Tropical Storm Henri

Tropical Depression Henri Track 2300 Hours August 22 2021
Tropical Depression Henri Track 2300 Hours August 22 2021

Tropical Storm Henri Flash Flood RiskTropical Storm HenriNWS National Hurricane Center Miami FL 1100 PM EDT Sun Aug 22, 2021 (see 11:00 pm video below)

Henri has continued to weaken over land and synoptic surface observations indicate that its maximum winds have decreased to near 25 kt. A little more weakening is likely during the next 48 hours, and simulated satellite imagery from the global models indicate that the system will be post-tropical after its expected re-emergence into the Atlantic in 36 hours or so. Beyond 48 hours the dynamical guidance suggests that the system will lose its identity.

Satellite imagery and surface data indicate that the center is moving slowly west-northwestward, or 290/7 kt. Henri is interacting with another cyclonic circulation over the northeastern United States. As a result of this interaction, the tropical cyclone is expected to briefly come to a halt overnight, turn toward the east-northeast on Monday, and continue an east-northeastward motion into Tuesday. The official forecast track is similar to the dynamical model consensus, TVCN.

Although Henri’s winds are weakening, the cyclone will still continue to be a prolific rain producer, resulting in significant flooding across southern New England and portions of the northern mid-Atlantic states for the next day or two.

This is the last advisory by the National Hurricane Center on Henri. 

Key Messages:

  • 1. Heavy rainfall will continue to lead to considerable flash, urban, and small stream flooding, along with the potential for additional minor to isolated moderate river flooding over portions of Long Island, New England, eastern New York, New Jersey and northeast Pennsylvania.
FORECAST POSITIONS AND MAX WINDS

INIT  23/0300Z 41.9N  73.2W   25 KT  30 MPH - Depression (ENE Goshen,CT)
 12H  23/1200Z 42.1N  73.6W   25 KT  30 MPH - Depression (WNW West Copake,NY)
 24H  24/0000Z 42.4N  72.5W   25 KT  30 MPH - Depression (ENE Amherst,MA)
 36H  24/1200Z 42.8N  69.5W   25 KT  30 MPH - Post Tropical (ESE Seabrook,NH)
 48H  25/0000Z 43.4N  65.5W   20 KT  25 MPH - Post Tropical (WSW Baccaro,NS Canada)
 60H  25/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM EDT Sun Aug 22, 2021

Henri’s presentation in both satellite and radar imagery has degraded significantly since the previous advisory due to the cyclone having moved over much cooler water. An eyewall feature is no longer evident and clouds tops have warmed markedly in the inner-core region around the center. Data from an Air Force Reserve reconnaissance aircraft, NOAA Doppler weather radars, and surface observations indicate that Henri’s peak winds have decreased to 50 kt despite the central pressure remaining constant at about 987 mb.

Henri is moving north-northwestward or 335/10 kt. The cyclone is forecast to gradually turn northwestward later this afternoon and possibly even move westward before stalling near the New York-Connecticut border later tonight owing to interaction with a mid- to upper-level low located over he DelMarVa region. The latter system is expected to be absorbed by Henri by early Monday morning before ejecting out slowly eastward to east-northeastward across southern New England by Monday afternoon and evening. Henri is then forecast to cross the southern Gulf of Maine and Nova Scotia as a remnant low on Tuesday. The new NHC track forecast is a little to the west and south of the previous advisory track, and lies close to the tightly packed simple- and corrected-consensus track models.

Little change in strength is expected until Henri makes landfall in the Rhode Island-eastern Connecticut area this afternoon. After landfall, rapid weakening is forecast due to land interaction and entrainment of cooler air coming in off of the Atlantic Ocean. Henri should weaken to a tropical depression by early Monday, and become post-tropical by Monday afternoon or evening.

Due to the degraded radar presentation of Henri, hourly Tropical Cyclone Updates (TCU) will be discontinued after the 1100 AM EDT advisory.

Key Messages:

  • 1. Dangerous storm surge inundation is expected to continue today in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Residents in these areas should follow any advice given by local officials.
  • 2. Tropical storm conditions will continue in portions of the tropical storm warning area into tonight.
  • 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor to isolated moderate river flooding over portions of Long Island, New England, eastern New York, New Jersey and northeast Pennsylvania.
  • 4. Swells from Henri will continue to affect much of the east coast of the U.S. during the next day or so. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z 41.1N  71.6W   50 KT  60 MPH - Tropical Storm (WSW New Shoreham,RI)
 12H  23/0000Z 42.4N  73.2W   35 KT  40 MPH - Tropical Storm (WNW Washington, MA)
 24H  23/1200Z 43.0N  72.7W   30 KT  35 MPH - Tropical Storm (WNW Newfane,VT)
 36H  24/0000Z 43.3N  71.3W   25 KT  30 MPH - Post Tropical (ESE Pittsfield,NH)
 48H  24/1200Z 43.7N  68.7W   25 KT  30 MPH - Post Tropical (ESE Matinicus,ME)
 60H  25/0000Z 44.3N  64.5W   25 KT  30 MPH - Post Tropical (ESE Conquerall Mills,NS Canada)
 72H  25/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM EDT Sat Aug 21, 2021 

The convective pattern associated with Henri is less ragged than it was 6 h ago, as the convection has increased near the center and a NOAA Hurricane Hunter aircraft reported a 25 n mi wide eye has formed However, the hurricane has not yet strengthened significantly, as the maximum winds remain about 65 kt in the southeastern eyewall and the central pressure is near 987 mb.

Henri has moved a little to the right of the previous track at 18-20 kt during the past several hours. However, the cyclone now seems to be moving northward with an initial motion of 355/18 kt. There is no change to the forecast track philosophy. A cut-off low located over the central Appalachians and a ridge building to the east and northeast of Henri should cause the storm to move generally northward tonight. A turn toward the north-northwest and a slower forward speed are expected on Sunday, which should bring the center near or over southern New England or Long Island between 18-24 h. With the more eastward initial position, the forecast track is shifted a bit to the east of the previous forecast. However, there is still some uncertainty of the landfall point, as several of the guidance models are to the left of the official forecast. After landfall, Henri should slow its forward speed and turn eastward as it become steered by the mid-latitude westerlies. Users are reminded to not focus on the exact forecast track, as the average 24-hour track uncertainty is around 40 miles and impacts will extend well away from the center.

Henri is almost out of time to strengthen, as the center will be moving north of the north wall of the Gulf Stream during the next several hours. The intensity forecast will call for modest strengthening during the first 12 h based on the premise that strengthening will occur before Henri reaches the cooler waters. After that, while the cyclone should start to weaken before landfall, it should still be near or at hurricane strength when it reaches southern New England. Rapid weakening is expected after landfall, and Henri is again forecast to become post-tropical in about 48 hours and dissipate in 3 to 4 days.

Key Messages:

  • 1. Dangerous storm surge inundation is expected to begin late tonight or Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Residents in these areas should follow any advice given by local officials.
  • 2. Hurricane conditions are expected to begin late tonight or Sunday in portions of Long Island, Connecticut, and Rhode Island, where a Hurricane Warning is in effect. Tropical storm conditions will begin in these areas late tonight.
  • 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor to isolated moderate river flooding over portions of Long Island, New England, eastern New York and New Jersey.
  • 4. Swells from Henri will continue to affect much of the east coast of the U.S. during the next day or two. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  22/0300Z 38.6N  71.0W   65 KT  75 MPH - Category 1 (ESE Cape May,NJ)
 12H  22/1200Z 40.3N  71.2W   70 KT  80 MPH - Category 1 (ESE Montauk,NY)
 24H  23/0000Z 41.9N  71.8W   55 KT  65 MPH - Tropical Storm (ESE Putnam,CT)
 36H  23/1200Z 43.1N  71.7W   30 KT  35 MPH - Tropical Storm (ENE Weare,NH)
 48H  24/0000Z 43.9N  70.5W   25 KT  30 MPH - Post Tropical (WSW Raymond,ME)
 60H  24/1200Z 44.4N  68.3W   25 KT  30 MPH - Post Tropical (WNW Bar Harbor,ME)
 72H  25/0000Z 44.8N  63.5W   25 KT  30 MPH - Post Tropical (ENE Waverley,NS Canada)
 96H  26/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM EDT Sat Aug 21, 2021

Visible satellite images and microwave data indicate that a tight inner core has formed in association with Henri, but the convective pattern appears ragged in infrared images. An ASCAT pass from earlier today indicated that the 34- and 50-kt winds continue to expand in the southeastern quadrant, and that data was used to update the initial wind radii. The latest Dvorak estimates range from 55 to 77 kt, and based on that data, the initial intensity is held at 65 kt. The NOAA Hurricane Hunters will be investigating Henri this evening.

Henri is moving faster to the north-northeast, or 020 degrees, at 16 kt. There continues to be little change to the forecast track philosophy. A cut-off low located over the central Appalachians and a ridge building to the east and northeast of Henri should cause the storm to continue moving north-northeastward through tonight. A decresae in forward speed and a slight bend to the left is then forecast to occur on Sunday. The latest model guidance has shifted slightly to the right, and the NHC official track forecast has been nudged in that direction. This forecast shows landfall over eastern Long Island and southern Connecticut in about 24 hours. Users are reminded to not focus on the exact forecast track, as the average 24-hour track uncertainty is around 40 miles and impacts will extend well away from the center.

