Issued at 500 PM AST Thu Aug 21 2025
663 WTNT45 KNHC 212032 TCDAT5 Hurricane Erin Discussion Number 42 NWS National Hurricane Center Miami FL AL052025 500 PM AST Thu Aug 21 2025 Erin is gradually pulling away from the U.S., but coastal flooding and tropical storm conditions continue across portions of the North Carolina and Virginia coastline. A pair of ASCAT passes from a few hours ago confirmed Erin's large size with its associated tropical-storm-force winds extending nearly 500 n mi across. In fact, comparing Erin with other systems around the same intensity and in similar locations over the past couple of decades indicates that it is around the 90th percentile in size. Overall, the structure of the system has changed little since the aircraft departed earlier today, and based on that data and the satellite intensity estimates, the initial intensity is held at 85 kt. Erin is producing very rough seas, and the associated swells are covering nearly the entire western Atlantic from the Bahamas to Atlantic Canada. Erin has turned northeastward, and it is currently moving at 050/17 kt. A faster motion to the northeast or east-northeast is expected within the mid-latitude westerlies over the next few days, taking Erin out to sea over the north Atlantic. The models are in good agreement, and only minor changes were made to the previous NHC forecast. The environmental conditions are expected to become increasingly hostile around Erin, as southwesterly vertical wind shear is likely to steadily increase while humidity values and sea surface temperatures decrease. This should result in weakening, but Erin will likely only slowly lose strength due to its large size. Erin is expected to cross the north wall of the Gulf Stream in a couple of days, and that should help lead to its extratropical transition. The NHC intensity forecast is similar to the previous one, and follows HCCA and IVCN in the short term, but leans toward the global model guidance during the predicted extratropical phase. KEY MESSAGES: 1. Erin will continue to produce life-threatening surf and rip currents along the beaches of the Bahamas, much of the east coast of the U.S., Bermuda, and Atlantic Canada during the next several days. Beachgoers in those areas should follow advice from lifeguards, local authorities, and beach warning flags. 2. Storm surge flooding will continue on the North Carolina Outer Banks through tonight. The storm surge will be accompanied by large waves, leading to significant beach erosion and overwash, making some roads impassible. 3. Tropical storm conditions are expected for a few more hours along portions of the northeast North Carolina and Virginia coast. Wind gusts to tropical storm force are likely along portions of the remainder of the U.S. Mid-Atlantic and southern New England coasts today through early Friday. 4. Tropical storm conditions are expected on Bermuda this evening through early Friday. Gusts to gale force are possible along the coast of Nova Scotia on Friday and the Avalon Peninsula of Newfoundland on Saturday. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 36.4N 69.1W 85 KT 100 MPH 12H 22/0600Z 38.0N 66.2W 80 KT 90 MPH 24H 22/1800Z 40.0N 61.3W 75 KT 85 MPH 36H 23/0600Z 41.8N 55.3W 75 KT 85 MPH 48H 23/1800Z 44.7N 47.3W 70 KT 80 MPH...POST-TROP/EXTRATROP 60H 24/0600Z 47.9N 39.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 72H 24/1800Z 50.9N 31.8W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 25/1800Z 55.8N 22.4W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 26/1800Z 56.9N 20.5W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Cangialosi