditions
are conducive for development, and a tropical depression could form within the next few days over the eastern Atlantic. The low is forecast to move generally westward at 15 to 20 mph over the tropical Atlantic during the next several days. Regardless of development, heavy rain is possible over portions of the Cabo Verde Islands through Wednesday. Formation chance through 48 hours, medium, 50 percent. Formation chance through 5 day, high, 80 percent.

Previous Warning 800 PM EDT Mon Aug 28 2017

1. A tropical wave and associated low pressure area located a few hundred miles southeast of the Cabo Verde Islands is producing disorganized showers and thunderstorms. Environmental conditions are conducive for development, and a tropical depression could form within the next few days over the eastern Atlantic. The low is forecast to move westward at 15 to 20 mph over the tropical Atlantic during the next several days. Regardless of development, heavy rain is possible over portions of the Cabo Verde Islands through Wednesday. Formation chance through 48 hours, medium, 50 percent. Formation chance through 5 days, high, 80 percent.

Previous Warning 800 AM EDT Mon Aug 28 2017

1. A tropical wave and associated low pressure area located just offshore of the coast of western Africa is producing a large area of showers and thunderstorms. This system has become better organized since yesterday, and a tropical depression could form in a few days over the eastern Atlantic.

The low is forecast to move westward at 15 to 20 mph over the tropical Atlantic during the next several days. Regardless of development, heavy rain is possible in portions of the Cabo Verde Islands through Wednesday.  Formation chance through 48 hours, low, 30 percent. Formation chance through 5 days, high, 70 percent.

Video:  LIVE: HURRICANE IRMA THREATENS FLORIDA