The environment looks favorable for Henri to strengthen through tonight with low shear, upper-level divergence associated with the upper-level trough, and warm SSTs. In fact, SST analyses indicate that Henri will be passing over a patch of very warm 30 deg C waters this evening. By early Sunday Henri is predicted to cross the north wall of the Gulf Stream. That should result in some weakening, but Henri is forecast to be at or near hurricane strength at landfall. Once the center moves inland over the northeast United States, rapid weakening is expected. Henri is forecast to become post-tropical in about 48 hours and dissipate in 3 to 4 days.

Key Messages:

  • 1. Dangerous storm surge inundation is expected to begin late tonight or Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Residents in these areas should follow any advice given by local officials.
  • 2. Hurricane conditions are expected to begin late tonight or Sunday in portions of Long Island, Connecticut, and Rhode Island, where a Hurricane Warning is in effect. Tropical storm conditions will begin in these areas tonight.
  • 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor to isolated moderate river flooding over portions of Long Island, New England, eastern New York and New Jersey.
  • 4. Swells from Henri will continue to affect much of the east coast of the U.S. during the next day or two. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 36.3N  71.4W   65 KT  75 MPH - Category 1 (ESE Virginia Beach,VA)
 12H  22/0600Z 38.8N  71.4W   70 KT  80 MPH - Category 1 (ESE Cape May,NJ)
 24H  22/1800Z 40.8N  72.1W   60 KT  70 MPH - Tropical Storm (ESE Southampton,NY)
 36H  23/0600Z 42.1N  72.4W   40 KT  45 MPH - Tropical Storm (ESE Wilbraham,MA)
 48H  23/1800Z 43.3N  71.9W   25 KT  30 MPH - Tropical Storm (ESE Sutton,NH)
 60H  24/0600Z 43.6N  69.9W   25 KT  30 MPH - Post Tropical (ESE Portland,ME)
 72H  24/1800Z 44.3N  68.1W   25 KT  30 MPH - Post Tropical (ESE Bar Harbor,ME)
 96H  25/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM EDT Sat Aug 21, 2021

The Air Force Reserve and NOAA Hurricane Hunters have been investigating Henri this morning and continue to provide very valuable data. The Air Force aircraft measured a peak flight-level wind of 82 kt at 700 mb, which easily supports hurricane strength, but the initial intensity is set at 65 kt as a blend of these data and somewhat lower SFMR winds. In addition, aircraft data indicate that the minimum pressure has fallen to 991 mb. The NOAA tail Doppler radar data indicate that the storm is becoming more vertically aligned and that a more symmetric eyewall appears to be forming. In addition, dropsonde data from the NOAA Gulfstream IV aircraft flying around Henri indicate that the 34- and 50-kt wind radii are a little larger than previously estimated in the southeastern quadrant. NOAA buoy 41001 located in the northeastern quadrant of the hurricane has recently reported 18 ft. seas.

Henri is moving north-northeastward, or 020 degrees, at 12 kt. The steering pattern appears fairly well established now with a cut off low located over the central Appalachians and a ridge building to the east and northeast of Henri. This pattern should cause the storm to accelerate to the north or north-northeast today followed by a slight bend to the left on Sunday. The latest run of the GFS has shifted to the east, but overall the models are focused in on landfall being between central Long Island and Rhode Island on Sunday. However, users are reminded to not focus on the center itself, as impacts will extend well away from the center, especially to the east. The new NHC track forecast is a little to the east of the previous one and very near the best-performing models, the consensus aids.

The environment looks favorable for Henri to continue to gain strength through tonight with low shear, upper-level divergence associated with the upper-level trough, and warm SSTs. In fact, the GFS and HWRF models show the minimum pressure dropping by 15 mb or more during that time period. By early Sunday, Henri is predicted to cross the north wall of the Gulf Stream and that should cause some weakening, but Henri is forecast to be at or near hurricane strength at landfall. Once the center moves inland over the northeast United States, rapid weakening is expected. Henri is forecast to become post-tropical in 48-60 hours and dissipate in 3 to 4 days.

Key Messages:

  • 1. Dangerous storm surge inundation is expected to begin late tonight or Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Dangerous storm surge is possible beginning late tonight or Sunday in western portions of Long Island and Connecticut in the Storm Surge Watch area. Residents in these areas should follow any advice given by local officials.
  • 2. Hurricane conditions are expected to begin late tonight or Sunday in portions of Long Island, Connecticut, and Rhode Island, where a Hurricane Warning is in effect. Tropical storm conditions will begin in these areas tonight.
  • 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor and isolated moderate river flooding, over portions of Long Island, New England, southeast New York and northern New Jersey.
  • 4. Swells from Henri will continue to affect much of the east coast of the U.S. during the next day or two. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  21/1500Z 34.4N  72.5W   65 KT  75 MPH - Category 1 (ESE Morehead City,NC)
 12H  22/0000Z 36.9N  71.9W   75 KT  85 MPH - Category 1 (ESE Cape Charles,VA)
 24H  22/1200Z 39.7N  71.9W   70 KT  80 MPH - Category 1 (ESE Toms River,NJ)
 36H  23/0000Z 41.3N  72.6W   60 KT  70 MPH - Tropical Storm (ENE Guilford,CT)
 48H  23/1200Z 42.4N  72.9W   35 KT  40 MPH - Tropical Storm (ENE Worthington,MA)
 60H  24/0000Z 43.1N  71.9W   25 KT  30 MPH - Post Tropical (WSW Hillsborough,NH)
 72H  24/1200Z 43.8N  69.2W   25 KT  30 MPH - Post Tropical (ENE Monhegan,ME)
 96H  25/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM EDT Fri Aug 20, 2021 (see 11:00 video below)

Satellite imagery shows that Henri is becoming better organized this evening, with the low-level center becoming more embedded in the convective overcast and an increase in convective banding. There has also been an increase in the anticyclonic outflow. However, reports from Air Force Reserve and NOAA Hurricane Hunter aircraft show that this has not yet resulted in strengthening, as the maximum winds remain about 60 kt to the southeast of the elongated center and the central pressure is in the 994-996 mb range.

Henri has turned northward, and the initial motion is now 010/8. A deep-layer mid-latitude trough over the Appalachians and the Ohio Valley will cut off into a closed low during the next 12-24 h, while a ridge builds northward to the east and northeast of Henri. This evolution should cause the storm to move north-northeastward for 12-24 h, followed by a turn toward the north-northwest from 24-48 h. This motion should bring the center of Henri over the mid-Atlantic states or southern New England between 36-48 h. After 48 h, the cyclone should get caught up in the southern edge of the westerlies and turn generally eastward across southern New England and the Gulf of Maine. There has been little change in the direction of the forecast guidance since the last advisory, but the guidance is faster on this cycle through 48 h. Thus, the new track forecast, which lies close to the consensus models, is faster than the previous forecast through the 48 h point.

A combination of decreasing shear, improved organization, and upper-level divergence associated with the trough to the west should allow Henri to strengthen for the next 24 h or so, and the new intensity forecast calls for a peak intensity of 75 kt. After 24 h, the center should move over cooler water, and weakening should start before landfall in the northeastern United States. However, the cyclone is still expected to be at or near hurricane intensity at landfall. After landfall, Henri should weaken quickly and become post-tropical by the 72 h time. Dissipation is forecast between 96-120 h. The new intensity forecast follows the overall trend of the intensity guidance.

Users are reminded to not focus on the exact forecast of the center of Henri since impacts will extend far from the center.

Key Messages:

  • 1. Dangerous storm surge inundation is expected to begin late Saturday night or Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Dangerous storm surge is possible beginning late Saturday night or Sunday in western portions of Long Island and Connecticut in the Storm Surge Watch area. Residents in these areas should follow any advice given by local officials.
  • 2. Hurricane conditions are expected to begin late Saturday night or Sunday in portions of Long Island and Connecticut, where a Hurricane Warning has been issued. Hurricane conditions are possible late Saturday night or Sunday across portions of Rhode Island and southeastern Massachusetts.
  • 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor and isolated moderate river flooding, over portions of Long Island and New England Sunday into Monday.
  • 4. Swells from Henri will continue to affect much of the east coast of the U.S. through the weekend. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 32.3N  73.5W   60 KT  70 MPH - Tropical Storm (ESE Charleston,SC)
 12H  21/1200Z 34.3N  72.8W   65 KT  75 MPH - Category 1 (ESE Morehead City,NC)
 24H  22/0000Z 37.7N  72.1W   75 KT  85 MPH - Category 1 (ESE Chincoteague,VA)
 36H  22/1200Z 40.2N  72.6W   70 KT  80 MPH - Category 1 (ESE Long Island,NY)
 48H  23/0000Z 41.4N  73.4W   50 KT  60 MPH - Tropical Storm (ENE Bethel,CT)
 60H  23/1200Z 42.2N  73.2W   35 KT  40 MPH - Tropical Storm (ENE Monterey,MA)
 72H  24/0000Z 42.7N  72.3W   30 KT  35 MPH - Post Tropical (ENE Warwick,MA)
 96H  25/0000Z 43.5N  67.0W   25 KT  30 MPH - Post Tropical (WSW Yarmouth,NS Canada)
120H  26/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM EDT Fri Aug 20, 2021

Henri appears to be slowly gaining strength. Deep convection has been increasing during the past few hours and the upper-level outflow continues to become better established on the east side of the circulation. However, the low-level center is still located near the northwestern edge of the deep convection due to ongoing northerly wind shear. An ASCAT-B pass from a few hours ago showed peak winds of around 55 kt, with the strongest winds on the southeast side of the circulation. Based on this data, the initial intensity is set at 60 kt. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Henri again this evening and the data the plane collects will be very helpful in estimating the storm’s strength and structure.

