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Hurricane Henri Forecast Discussion Number 24
2021-08-21 22:33:37| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Sat Aug 21 2021 000 WTNT43 KNHC 212033 TCDAT3 Hurricane Henri Discussion Number 24 NWS National Hurricane Center Miami FL AL082021 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 12H 22/0600Z 38.8N 71.4W 70 KT 80 MPH 24H 22/1800Z 40.8N 72.1W 60 KT 70 MPH 36H 23/0600Z 42.1N 72.4W 40 KT 45 MPH...INLAND 48H 23/1800Z 43.3N 71.9W 25 KT 30 MPH...INLAND 60H 24/0600Z 43.6N 69.9W 25 KT 30 MPH...POST-TROP/INLAND 72H 24/1800Z 44.3N 68.1W 25 KT 30 MPH...POST-TROP/INLAND 96H 25/1800Z...DISSIPATED $$ Forecaster Cangialosi
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