Issued at 500 PM AST Mon Aug 11 2025
ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM Tropical Storm Erin Discussion Number 2 NWS National Hurricane Center Miami FL AL052025 500 PM AST Mon Aug 11 2025 Erin's structure this afternoon looks like a tropical cyclone that is struggling with the nearby thermodynamic environment, with only a small patch of deep convection pulsing near the estimated center. It is possible some dry air may have been entrained into the small circulation earlier today, causing its degraded appearance. For now, subjective and objective intensity estimates haven't changed much from the prior advisory, hovering in the 35-42 kt range, so the initial intensity is held at 40 kt this advisory. Erin is still moving quickly off to the west, with the latest estimated motion at 270/18 kt. This general motion with a gradual slowdown in forward speed is expected over the next 48-72 h as the system remains steered by a prominent mid-level ridge to its north. This ridge is forecast to move along with the storm. Towards the end of the forecast period, the ridge should erode some and shift northeastward of Erin, which should allow the cyclone to begin gaining latitude by 120 h. The deterministic track guidance generally agrees on this track evolution, and was only a little faster than the prior cycle. The NHC track forecast is quite similar to the previous one, and lies closest to a blend of the latest 12z GFS and ECMWF forecasts (GFEX). However, it should be noted that spread in the ensemble solutions starts to increase substantially by the end of the forecast period, likely related to the magnitude of ridging that remains poleward of Erin in five days. As mentioned in the prior advisory, while vertical wind shear over Erin is forecast to remain low for the next 3-4 days, the thermodynamic environment is less favorable in the short-term, with sea-surface temperatures between 26-27C, and plenty of stable stratocumulus clouds along the forecast path of the storm. Nonetheless, most of the hurricane-regional models show Erin slowly intensifying during this period. As the storm moves into warmer sea-surface temperatures after 48 h, a faster rate of intensification is anticipated, as long as the shear remains low and if Eric is able to mix out some of the dry air in its vicinity. The intensity guidance is actually a little higher than the previous cycle beyond 60 h, but the latest NHC intensity forecast is similar to the prior one, showing Erin becoming a hurricane in 60 h and a major hurricane in 120 h. This forecast is now a little lower than HAFS-A/B, HMON, and HWRF at the end of the forecast. There are some indications there might some northwesterly shear impinging on the cyclone in 96-120 h, so I elected to stay under these aids for this cycle. 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 11/2100Z 17.4N 30.3W 40 KT 45 MPH 12H 12/0600Z 17.4N 33.4W 45 KT 50 MPH 24H 12/1800Z 17.3N 37.1W 50 KT 60 MPH 36H 13/0600Z 17.1N 40.5W 55 KT 65 MPH 48H 13/1800Z 17.3N 44.0W 60 KT 70 MPH 60H 14/0600Z 17.8N 47.0W 70 KT 80 MPH 72H 14/1800Z 18.5N 50.0W 80 KT 90 MPH 96H 15/1800Z 20.0N 55.6W 95 KT 110 MPH 120H 16/1800Z 22.0N 60.5W 100 KT 115 MPH $$ Forecaster Papin NNNN