The tropical storm appears to be making the advertised turn to the right, with the latest initial motion estimated to be 335/6 kt. A trough over the central Appalachians is expected to cut off tonight, and the combination of that feature and a building ridge to the east/northeast of Henri should cause the storm to accelerate to the north on Saturday. The latest model runs have generally trended to the left again and are a bit faster, with most showing landfall in about 48 hours. Most of the models now show a slight left turn before landfall as Henri gets caught in the circulation of the aforementioned trough. The latest GFS and ECMWF ensemble members continue to span a region from near New York City to Cape Cod for the landfall point. Based on the latest consensus aids, the official track forecast has again been nudged to the west of the previous one and shows landfall occurring on Sunday. After day 3, Henri is forecast to eject northeastward.

The ongoing northerly shear is expected to decrease tonight, and the global models show a favorable upper-level wind pattern developing over the storm through the weekend. These more conducive atmospheric conditions combined with the warm Gulf Stream waters should allow Henri to strengthen to a hurricane tonight or early Saturday, with additional intensification expected into Saturday night. By early Sunday, however, Henri is forecast to cross the north wall of the Gulf Stream, and that should end its opportunity for strengthening. Although steady to rapid weakening is forecast while Henri moves over cooler waters south of Long Island and New England, it will likely still be at or very near hurricane intensity when it reaches the coast. Post-tropical transition is forecast to occur by day 3 and the system should dissipate in 4 or 5 days.

Users are reminded to not focus on the exact forecast of the center of Henri since impacts will extend far from the center.

Key Messages:

  • 1. Dangerous storm surge inundation is expected to begin Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Warning has been issued. Dangerous storm surge is possible beginning Sunday in western portions of Long Island and Connecticut in the Storm Surge Watch area. Residents in these areas should follow any advice given by local officials.
  • 2. Hurricane conditions are expected to begin Sunday in portions of Long Island and Connecticut, where a Hurricane Warning has been issued. Hurricane conditions are possible Sunday across portions of Rhode Island and southeastern Massachusetts.
  • 3. Heavy rainfall may lead to considerable flash, urban, and small stream flooding, along with the potential for widespread minor and isolated moderate river flooding, over portions of Long Island and New England Sunday into Monday.
  • 4. Swells from Henri will continue to affect much of the east coast of the U.S. through the weekend. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 31.2N  73.9W   60 KT  70 MPH - Tropical Storm (ESE Savannah,GA)
 12H  21/0600Z 32.8N  73.3W   65 KT  75 MPH - Category 1 (ESE Myrtle Beach,SC)
 24H  21/1800Z 35.8N  72.3W   75 KT  85 MPH - Category 1 (ESE Nags Head,NC)
 36H  22/0600Z 38.9N  71.9W   75 KT  85 MPH - Category 1 (ESE Ocean City,NJ)
 48H  22/1800Z 40.8N  72.4W   65 KT  75 MPH - Category 1 (WSW North Sea,NY)
 60H  23/0600Z 42.0N  72.8W   45 KT  50 MPH - Tropical Storm (WSW Southwick,MA)
 72H  23/1800Z 42.9N  72.6W   30 KT  35 MPH - Post Tropical (WSW  Dummerston,VT)
 96H  24/1800Z 43.8N  68.9W   25 KT  30 MPH - Post Tropical (WSW Matinicus,ME)
120H  25/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM EDT Fri Aug 20, 2021 

The Air Force Reserve Hurricane Hunters investigated Henri this morning and based on the flight-level, SFMR, and dropsonde data, the initial intensity is still around 55 kt. The minimum pressure has also been relatively steady. The low-level center of Henri is located close to the northwestern edge of the main area of deep convection, and the vortex is still not vertically aligned due to 20-25 kt of northerly vertical wind shear. Although the intensity of Henri has not changed much during the past couple of days, satellite images show an improving cloud pattern with well- established outflow in the eastern semicircle, which could indicate that Henri is poised to strengthen.

There is some uncertainty in the exact position of Henri given the recent aircraft fixes and the tilt of the vortex, but the initial motion appears to be northwestward at 6 kt. A trough over the central Appalachians is expected to cut off tonight, and the combination of that feature and a building ridge to the east/northeast of Henri should cause the storm to turn northward tonight and accelerate in that direction on Saturday. Some of the models show a slight bend to the west around the time Henri is forecast to make landfall on Sunday, and there remains a fair amount spread in the guidance in where the center of Henri will come ashore. The latest GFS and ECMWF ensemble members span a region from near New York City to Cape Cod for the landfall point. Based on the latest consensus aids and initial position, the official track forecast is nudged to the west of the previous one and shows landfall occurring by late Sunday. After day 3, Henri is forecast to eject northeastward across the Gulf of Maine.

The ongoing northerly shear is expected to decrease later today, and the global models show a favorable upper-level wind pattern developing over the storm later today through the weekend. These more conducive atmospheric conditions combined with the warm Gulf Stream waters should allow Henri to strengthen to a hurricane tonight or early Saturday with additional intensification expected into Saturday night. By early Sunday, however, Henri is forecast to cross the north wall of the Gulf Stream, and that should end its opportunity for strengthening. Although steady to rapid weakening is forecast while Henri moves over cooler waters south of New England, it will likely still be at or very near hurricane intensity when it reaches the coast. Post-tropical transition is forecast to occur in 3 to 4 days, and the new forecast shows Henri dissipated by day 5, in agreement with most of the global models.

Users are reminded to not focus on the exact forecast of the center of Henri since impacts will extend far from the center.

Key Messages:

  • 1. Dangerous storm surge inundation and hurricane conditions are possible beginning Sunday in portions of Long Island, Connecticut, Rhode Island, and southeastern Massachusetts, where a Storm Surge Watch and Hurricane Watch are in effect. Residents in these areas should follow any advice given by local officials.
  • 2. Heavy rainfall may lead to flash, urban, and small stream flooding, along with the potential for widespread minor and isolated moderate river flooding, over portions of southern New England Sunday into Monday.
  • 3. Swells from Henri will begin to reach much of the east coast of the U.S. and Atlantic Canada by the end of the week and continue through the weekend. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 30.4N  73.7W   55 KT  65 MPH - Tropical Storm (ESE Jacksonville,FL)
 12H  21/0000Z 31.5N  73.7W   60 KT  70 MPH - Tropical Storm (ESE Savannah,GA)
 24H  21/1200Z 34.1N  72.7W   70 KT  80 MPH - Category 1 (ESE Wilmington,NC)
 36H  22/0000Z 37.3N  71.8W   75 KT  85 MPH - Category 1 (ESE Cape Charles,VA)
 48H  22/1200Z 39.8N  71.7W   65 KT  75 MPH - Category 1 (ESE New York,NY)
 60H  23/0000Z 41.4N  71.8W   60 KT  70 MPH - Tropical Storm (ENE Westerly,RI)
 72H  23/1200Z 42.4N  71.8W   40 KT  45 MPH - Tropical Storm (ENE Worcester,MA)
 96H  24/1200Z 43.7N  69.4W   35 KT  40 MPH - Post Tropical (WSW Monhegan,ME)
120H  25/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM EDT Thu Aug 19, 2021 

The satellite presentation on Henri this evening continues to exhibit a persistent bursting pattern, with the center estimated to be just to the north and west of the coldest cloud tops which occasionally have been below -80 C in the overshooting tops. This current satellite presentation is primarily due to continued moderate to strong northerly vertical wind shear, which is forcing the convection underneath the cirrus canopy down-shear of the low-level center, as seen on a 2230 UTC SSMIS microwave pass. While the mid-level vortex with the convection also remains tilted down-shear of the low-level center, it has not completely separated due to the persistent convection, preventing the low-level center from escaping poleward in more shallow low-level steering. Tonight’s subjective Dvorak estimates from SAB/TAFB are in agreement with T3.5/55 kt and given that this value is near what the earlier Air Force Reconnaissance mission found, the latest intensity is being maintained at 55 kt for this advisory.

