Issued at 1100 PM AST Mon Aug 11 2025
081 WTNT45 KNHC 120233 TCDAT5 Tropical Storm Erin Discussion Number 3 NWS National Hurricane Center Miami FL AL052025 1100 PM AST Mon Aug 11 2025 After struggling earlier during the diurnal convective minimum, a large convective burst has formed and persisted over the center of Erin for the past several hours, and a recent GPM microwave pass from 11/2237 UTC confirmed that the low-level center is underneath this burst. The latest subjective intensity estimates range from 35-45 kt, and the objective intensity estimates from UW-CIMSS have crept up slightly to the 40-45 kt range. The initial intensity is held at 40 kt, which might be a tad conservative. Erin continues moving quickly westward, with the latest motion estimated at 275/18 kt. This general motion with a gradual decrease in forward speed is expected over the next 2 to 3 days as the tropical storm is steered by a mid-level subtropical ridge to its north. Towards the end of the forecast period, the ridge should erode some, which would allow Erin to turn toward the west-northwest and gain some latitude. However, there are some differences in the global models as to how significant the weakness in the ridge will be, and this will affect how far north the cyclone gets by day 5. Some of the recent model solutions are a bit farther to the left (or southwest) at the end of the forecast period. The NHC forecast is nudged only very slightly to the left at days 4-5, and now lies slightly to the north of the latest consensus aids. Based on the model spread, the confidence in the track forecast appears to be about average. Erin is expected to remain in low vertical wind shear conditions for the next 3-4 days. The thermodynamic environment is less favorable in the short-term, with sea-surface temperatures (SSTs) around 26-27C, and stable stratocumulus clouds noted just to the west and northwest of Erin. Only slow strengthening is forecast during the next 1 to 2 days until Erin reaches warmer water. A faster rate of intensification is anticipated after that time. The latest NHC forecast is very similar to the previous one, and lies slightly below the intensity consensus for the first 36 h. Thereafter, the NHC intensity forecast is near the middle of the intensity guidance envelope. It is possible that vertical wind shear could increase in 4 to 5 days, but that will depend on where the upper-level ridge is situated in relation to Erin, which is uncertain at this time. KEY MESSAGES: 1. It is still too early to determine what impacts, if any, Erin may bring to the northern Leeward Islands, Bermuda, or the east coast of the United States. As we approach the climatological peak of the hurricane season, it is an opportune time to ensure your preparedness plans are in place. FORECAST POSITIONS AND MAX WINDS INIT 12/0300Z 17.6N 32.3W 40 KT 45 MPH 12H 12/1200Z 17.4N 35.2W 45 KT 50 MPH 24H 13/0000Z 17.2N 38.8W 50 KT 60 MPH 36H 13/1200Z 17.1N 42.2W 55 KT 65 MPH 48H 14/0000Z 17.4N 45.4W 65 KT 75 MPH 60H 14/1200Z 18.0N 48.4W 75 KT 85 MPH 72H 15/0000Z 18.7N 51.3W 85 KT 100 MPH 96H 16/0000Z 20.3N 56.8W 95 KT 110 MPH 120H 17/0000Z 21.9N 61.5W 100 KT 115 MPH $$ Forecaster Hagen