Issued at 500 AM EDT Tue Sep 30 2025
851 WTNT44 KNHC 300859 TCDAT4 Tropical Storm Imelda Discussion Number 15 NWS National Hurricane Center Miami FL AL092025 500 AM EDT Tue Sep 30 2025 Deep convection has redeveloped on the western side of Imelda during the past several hours, though a fair portion of the circulation has been overtaken by dry air aloft. The last reports overnight from an Air Force Reserve Hurricane Hunter aircraft indicate that the pressure had fallen again to 983 mb, with some increase in flight-level winds as they exited in the western quadrant. Given the improved organization on satellite since the plane left, I'm going to nudge the maximum winds up to 60 kt on this advisory, and another Hurricane Hunter should be in the area this morning. Imelda has taken the long-awaited turn away from the mainland, now estimated at 035/7 kt. This general motion is expected today, followed by a faster motion towards the east-northeast primarily due to increasing mid-latitude southwesterly flow. There remains some speed differences in the models, but it is notable that all of the guidance is near Bermuda between 36-48 h. The new forecast is a touch south of the previous one, perhaps reflecting some binary steering influences from Humberto as the pair of tropical cyclones get closer together. The environment around Imelda is a complicated one, with lots of shear and dry air in the vicinity while the system remains over warm waters. A recent AMSR pass also shows better low-level structure, so intensification is forecast today. Imelda should experience a favorable trough interaction by Wednesday, forcing an increase in the maximum winds as Imelda undergoes a protracted extratropical transition with lots of upper divergence and convection. Every model forecasts a strong sting jet to form on the south and west side of the cyclone on Wednesday during the later stages of the transition. The new forecast is near a mean of the global and regional hurricane models, showing a potent system near Bermuda. Imelda probably won't have a conventional hurricane structure near that island, but there is a significant risk of high winds due to the hybrid tropical cyclone structure expected then. Steady weakening is anticipated by late week after the system passes Bermuda. KEY MESSAGES: 1. Imelda is expected to intensify into a hurricane later today with the cyclone approaching Bermuda during the day Wednesday as a hurricane. A Hurricane Watch is in effect for the island of Bermuda due to the expected onset of tropical storm conditions beginning Wednesday afternoon. 2. Locally heavy rainfall across coastal sections of southeast North Carolina could cause isolated flash and urban flooding through tonight. As Imelda passes near Bermuda, 2 to 4 inches – 50 to 100 mm – of rainfall is expected from Wednesday into Thursday. 3. Swells and high surf from both Humberto and Imelda are expected to produce dangerous marine conditions and rip currents along much of the East Coast of the United States during the next several days. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 28.8N 76.8W 60 KT 70 MPH 12H 30/1800Z 29.3N 75.7W 65 KT 75 MPH 24H 01/0600Z 30.3N 72.7W 70 KT 80 MPH 36H 01/1800Z 31.6N 68.4W 80 KT 90 MPH 48H 02/0600Z 32.8N 63.0W 85 KT 100 MPH 60H 02/1800Z 34.4N 56.9W 75 KT 85 MPH...POST-TROP/EXTRATROP 72H 03/0600Z 36.6N 51.8W 65 KT 75 MPH...POST-TROP/EXTRATROP 96H 04/0600Z 41.5N 48.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 05/0600Z 48.0N 40.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Blake