There is a bit of uncertainty determining if Henri has begun a more poleward motion since the center remains under the convective cirrus plume, but my best guess is now 285/9 kt. Over the next 12-24 hours, the mid- to upper-level ridging that has dominated the synoptic steering pattern for Henri the last few days will quickly break down, as a shortwave trough drops in from the Great Lakes into the Mid-Atlantic and cuts off. This feature is now forecast to continue digging in to the west of Henri. To the east, a new mid-level ridge is also forecast to build in to the right of Henri. This synoptic pattern should draw the cyclone poleward with an acceleration to the north-northeast in the 24-48 h period. Afterwards, the aforementioned trough takes on a negative tilt to the southwest of Henri, helping to reorient the mid- to upper-level flow out of the south-southeast, and this flow could result in a slight leftward bend in the track between 48-72 h. The majority of guidance this cycle now is forecasting the mid-level ridge east of Henri to build poleward with the storm, blocking an easy path for the storm to stay on a more northeast heading out to sea. Consequently, the latest NHC forecast track now explicitly shows landfall in southeast Massachusetts at 72 h. The track guidance this cycle has come into better agreement, though there remain some leftward (UKMET) and rightward (ECMWF) outliers. The latest forecast track lies very close to the HFIP corrected consensus approach (HCCA) guidance, which is also very near the latest GFS forecast track.

Data from the NOAA G-IV synoptic mission around Henri shows that just north of the tropical cyclone there remains some very dry mid-latitude air, which is being advected into the storm by 20-25 kt of northerly vertical wind shear. Over the next 24-36 hours, this shear is forecast to gradual subside, as Henri moves near the center of an upper-level ridge axis. By 36-48 hours, the vertical wind shear is forecast to be under 10-kt by both the GFS- and ECWMF-based SHIPS guidance, while the storm is also traversing 28-29 C sea-surface temperatures (SSTs). Thus, the latest NHC intensity forecast still calls for strengthening beginning after 12 hours, and the rate of strengthening could be a bit quicker as the storm moves over the warm gulf stream waters between 36-48 hours. Thereafter, Henri will cross a very sharp SST gradient with sea-surface temperatures down below 23 C near the New England coast to the east of Long Island. Henri is forecast to begin weakening after 48 hours, but the storm could still be near hurricane intensity by the time Henri is forecast to be near the Northeast coastline. Transition to a post-tropical storm is expected to begin shortly thereafter which should be sometime in the 96-h to 120-h points as deep convection ceases over the storm over cold SSTs

As noted previously, the wind field of Henri is expected to expand, especially as it interacts with a mid-latitude trough located to its west. Therefore, users are reminded to not focus on the exact forecast points as impacts will extend far from the center.

Key Messages:

  • 1. Henri is forecast to be near the northeast coast of the U.S. on Sunday and Monday, and the risks of storm surge, wind, and rain impacts in portions of southern New England and eastern Long Island are increasing. Watches will likely be required for portions of this area early Friday.
  • 2. Swells from Henri will begin to reach much of the east coast of the U.S. and Atlantic Canada by the end of the week and continue through the weekend. These swells could cause life-threatening surf and rip currents.
  • 3. Heavy rainfall may lead to flash, urban, and small stream flooding over portions of southeastern New England Sunday into Monday.
FORECAST POSITIONS AND MAX WINDS

INIT  20/0300Z 29.8N  72.3W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 12H  20/1200Z 30.3N  73.2W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 24H  21/0000Z 31.8N  73.3W   60 KT  70 MPH - Tropical Storm (ESE Hilton Head Island,CS)
 36H  21/1200Z 34.4N  72.2W   65 KT  75 MPH - Category 1 (ESE Morehead City,NC)
 48H  22/0000Z 37.6N  71.0W   80 KT  90 MPH - Category 1 (ENE Cape Charles,VA)
 60H  22/1200Z 40.1N  70.6W   75 KT  85 MPH - Category 1 (ESE Montauk,NY)
 72H  23/0000Z 41.7N  70.8W   60 KT  70 MPH - Tropical Storm (WSW Marion, MA)
 96H  24/0000Z 42.5N  70.1W   40 KT  45 MPH - Tropical Storm (ESE Salem,MA)
120H  25/0000Z 43.7N  65.4W   35 KT  40 MPH - Post Tropical (WSW Churchover,NS Canada)

NWS National Hurricane Center Miami FL 500 PM EDT Thu Aug 19, 2021

The Air Force Hurricane Hunters investigated Henri earlier this afternoon and found maximum flight-level winds and SFMR values to support an intensity of about 55 kt and a minimum pressure of 997 mb. The storm’s appearance in satellite images has been generally steady throughout the day with the low-level center located on the northern side of the convective mass, and banding features confined to the south side of the circulation. This somewhat asymmetric cloud pattern is due to about 25 kt of north-northeasterly shear.

The tropical storm is now moving due westward at 9 kt. A mid-level ridge should keep Henri on a westward to west-northwestward track through tonight. On Friday, however, a trough is expected to cut off over the Ohio Valley and mid-Atlantic region of the U.S. while a ridge amplifies to the east of Henri over the western Atlantic. A combination of these features should cause Henri to turn northward on Friday and accelerate in that direction over the weekend. The exact location of the northward turn will be very critical in determining Henri’s future track and how close it gets to New England. The latest GFS run has shifted eastward and the UKMET and ECMWF have shifted westward. Consequently, the net result is very little change in the consensus models and the new NHC track forecast is just a little faster than the previous one. Based on this forecast, Henri is expected to be very near southern New England on Sunday and Monday. The NOAA Gulfstream IV jet will be flying around Henri this evening to help assess the environmental conditions and gather data for the numerical models. It is hoped that these data will help the models more accurately predict the future track of the storm.

Although Henri is a bit weaker now, the overall intensity forecast philosophy has not changed. The shear is expected to persist for another 12 to 24 hours, so little change in strength seems likely during that time period. However, the global models show a more conducive upper-level wind pattern over Henri shortly after that, and in fact, all of the environmental conditions appear favorable for strengthening on Friday and Saturday. Therefore, steady intensification is expected during the 24-60 h time period, and Henri is forecast to become a hurricane during that time. Henri is expected to cross the north wall of the Gulf Stream and move over much cooler SSTs on Sunday, and that should end the opportunity for strengthening and induce a steady weakening trend from days 3 to 5. Post-tropical transition is now shown to occur by the end of the forecast period when Henri is expected to be over SSTs below 20 deg C. It should be noted that as Henri gains latitude and moves near New England, the wind field is expected to expand. Therefore, users are reminded to not focus on the exact forecast points as impacts will extend far from the center.

Key Messages:

  • 1. Henri is forecast to be near the northeast coast of the U.S. on Sunday and Monday, and the risks of storm surge, wind, and rain impacts in portions of southern New England and eastern Long Island are increasing. Watches will likely be required for portions of this area early Friday.
  • 2. Swells from Henri will begin to reach much of the east coast of the U.S. and Atlantic Canada by the end of the week and continue through the weekend. These swells could cause life-threatening surf and rip currents.
  • 3. Heavy rainfall may lead to flash, urban, and small stream flooding over portions of southeastern New England Sunday into Monday.
FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 29.7N  71.4W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 12H  20/0600Z 30.1N  72.6W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 24H  20/1800Z 31.0N  73.2W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 36H  21/0600Z 33.0N  72.6W   65 KT  75 MPH - Category 1 (ESE Myrtle Beach,SC)
 48H  21/1800Z 36.0N  71.3W   75 KT  85 MPH - Category 1 (ESE Nags Head,NC)
 60H  22/0600Z 38.9N  70.3W   80 KT  90 MPH - Category 1 (ESE Atlantic City,NJ)
 72H  22/1800Z 40.8N  70.1W   65 KT  75 MPH - Category 1 (ESE Montauk,NY)
 96H  23/1800Z 42.3N  69.6W   50 KT  60 MPH - Tropical Storm (WNW Provincetown,MA)
120H  24/1800Z 43.6N  65.7W   40 KT  45 MPH - Post Tropical (WNW Oak Park,NS Canada)

NWS National Hurricane Center Miami FL 1100 AM EDT Thu Aug 19, 2021

Henri is not as well organized as it was yesterday. Microwave images show that the vortex is titled to the south with height due to about 25 kt of north-northeasterly wind shear. The system is still producing a fair amount of deep convection, however, and the cloud pattern resembles a central dense overcast with banding features limited to the south side of the circulation. The Dvorak estimates continue to range from 55 kt to 65 kt, and therefore, the initial intensity is again held at 60 kt. The Air Force Reserve Hurricane Hunters will be investigating Henri later today, and the data the aircraft collects will be very helpful in assessing the storm’s structure and strength.

The tropical storm is moving just south of due west at 9 kt. Henri is expected to move generally westward through tonight as the storm remains on the south side of a mid-level ridge. On Friday, however, a trough is expected to cut off over the Ohio Valley and mid-Atlantic region of the U.S. while a ridge amplifies to the east of Henri over the western Atlantic. A combination of these features should cause Henri to turn northward on Friday and accelerate in that direction over the weekend. By early next week, the ridge is expected to weaken, which should cause Henri to turn more toward the east. The models are in much better agreement than they were yesterday and their solutions are clustering around southern New England on Sunday and Monday. The NHC track forecast is just a tad to the left of the previous one and lies near the typically best-performing models, the various consensus aids. In addition to the Air Force aircraft that flies through the storm, the NOAA Gulfstream IV jet will also be flying around Henri later today to help assess the environmental conditions and gather data for the numerical models. It is hoped that these data will help the models more accurately predict the future track of the storm.

