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| #1150964 (Received by flhurricane at: 4:57 AM 02.Sep.2023) TCDAT5 Post-Tropical Cyclone Idalia Discussion Number 27 NWS National Hurricane Center Miami FL AL102023 500 AM AST Sat Sep 02 2023 Although there has been an increase in convective activity associated with Idalia overnight, the cyclone remains attached to a frontal boundary, and is therefore still analyzed as an extratropical low. The cyclone appears to have deepened slightly with the minimum pressure estimated to be around 999 mb, based on surface observations from Bermuda. With the slight deepening, the initial wind speed has been increased to 50 kt. Winds across Bermuda have increased overnight with the official observing site at the LF Wade International Airport reporting wind gusts as high as 43 kt. Some of the elevated weather stations on the island have reported sustained tropical-storm-force winds. The global models indicate that little change in strength will occur during the next day or so. The guidance also suggests that Idalia may not completely shed its frontal structure despite the presence of deep convection to the northeast of its center today. As a result, the official forecast now shows Idalia potentially becoming a subtropical cyclone for a fairly short period of time this weekend, but confidence in that is low. Regardless of Idalia`s status, tropical-storm-force winds will continue over Bermuda through tonight. Later in the period, the cyclone should gradually weaken while it moves northward over the central Atlantic. The forward speed of Idalia has slowed considerably overnight, with the initial motion estimate of eastward or 090/5 kt. A slow eastward motion is expected today, but a shortwave trough moving off the coast of the northeastern United States tonight should cause Idalia to begin moving northeastward on Sunday. By late Monday the cyclone is expected to turn northward around the eastern side of a developing cut-off low south of Nova Scotia. The track guidance is in somewhat better agreement than it was a day ago, and the latest NHC track prediction is near the center of the model envelope. KEY MESSAGES: 1. Tropical storm conditions will continue in Bermuda into tonight. Heavy rainfall may cause areas of flash and urban flooding on the island. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 31.7N 64.6W 50 KT 60 MPH...POST-TROPICAL 12H 02/1800Z 31.5N 63.9W 50 KT 60 MPH...SUBTROPICAL CYCLONE 24H 03/0600Z 32.1N 62.2W 50 KT 60 MPH 36H 03/1800Z 33.6N 60.2W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 04/0600Z 35.7N 58.6W 50 KT 60 MPH...POST-TROP/EXTRATROP 60H 04/1800Z 37.7N 57.6W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 05/0600Z 40.0N 57.8W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 06/0600Z 41.6N 58.6W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 07/0600Z 43.5N 59.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown |
