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| #1155403 (Received by flhurricane at: 11:04 AM 01.Oct.2023) TCDAT2 Tropical Storm Philippe Discussion Number 33 NWS National Hurricane Center Miami FL AL172023 1100 AM AST Sun Oct 01 2023 Philippe is not a well organized tropical cyclone at this time, with any of the associated deep convection about a degree southeast of the center due to persistent northwesterly shear. Satellite intensity estimates are about the same as before, so the initial wind speed is held 45 kt on this advisory. A scatterometer pass just received also supports that value. The storm appears to be moving westward this morning, judging from fixes on the visible imagery. Weak mid-level ridging is forecast to build east of the tropical cyclone soon, which probably will steer Philippe toward the west-northwest or northwest later today, and eventually northward as it moves into the subtropics. The short-term forecast steering is extremely challenging due to the changing depth of associated deep convection, the cyclone vortex strength, and the related steering flow. Regardless, it is clear that the risk to the northern Leeward Islands has increased, and the new forecast is adjusted west of the previous one, which necessitated the tropical storm watches. Further westward shifts and other watches/warnings are possible later today since Philippe has not been a well-behaved system in such a complex steering flow. Strong shear should continue near Philippe for the next day or so, leading to little overall change in strength during that time. A gradual lessening of the shear is anticipated by Tuesday, but model guidance is in poor agreement on whether the shear will be low enough for significant strengthening, like many of the regional hurricane models suggest, or if Philippe stays sheared like the ECMWF solution. For now, the forecast takes the middle of the road in the guidance, leading to little change from the last NHC prediction. KEY MESSAGES: 1. Tropical storm conditions are possible across portions of the northern Leeward Islands Monday and Monday night while Philippe passes near or just northeast of the area, and a Tropical Storm Watch has been issued for Antigua and Barbuda. Interests elsewhere in the northern Leeward Islands should continue to monitor this system as additional watches or warnings could be required later today or tonight. 2. Heavy rainfall from Philippe could produce isolated to scattered flash flooding, particularly across Barbuda and Antigua, through Tuesday. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 16.1N 58.7W 45 KT 50 MPH 12H 02/0000Z 16.5N 59.5W 45 KT 50 MPH 24H 02/1200Z 17.1N 60.5W 45 KT 50 MPH 36H 03/0000Z 17.9N 61.3W 50 KT 60 MPH 48H 03/1200Z 19.0N 62.1W 50 KT 60 MPH 60H 04/0000Z 20.3N 62.3W 50 KT 60 MPH 72H 04/1200Z 22.0N 62.3W 55 KT 65 MPH 96H 05/1200Z 25.8N 61.8W 65 KT 75 MPH 120H 06/1200Z 29.5N 59.0W 75 KT 85 MPH $$ Forecaster Blake |