The current north-northeasterly shear over Henri is forecast to continue for about another day, and given the degraded structure of the system it seems unlikely that the storm will strengthen during that time period. However, the shear is expected to decrease on Friday and it will remain quite low through the weekend. Therefore, strengthening to a hurricane is expected during that time period. Once Henri crosses the north wall of the Gulf Stream in a few days, steady weakening is predicted. The NHC intensity forecast is just an update of the previous one and lies near the middle of the guidance envelope.

It should be noted that as Henri gains latitude and moves near New England, the wind field is expected to expand. Therefore, users are reminded to not focus on the exact forecast points as impacts will extend far from the center.

Key Messages:

  • 1. Henri is forecast to be near the northeast coast of the U.S. on Sunday and Monday, and the risks of storm surge, wind, and rain impacts in portions of southern New England and eastern Long Island are increasing. Watches will likely be required for portions of this area on Friday.
  • 2. Swells from Henri will begin to reach much of the east coast of the U.S. and Atlantic Canada by the end of the week and continue through the weekend. These swells could cause life-threatening surf and rip currents.
ORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z 29.5N  70.5W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 12H  20/0000Z 29.7N  71.9W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 24H  20/1200Z 30.4N  72.9W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 36H  21/0000Z 31.9N  72.9W   65 KT  75 MPH - Category 1 (ESE Charleston,SC)
 48H  21/1200Z 34.4N  72.0W   75 KT  85 MPH - Category 1 (ESE Morehead City,NC)
 60H  22/0000Z 37.3N  70.7W   80 KT  90 MPH - Category 1 (ESE Ocean City,MD)
 72H  22/1200Z 39.6N  70.0W   75 KT  85 MPH - Category 1 (ESE New York,NY)
 96H  23/1200Z 41.6N  69.7W   55 KT  65 MPH - Tropical Storm (ESE Chatham,MA)

NWS National Hurricane Center Miami FL 1100 PM AST Wed Aug 18, 2021 

Henris appearance this evening is one of a tropical cyclone that is battling vertical wind shear. The satellite structure has evolved into a large convective plume with overshooting cold -70 to -75 C cloud top temperatures near the center of the convective mass. Underneath the cirrus, Henris structure has remained steady-state, with a SSMIS pass at 2243Z showing a ragged mid-level eye on the 91 GHz channel that remains displaced a bit southeast of the low-level signature on 37 GHz. The latest satellite intensity estimates have a large spread in values ranging from 55-kt up to 80-kt. I have elected to maintain Henris intensity at 60 kt for this advisory, but there is a larger than normal uncertainty in this estimate.

The initial motion continues to be just south of due west at 265/8 kt. The short-term track guidance is in general agreement that Henri will continue a general westward motion for the next day or so, as the cyclone is caught to the south of a pronounced mid- to upper-level ridge. However, the models disagree on how far westward Henri is able to advance in the short-term, and these track differences appear to be related to Henri’s intensity and vertical depth of the circulation. This track dependency is nicely illustrated by the most recent ECMWF ensemble guidance, where stronger members move further south and west in the short-term, ending up on the left-side of the ensemble mean, while weaker members move slower and more poleward. The deterministic guidance is similar, with the weaker ECMWF and Canadian runs off to the east/right while the stronger GFS and UKMET runs are further left/west.

These short-term track differences appear pivotal, because the ridge over Henri is then expected to quickly erode as a mid-latitude trough digs in over the Ohio Valley and becomes negatively tilted over the Mid-Atlantic. The leftward track guidance has Henri interacting with this trough leading to a track forecast much closer to the northeastern US, while the rightward track guidance is not captured by this feature, and stay further offshore escaping out to sea. In general, the mean of the track guidance is very similar, or just a shade to the right of the previous cycle. I have elected to maintain a very similar track to the previous advisory, splitting the difference between the previous forecast just left, and the reliable HCCA consensus aid just right. As mentioned previously, a NOAA Gulfstream IV aircraft has been scheduled to investigate the synoptic environment of Henri tomorrow and will hopefully provide more data ingested into the model guidance to reduce the large track spread seen in the current cycle.

Henri is now under moderate northerly shear that is forecast to increase to 25-30 knots over the next 24 hours. While this would ordinarily weaken the tropical cyclone, the system also remains under very warm 29-30 C sea-surface temperatures that are somewhat above normal for this time of year. Due to these offsetting factors, the latest NHC intensity forecast maintains Henri at 60-kt for the next 24 hours. Afterwards, the shear is forecast to decrease as the storm turns more poleward directly under the upper-level ridge axis. This favorable synoptic pattern should allow Henri to intensify and gradual intensification is shown up to a 80-kt peak in 72-h. The NHC intensity forecast is more or less in the mean of the large guidance spread, though it should be noted that the regional hurricane models (HWRF, HMON, COAMPS-TC) have somewhat stronger peak intensities later in the forecast period.

Key Messages:

  • 1. The forecast track of Henri remains near the northeast coast of the U.S. this weekend and early next week, and the risks of storm surge, wind, and rain impacts in portions of the northeastern U.S. and Atlantic Canada remains a distinct possibility. Interests in these areas should closely follow the progress of Henri and check for updates to the forecast.
  • 2. Swells from Henri will begin to reach much of the east coast of the U.S. and Atlantic Canada by the end of the week and continue through the weekend. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  19/0300Z 29.8N  68.5W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 12H  19/1200Z 29.8N  69.9W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 24H  20/0000Z 30.0N  71.8W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 36H  20/1200Z 30.7N  72.7W   65 KT  75 MPH - Category 1 (ESE St. George's,Bermuda)
 48H  21/0000Z 32.3N  72.8W   70 KT  80 MPH - Category 1 (ENE Charleston,SC)
 60H  21/1200Z 34.4N  71.8W   75 KT  85 MPH - Category 1 (ESE Morehead City,NC)
 72H  22/0000Z 36.9N  70.7W   80 KT  90 MPH - Category 1 (ENE Virginia Beach,VA)
 96H  23/0000Z 40.4N  69.4W   70 KT  80 MPH - Category 1 (ESE New York,NY)
120H  24/0000Z 41.8N  68.3W   60 KT  70 MPH - Tropical Storm (ESE Provincetown,MA)

NWS National Hurricane Center Miami FL 500 PM AST Wed Aug 18, 2021 

Henri appears a little better organized this afternoon. The storm still has a central dense overcast pattern and there have been hints of an eye evident in visible satellite images. Microwave images continue to show a mid-level eye feature, but the storm does not appear quite as well organized in the low-levels, and the vortex is still titled southward with height. The latest Dvorak estimates range from 55 to 67 kt, and based on that data the initial intensity is nudged up to 60 kt, just below hurricane strength.

Henri is moving just south of due west at a slightly faster pace now, 265/8 kt. The storm is expected to continue westward for another 36 hours or so as it moves in the flow on the south side of a mid-level ridge. A gradual turn to the north is forecast to begin on Friday when a cutoff low forms over the Ohio Valley and the northeastern U.S. This general northward motion should continue through the weekend as another ridge builds to the east of Henri over the northwestern Atlantic. The models continue their westward shift, and the NHC track forecast has again been adjusted in that direction and no longer shows a northeastward motion out to sea. In particular, the westward adjustment at day 5 was a sizable 150 miles, and even with this shift the NHC forecast is still a little to the east of some of the consensus aids. NOAA Gulfstream IV missions and special weather balloon soundings have been scheduled, and it is hoped that this additional data will help the models handle the evolving steering pattern. Given the uncertainty in the longer range track forecast, users should be prepared for additional adjustments to the NHC track prediction in future forecast cycles.

The storm is currently in an environment of about 15-20 kt of northerly wind shear according to the SHIPS model and analyses from CIMSS at the University of Wisconsin, which is the reason the vortex is currently titled. The shear should persist for another day or so, and little change in strength seems likely during that time period. However, strengthening is expected on Friday and Saturday as the shear decreases while the storm remains over the Gulf Stream. Some weakening seems likely at days 4 and 5 when the storm is expected to be over cooler waters. The NHC intensity forecast lies roughly near the middle of the guidance envelope and only minor changes were made to the previous prediction.

