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| #1155899 (Received by flhurricane at: 10:51 AM 04.Oct.2023) TCDAT2 Tropical Storm Philippe Discussion Number 45 NWS National Hurricane Center Miami FL AL172023 1100 AM AST Wed Oct 04 2023 Visible satellite images this morning indicate that Philippe`s low-level circulation remains elongated, and the center is still located on the northwestern edge of an area of deep convection. This convective activity continues to produce heavy rains over the U.S. and British Virgin Islands, as well as northeastern Puerto Rico. The initial intensity remains 40 kt based on a blend of the latest subjective and objective satellite estimates, with sustained tropical-storm-force winds limited to the eastern semicircle. Philippe has turned toward the north-northwest with an initial motion of 335/6 kt. The flow between a strong mid-tropospheric high over the central Atlantic and a deep-layer trough just off the east coast of Florida is expected to steer Philippe northward, and at a faster forward speed, beginning tonight and continuing for the next few days. The track guidance is in good agreement on this general scenario, although there is some east-to-west spread among the models related to how Philippe interacts with a non-tropical low that is forecast to develop to its west in about 2-3 days. After day 3, a deeper trough is forecast to swing across eastern North America, and much of the guidance suggests that Philippe might bend back to the left a bit and approach Atlantic Canada or eastern Maine in 3-4 days. Overall, the NHC track forecast is near the middle of the guidance envelope, close to the TVCX and HCCA consensus aids, and is also nearly identical to the previous prediction. Overall, moderate-to-strong vertical shear is expected to persist over Philippe during the next few days, and very little change in intensity is forecast during that time. Once Philippe begins to interact with the developing low pressure to its west and the associated upper-level trough, baroclinic influences could support some strengthening. This strengthening is shown by most of the intensity models, including the GFS and ECMWF global models, and the official forecast therefore shows a peak intensity of 50 kt at 60 and 72 hours. Model-based phase-space diagrams, simulated satellite imagery, and SHIPS diagnostics all suggest that Philippe will become attached to a front between days 3 and 4 to the north of Bermuda, and the official forecast therefore shows a completion of extratropical transition by Sunday morning. KEY MESSAGES: 1. Heavy rainfall from Philippe is expected to produce scattered flash flooding across portions of the U.S. and British Virgin Islands through today. Heavy rainfall from Philippe will begin to affect Bermuda on Thursday. 2. Tropical storm conditions are possible on Bermuda beginning Friday morning, and a Tropical Storm Watch is now in effect for the island. 3. Philippe is likely to move over portions of Atlantic Canada and eastern New England, likely as a post-tropical cyclone, this weekend. Regardless of Philippe`s intensity or structure, interests in those areas should monitor the storm`s progress and be prepared for the possibility of strong winds and heavy rainfall. FORECAST POSITIONS AND MAX WINDS INIT 04/1500Z 21.2N 65.7W 40 KT 45 MPH 12H 05/0000Z 22.3N 66.0W 40 KT 45 MPH 24H 05/1200Z 24.7N 66.2W 40 KT 45 MPH 36H 06/0000Z 27.6N 65.9W 45 KT 50 MPH 48H 06/1200Z 30.8N 65.3W 45 KT 50 MPH 60H 07/0000Z 34.2N 65.1W 50 KT 60 MPH 72H 07/1200Z 37.8N 65.3W 50 KT 60 MPH 96H 08/1200Z 46.8N 67.8W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 09/1200Z 52.9N 71.9W 25 KT 30 MPH...POST-TROP/EXTRATROP $$ Forecaster Berg |