Key Messages:

  • 1. The forecast track of Henri has shifted toward the northeast coast of the U.S. this weekend and early next week, increasing the risk of direct storm surge, wind, and rain impacts in portions of the northeastern U.S. and Atlantic Canada during that time. Interests in these areas should closely follow the progress of Henri and check for updates to the forecast.
  • 2. Swells from Henri will begin to reach much of the east coast of the U.S. and Atlantic Canada by the end of the week and continue through the weekend. These swells could cause life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS

INIT  18/2100Z 29.9N  67.6W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 12H  19/0600Z 29.8N  69.0W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 24H  19/1800Z 29.8N  70.7W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 36H  20/0600Z 30.1N  72.3W   65 KT  75 MPH - Category 1 (ESE St. George's,Bermuda)
 48H  20/1800Z 31.0N  73.2W   70 KT  80 MPH - Category 1 (ESE Savannah,GA)
 60H  21/0600Z 32.7N  72.7W   75 KT  85 MPH - Category 1 (WSW Murrells Inlet.SC)
 72H  21/1800Z 35.2N  71.7W   80 KT  90 MPH - Category 1 (ESE Nags Head,NC)
 96H  22/1800Z 39.3N  70.0W   70 KT  80 MPH - Category 1 (ESE Atlantic City,NJ)
120H  23/1800Z 41.4N  69.8W   60 KT  70 MPH - Tropical Storm (ENE Nantucket,MA)

NWS National Hurricane Center Miami FL 1100 AM AST Wed Aug 18, 2021

Deep convection has been increasing during the past several hours in association with Henri, and the cloud pattern mostly consists of a central dense overcast with some fragmented bands around it. The Dvorak estimates are steady at 3.5/55 kt from TAFB and SAB, and therefore, the initial intensity is held at that value. However, the latest automated Dvorak values from CIMSS at the University of Wisconsin are higher, so it is possible that Henri could be slightly stronger. An SSMIS pass from 1124 UTC showed some southward tilt of the vortex with height and revealed a small mid-level eye feature.

Henri continues to move just south of due west at 7 kt. The storm is expected to move westward during the next day or so as it moves in the flow on the south or southeast side of a mid-level ridge. This ridge is expected to slide eastward by Friday as a mid- to upper-level low develops over the Ohio Valley and northeastern U.S. In response, Henri is expected to turn northward or north- northeastward on Friday and continue in that direction through the weekend. One complicating factor is that several of the models show a ridge building over the northwestern Atlantic and Atlantic Canada, which could cause the storm to stay on a more northward track closer to New England than currently forecast. The spread in the models for Henri’s future track is quite large, with some guidance as far west as Long Island and as far east as 62W longitude. Overall, the models continue to walk left each cycle, and the NHC track forecast has again been shifted in that direction. NOAA Gulfstream IV missions and special weather balloon soundings have been scheduled, and it is hoped that this additional data will help the models handle the evolving steering pattern. Given the uncertainty in the longer range track forecasts, users should be prepared for additional adjustments to the NHC track forecast in future forecast cycles.

The storm is currently in an environment of about 15-20 kt of northerly wind shear according to the SHIPS model and analyses from CIMSS at the University of Wisconsin. Since the shear is expected to persist or become a little stronger during the next couple of days, little change in strength is predicted during that time period. After that time, the shear is expected to lessen and that should allow Henri to strengthen to a hurricane by the weekend. Some weakening is shown by the end of the period when Henri is forecast to be moving over cooler waters. The NHC intensity forecast is largely an update of the previous one and is just a little lower than the consensus aids.

Key Messages:

  • 1. Swells from Henri could reach much of the east coast of the U.S. and Atlantic Canada by the end of the week and continue through the weekend. These swells could cause life-threatening surf and rip currents.
  • 2. Uncertainty in the track forecast for Henri this weekend and early next week is larger than usual, and there is some risk of direct impacts from Henri in portions of the northeastern U.S. and Atlantic Canada during that time. Interests in these areas should follow updates to the forecast through the next several days.
FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 30.0N  66.6W   55 KT  65 MPH - Tropical Storm (EWE St. George's,Bermuda)
 12H  19/0000Z 29.9N  67.9W   60 KT  70 MPH - Tropical Storm (EWE St. George's,Bermuda)
 24H  19/1200Z 29.8N  69.8W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 36H  20/0000Z 30.1N  71.4W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 48H  20/1200Z 30.7N  72.4W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 60H  21/0000Z 32.1N  72.5W   65 KT  75 MPH - Category 1 (ESE Charleston,SC)
 72H  21/1200Z 34.2N  71.5W   75 KT  85 MPH - Category 1 (ESE Wilmington.NC)
 96H  22/1200Z 38.0N  69.6W   75 KT  85 MPH - Category 1 (ESE Ocean City,MD)
120H  23/1200Z 41.0N  67.0W   65 KT  75 MPH - Category 1 (ENE New York,NY)

NWS National Hurricane Center Miami FL 1100 PM AST Tue Aug 17, 2021 

Henri’s appearance on satellite imagery has remained more or less steady-state, featuring a small CDO with additional convective banding along the eastern side of the circulation. However, the earlier mid-level eye feature that was trying to develop on radar from Bermuda has recently become more ill-defined, possibly due to some dry-air being entrained into the inner-core of the storm. The latest Dvorak subjective estimates from SAB and TAFB were T3.0/45 kt and T3.5/55 kt, respectively. In addition, a 2336 UTC ASCAT-A pass had lower peak wind retrievals than what was found earlier today, but this instrument may not be quite able to sample the relatively small tropical cyclone core observed on radar. For now, the initial intensity will be held at 55 kt, though this estimate could be a bit generous given the recent scatterometer data.

Henri has begun a more pronounced motion to the west-southwest, and the latest initial motion is estimated at 255/08 kt. An amplified mid- to upper-tropospheric ridge located northwest of Henri is expected to keep the storm on a west-southwestward or westward heading in the short term. However this ridge will begin to gradually erode as an mid- to upper-level trough propagates eastward to the Eastern United States. This should allow Henri to start gaining latitude by 48 hours, turning toward the northwest, north, and then northeast as the mid-level ridging redevelops southeast of the cyclone. There remains a large amount of spread in the guidance, with the stronger regional hurricane models on the left side, while the weaker global models remain more on the right side of the guidance envelope. In general though, there was another westward shift in the guidance suite, so the latest NHC forecast track was adjusted again in that direction, and is in closest agreement to the HCCA guidance aid.

The intensity forecast in the short-term is tricky. Last night and this morning, Henri’s deep convection was been able to propagate into its up-shear quadrant, in spite of light to moderate northwesterly shear importing fairly dry mid-latitude air from the north. Consequently, the storm has been able to intensify and become more axis-symmetrical. Over the past few hours, however, the convection to the northwest of the center has eroded once again on Bermuda radar, likely due to dry air entrainment by the aforementioned vertical wind shear. On the other hand, the tropical cyclone is currently over sea-surface temperatures above 29 C, which will likely allow for significant boundary layer recovery of dry mid-level air that is able to get into the inner core. Thus, even as northerly vertical wind shear increases over the next 24 hours, Henri is expected to maintain its intensity. After 60 hours, this northerly shear is expected to subside, and Henri will have an opportunity to intensify towards the end of the forecast. The latest NHC intensity forecast is quite similar to the previous one for the first 60 hours, but is a little stronger in the latter time periods, blending the reliable HCCA guidance with the more aggressive regional hurricane models (HWRF, COAMPS-TC).

FORECAST POSITIONS AND MAX WINDS

INIT  18/0300Z 30.0N  65.1W   55 KT  65 MPH - Tropical Storm (ESE St. George's,Bermuda)
 12H  18/1200Z 29.9N  66.0W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 24H  19/0000Z 29.8N  67.7W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 36H  19/1200Z 29.8N  69.5W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 48H  20/0000Z 30.1N  71.1W   60 KT  70 MPH - Tropical Storm (ESE St. George's,Bermuda)
 60H  20/1200Z 30.9N  72.0W   60 KT  70 MPH - Tropical Storm (ESE Jacksonville,FL)
 72H  21/0000Z 32.0N  71.9W   70 KT  80 MPH - Category 1 (ESE Charleston,SC)
 96H  22/0000Z 36.6N  69.4W   80 KT  90 MPH - Category 1 (ESE Virginia Beach,VA)
120H  23/0000Z 40.2N  65.0W   80 KT  90 MPH - Category 1 (ESE New York,NY)

NWS National Hurricane Center Miami FL 500 PM AST Tue Aug 17, 2021

Henri appears to be gaining strength. Satellite images show banding features becoming increasingly curved, especially on the east side of the system, and an eye feature has been occasionally seen in radar images from Bermuda. The upper-level outflow is also well established to the north and east of the center. The center itself is estimated to be located near the western edge of the convection, but it is possible that a new center is forming farther east. The initial intensity is raised to 55 kt following the Dvorak classification from TAFB. The initial wind radii has been expanded outward based on an earlier ASCAT pass.

The tropical storm appears to have slowed down, and the latest initial motion estimate is 255/2 kt. A subtropical ridge over the western Atlantic is building eastward to the north of Henri, and this feature should steer the storm westward at a slightly faster pace during the next two to three days. After that time, the ridge is expected to weaken and shift farther east as a cut off low or negatively-tilted trough develops over the northeast U.S. This change in the steering pattern should cause Henri to turn northeastward between Bermuda and the east coast of the U.S in the 72-120 h period. There is a fair amount of spread in exactly when and where Henri makes this turn and the GFS and EC ensembles have some members not far offshore of New England and Atlantic Canada. Overall, the guidance has shifted westward again this cycle, and the NHC track forecast has been adjusted accordingly from days 3 to 5.

The northwesterly shear currently affecting Henri is subsiding, which should allow the storm to gain a little more strength tonight. However, a round of moderate northerly shear is expected to setup over Henri on Wednesday and Thursday and that will likely temporarily end the opportunity for strengthening. Although this shear would typically cause some weakening, the combination of warm SSTs and increasing mid-level moisture could offset the negative influences of the shear. By Friday and over the weekend, the shear is expected to lessen again and since the other environmental factors are predicted to remain favorable for the storm, strengthening is shown from days 3-5. This forecast is above the previous one, and lies fairly close to the middle of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  17/2100Z 30.4N  64.2W   55 KT  65 MPH - Tropical Storm (ESE St. George's,Bermuda)
 12H  18/0600Z 30.3N  65.5W   60 KT  70 MPH - Tropical Storm (WSW St. George's,Bermuda)
 24H  18/1800Z 30.2N  67.0W   60 KT  70 MPH - Tropical Storm (WSW St. George's,Bermuda)
 36H  19/0600Z 30.2N  68.6W   60 KT  70 MPH - Tropical Storm (WSW St. George's,Bermuda)
 48H  19/1800Z 30.3N  70.0W   60 KT  70 MPH - Tropical Storm (WSW St. George's,Bermuda)
 60H  20/0600Z 31.0N  71.1W   60 KT  70 MPH - Tropical Storm (WSW St. George's,Bermuda)
 72H  20/1800Z 32.0N  71.5W   65 KT  75 MPH - Category 1 (WSW St. George's,Bermuda)
 96H  21/1800Z 35.5N  69.6W   70 KT  80 MPH - Category 1 (ESE Nags Head,NC)
120H  22/1800Z 39.1N  65.2W   70 KT  80 MPH - Category 1 (ESE Atlantic City,NJ)

NWS National Hurricane Center Miami FL 1100 AM AST Tue Aug 17, 2021 

Henri remains a sheared tropical storm. Geostationary satellite images and microwave data show a relatively large area of deep convection (~200 miles across), but the center of the storm is located near the western edge of the thunderstorms due to ongoing northwesterly vertical wind shear. The latest Dvorak estimates have been steady at 3.0/45 kt from TAFB and SAB, and based on that data, the initial intensity is held at 45 kt. The center of Henri is located roughly 130 miles south-southeast of Bermuda currently, and this will likely be as close as the storm gets to the island.

The tropical storm is gradually turning to the west, as expected, and the initial motion is estimated to be 255/5 kt. A subtropical ridge over the western Atlantic is building eastward to the north of Henri, and this feature should steer the storm westward at a slightly faster pace during the next two or three days. After that time, the ridge is expected to weaken and shift farther east as a cut off low or negatively-tilted trough develops over the northeast U.S. This change in the steering pattern should cause Henri to turn northeastward between Bermuda and the east coast of the U.S in the 72-120 h period. The NHC track forecast is a little faster than the previous one in the short term and farther west than the previous one from days 3-5, trending toward the latest consensus models.

The northwesterly shear currently affecting Henri is expected to subside later today, and that should allow the storm to gain strength during the next 12-24 hours. However, a round of moderate northerly shear is expected to setup over Henri during the 24-96 hour period. Although this shear would typically cause some weakening, the combination of warm SSTs and increasing mid-level moisture could offset the negative influences of the shear. Therefore, no change in strength is predicted beyond the 24 h period. Some of the models suggest that the shear could lessen again this weekend, so although not explicitly forecast, some strengthening is possible then.

FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 30.4N  64.3W   45 KT  50 MPH - Tropical Storm (ESE St. George's,Bermuda)
 12H  18/0000Z 30.4N  65.1W   50 KT  60 MPH - Tropical Storm (WSW St. George's,Bermuda)
 24H  18/1200Z 30.3N  66.5W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 36H  19/0000Z 30.3N  68.2W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 48H  19/1200Z 30.4N  69.7W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 60H  20/0000Z 30.7N  70.6W   55 KT  65 MPH - Tropical Storm (ESE Jacksonville,FL)
 72H  20/1200Z 31.6N  71.3W   55 KT  65 MPH - Tropical Storm (ESE Savannah,GA)
 96H  21/1200Z 34.1N  69.6W   55 KT  65 MPH - Tropical Storm (ESE Myrtle Beach,SC)
120H  22/1200Z 37.4N  66.0W   55 KT  65 MPH - Tropical Storm (ESE Cape Charles,VA)

NWS National Hurricane Center Miami FL 1100 PM AST Mon Aug 16, 2021 

Bursts of deep convection continue to pulse over the southeastern portion of Henri’s circulation. Although the tropical cyclone is still being affected by dry-air entrainment and light-to-moderate shear, the latest subjective and objective satellite intensity estimates are a little higher than before, and a blend of those estimates yields an initial wind speed of 40 kt for this advisory. Henri is forecast to remain over SSTs of 28-29C throughout the forecast period, but the mid-level relative humidity is forecast to remain fairly dry, which is likely to only support gradual strengthening over the next day or so. After that time, a significant increase in northeasterly shear is anticipated, and that is likely to stop further strengthening. As mentioned in the previous advisory, given the small size of Henri, the tropical cyclone is likely to be more susceptible to this shear and it is possible that Henri weakens more than indicated below by day 3. The NHC intensity forecast is a blend of the various statistical aids, and the CTCI and HMNI models. Less weight is again placed on the HWRF model, which remains quite aggressive in strengthening Henri over the next several days despite the expected increase in shear and dry mid-level environment.

Henri is moving southwestward or 215/4 kt. The tropical storm is forecast to move in a counterclockwise motion over the next several days as it moves around a mid-tropospheric high that is forecast to shift eastward over the western Atlantic. This motion should take Henri south of Bermuda late Tuesday or Tuesday night. By 72 hours, the storm is expected to reach the western extent of the ridge and turn northward, and then northeastward by the end of the forecast period. There is still some spread in the guidance as to when and how sharp the turn will be. As a result, the NHC track forecast is a blend of the typically reliable GFS and ECMWF models later in the period.

FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 30.7N  63.3W   40 KT  45 MPH - Tropical Storm (ENE St. George's,Bermuda)
 12H  17/1200Z 30.5N  63.8W   45 KT  50 MPH - Tropical Storm (ENE St. George's,Bermuda)
 24H  18/0000Z 30.4N  64.8W   50 KT  60 MPH - Tropical Storm (ENE St. George's,Bermuda)
 36H  18/1200Z 30.3N  66.2W   50 KT  60 MPH - Tropical Storm (ENE St. George's,Bermuda)
 48H  19/0000Z 30.3N  67.8W   50 KT  60 MPH - Tropical Storm (ENE St. George's,Bermuda)
 60H  19/1200Z 30.5N  69.3W   50 KT  60 MPH - Tropical Storm (WSW St. George's,Bermuda)
 72H  20/0000Z 31.3N  70.1W   45 KT  50 MPH - Tropical Storm (WSW St. George's,Bermuda)
 96H  21/0000Z 32.8N  69.7W   45 KT  50 MPH - Tropical Storm (WSW St. George's,Bermuda)
120H  22/0000Z 35.0N  66.5W   45 KT  50 MPH - Tropical Storm (WSW St. George's,Bermuda)

NWS National Hurricane Center Miami FL 500 PM AST Mon Aug 16, 2021 

Deep convection has persisted near and southeast of the center of the small tropical cyclone today, and subjective Dvorak intensity estimates were a consensus T2.5 (35 kt) at 1800 UTC. Objective estimates from ADT and SATCON also support tropical storm status, therefore the depression has been upgraded to a 35-kt tropical storm with this advisory. Henri (ahn-REE) becomes the eighth named storm of the 2021 Atlantic hurricane season. This is the fourth-earliest eighth storm on record with only 2020, 2005, and 1936 having the eighth-named storm form earlier in the season.

Henri is located over warm waters, but is currently being affected by light to moderate northerly shear and dry mid-level air in the surrounding environment. Although these conditions are not overly conducive for strengthening, most of the intensity guidance supports gradual intensification over the next 24 to 48 hours. After that time, a significant increase in northeasterly upper-level winds is depicted by the global models over the system, which is likely to halt further strengthening. In fact, given the small size of Henri, it is likely to be more susceptible to the increase in shear, and it could weaken faster than indicated below. The HWRF remains more aggressive, but given the expected increase in shear, that solution still does not seem likely. The NHC intensity forecast is in best agreement with the LGEM model, and is slightly below the IVCN intensity consensus.

The tropical storm is moving south-southwestward or 200/6 kt. Henri is forecast to move west-southwestward during the next 12-24 hours around the southeastern side of a mid-tropospheric high over the western Atlantic. After that time, Henri should turn westward as the ridge shifts eastward to the north of the tropical cyclone, and after 72 hours Henri is expected to approach the western extent of the ridge and should turn northward and then north-northeastward. The dynamical model guidance is in somewhat better agreement during the next 48-72 hours, but there remains some spread later in the period as to how sharp of northward turn occurs. The new NHC track forecast is similar to the previous advisory and lies near the center of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  16/2100Z 31.0N  62.9W   35 KT  40 MPH - Tropical Storm (ENE St. George's,Bermuda)
 12H  17/0600Z 30.5N  63.4W   40 KT  45 MPH - Tropical Storm (ENE St. George's,Bermuda)
 24H  17/1800Z 30.3N  64.2W   45 KT  50 MPH - Tropical Storm (ENE St. George's,Bermuda)
 36H  18/0600Z 30.2N  65.4W   50 KT  60 MPH - Tropical Storm (ENE St. George's,Bermuda)
 48H  18/1800Z 30.2N  66.9W   50 KT  60 MPH - Tropical Storm (ENE St. George's,Bermuda)
 60H  19/0600Z 30.3N  68.5W   50 KT  60 MPH - Tropical Storm (WSW St. George's,Bermuda)
 72H  19/1800Z 30.5N  69.9W   45 KT  50 MPH - Tropical Storm (WSW St. George's,Bermuda)
 96H  20/1800Z 31.8N  70.2W   45 KT  50 MPH - Tropical Storm (WSW St. George's,Bermuda)
120H  21/1800Z 34.2N  68.4W   45 KT  50 MPH - Tropical Storm (WSW St. George's,Bermuda)

NWS National Hurricane Center Miami FL 1100 AM AST Mon Aug 16, 2021

Although the center of the depression is embedded beneath deep convection, Dvorak estimates from TAFB and SAB are not a consensus T2.5 quite yet. Therefore, the depression is still estimated to be producing maximum winds of 30 kt. Very warm waters and low to moderate deep-layer shear are expected to support strengthening during the next couple of days. After 48 hours, strong northerly to northeasterly shear of 25-30 kt is likely halt any intensification. For the most part, the NHC intensity forecast is very close to the tightly clustered SHIPS, LGEM, HCCA, and IVCN aids. As we’ve seen in several cases this year, the HWRF is a notable high outlier, bringing the system to category 2 hurricane strength in 2-3 days. Given the expected shear, that solution does not appear likely at this point.

The depression has been moving southward, or 185/8 kt, and it is expected to rotate around a mid-tropospheric high located over the western Atlantic. Track models are in general agreement that the system will make a clockwise loop in the coming days, with most of the disagreement being in how sharp the turn will be. In part due to the system’s initial motion, the updated NHC track forecast now shows a wider, sweeping loop and is close to the TVCA consensus aid. It should be noted that the ECMWF and HCCA aids are even farther south and show an even more gradual turn.

FORECAST POSITIONS AND MAX WINDS

INIT  16/1500Z 31.3N  62.8W   30 KT  35 MPH - Depression (ENE St. George's,Bermuda)
 12H  17/0000Z 30.6N  63.1W   35 KT  40 MPH - Tropical Storm (ENE St. George's,Bermuda)
 24H  17/1200Z 30.2N  63.8W   40 KT  45 MPH - Tropical Storm (ENE St. George's,Bermuda)
 36H  18/0000Z 29.9N  64.7W   45 KT  50 MPH - Tropical Storm (ENE St. George's,Bermuda)
 48H  18/1200Z 29.8N  66.0W   50 KT  60 MPH - Tropical Storm (WSW St. George's,Bermuda)
 60H  19/0000Z 29.9N  67.4W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 72H  19/1200Z 30.1N  68.7W   50 KT  60 MPH - Tropical Storm (WSW St. George's,Bermuda)
 96H  20/1200Z 31.0N  70.1W   45 KT  50 MPH - Tropical Storm (WSW St. George's,Bermuda)
120H  21/1200Z 33.1N  69.2W   45 KT  50 MPH - Tropical Storm (WSW St. George's,Bermuda)

NWS National Hurricane Center Miami FL 1100 PM AST Sun Aug 15, 2021 

A small well-defined low-pressure system located just east-northeast of Bermuda has produced persistent deep convection since this morning. Radar imagery from Bermuda along with geostationary and polar orbiting microwave satellite data show that the convection is sufficiently well organized to meet the definition for a tropical cyclone. Therefore advisories have been started on Tropical Depression Eight. The initial intensity is set at 25 kt, based on believable winds near that value in a pair of recent ASCAT overpasses. Dvorak estimates from TAFB and SAB were a little higher, so this estimate could be slightly conservative.

Confidence in the forecast is reasonably high for the next 48 to 72 h. The depression should make a slow clockwise turn around Bermuda, steered by a mid-level ridge currently centered off the coast of the Carolinas. Warm SSTs should provide ample fuel to support at least slight strengthening during this period, despite expected northerly shear, and this is shown by all of the intensity guidance. The NHC forecast is very near the multi-model consensus for both track and intensity through that period.

Beyond 72 h, the track and intensity models diverge quickly. The HWRF and COAMPS-TC models rapidly intensify the system to major hurricane strength. A stronger, deeper vortex would likely be steered generally westward through the end of the forecast period, influenced by a deeper-layer steering flow. However, the global models have a much weaker, shallower system which turns northward, and then possibly accelerates northeastward by day 5. As a result, the spread in the track guidance is nearly 800 n mi by day 5, with the GFS and HWRF taking the extreme positions to the northeast and southwest, respectively. The official track forecast takes a middle approach, and is between the various consensus aids at days 4 and 5. The NHC intensity forecast is slightly more conservative, and is below the consensus at the end of the period. Significant changes to the forecast may be required in subsequent advisory packages.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0300Z 33.2N  62.7W   25 KT  30 MPH - Depression (ENE St. George's,Bermuda)
 12H  16/1200Z 32.4N  62.8W   30 KT  35 MPH - Depression (ENE St. George's,Bermuda)
 24H  17/0000Z 31.5N  63.3W   35 KT  40 MPH - Tropical Storm (ENE St. George's,Bermuda)
 36H  17/1200Z 31.1N  64.0W   40 KT  45 MPH - Tropical Storm (ENE St. George's,Bermuda)
 48H  18/0000Z 31.0N  64.9W   45 KT  50 MPH - Tropical Storm (ENE St. George's,Bermuda)
 60H  18/1200Z 31.0N  66.1W   50 KT  60 MPH - Tropical Storm (WSW St. George's,Bermuda)
 72H  19/0000Z 31.2N  67.4W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
 96H  20/0000Z 32.0N  68.5W   55 KT  65 MPH - Tropical Storm (WSW St. George's,Bermuda)
120H  21/0000Z 33.5N  68.0W   55 KT  65 MPH - Tropical Storm (WNW St. George's,Bermuda)

NWS National Hurricane Center Miami FL 800 PM EDT Sun Aug 15, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Fred, located over the east-central Gulf of Mexico, and on Tropical Depression Grace, located about 100 miles south-southeast of the Dominican Republic.

  • 1. Satellite imagery and radar data from Bermuda indicate that showers and thunderstorms associated with a small but well-defined area of low pressure located northeast of Bermuda have continued to become better organized during the past few hours. If this trend continues, advisories will likely be initiated on a new tropical depression later tonight. The system is forecast to move slowly toward the south or southwest during the next day or so, and then turn westward on Tuesday, passing near or just east and south of Bermuda. Interests in Bermuda should monitor the progress of this system, and a Tropical Storm Watch could be required for that island tonight. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Sun Aug 15, 2021

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

The National Hurricane Center is issuing advisories on recently re-designated Tropical Storm Fred, located over the east-central Gulf of Mexico, and on Tropical Storm Grace, located over the northeastern Caribbean Sea just to the south of Puerto Rico.

  • 1. A small but well-defined low pressure system located about 175 miles northeast of Bermuda continues to produce disorganized shower and thunderstorm activity. Environmental conditions appear conducive for some development of this low during the next couple of days, and a tropical depression could form while it moves slowly to the south or south-southwest at about 5 mph, near or to the east of Bermuda. By Tuesday, upper-level winds are forecast to become less conducive for tropical cyclone formation. Interests in Bermuda should monitor the progress of this system during the next few days. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Sun Aug 15, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Grace, located over the northeastern Caribbean Sea just to the south-southeast of Puerto Rico. The National Hurricane Center is issuing advisories on the Remnants of Fred, which are expected to regenerate into a tropical cyclone over the eastern or central Gulf of Mexico later today. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.

  • 1. A small but well-defined low pressure system located about 200 miles north-northeast of Bermuda is producing disorganized showers and thunderstorms mainly to the south of the center. Some gradual development is possible over the next couple of days while the system moves slowly to the south or south-southwest at about 5 mph, near or to the east of Bermuda. By Tuesday, however, environmental conditions are forecast to become less conducive for tropical cyclone formation. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Sat Aug 14, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Grace, located just north of Guadeloupe. The National Hurricane Center is issuing advisories on the Remnants of Fred which are expected to re-generate into a tropical cyclone over the southeastern Gulf of Mexico tonight or Sunday. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.

  • 1. A small area of low pressure associated with disorganized showers and thunderstorms has developed more than 200 miles north-northeast of Bermuda. Some gradual development is possible over this weekend into early next week as this system drifts slowly southward near Bermuda over the next few days. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent.

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