|
Show Selection: |
| #1155943 (Received by flhurricane at: 4:56 PM 04.Oct.2023) TCDAT2 Tropical Storm Philippe Discussion Number 46 NWS National Hurricane Center Miami FL AL172023 500 PM AST Wed Oct 04 2023 Philippe still has an elongated circulation with discrete clusters of deep convection extending well to the east and south of the center. Aircraft and satellite-derived wind data suggest that the maximum winds have decreased a bit, and Philippe is barely a tropical storm. An Air Force Reserve Hurricane Hunter aircraft only measured peak 850-mb flight-level winds of 39 kt, and although SFMR winds were reported between 35-40 kt, a comparison with ASCAT data and a visual assessment from the flight crew indicate that these data were at least 10 kt too high. The consensus of all available data suggest that 35 kt is a more representative value for the initial intensity. The latest fixes indicate that Philippe has turned northward with an initial motion of 350/10 kt. A northward motion with an increase in forward speed is expected through the next 3 days while Philippe moves between a deep-layer trough just east of Florida and the subtropical ridge over the central Atlantic. After day 3, a larger trough is forecast to move across eastern North America and become negatively tilted, which is expected to cause Philippe to bend to the north-northwest when it reaches Atlantic Canada or eastern New England over the weekend. The track models (at least the ones that carry Philippe for the entire forecast period) remain in good agreement on this scenario, and the NHC track forecast is close to the HCCA consensus aid. The forecast for Philippe`s intensity and structure remains complex. The 12Z GFS still shows a separate non-tropical low developing over the western Atlantic, with Philippe becoming absorbed by the warm front to the east of the low in 2-3 days. However, that appears to be an outlier scenario at this time since the ECMWF, UKMET, and Canadian models keep Philippe as a distinct and dominant low. Even if it doesn`t become absorbed, Philippe is likely to become frontal by day 3, and the NHC forecast now shows the system as extratropical by Saturday afternoon. Little change in strength is likely during the next couple of days, but Philippe could strengthen a little due to baroclinic influences while it goes through extratropical transition. The NHC intensity forecast is below the intensity consensus aids for the first 48 hours, but then is between IVCN and the ECMWF after that time. KEY MESSAGES: 1. Tropical storm conditions are expected on Bermuda beginning early Friday morning, and a Tropical Storm Warning is now in effect. Heavy rainfall will begin to affect the island on Thursday. 2. 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 04/2100Z 22.6N 65.9W 35 KT 40 MPH 12H 05/0600Z 24.0N 66.1W 35 KT 40 MPH 24H 05/1800Z 26.6N 66.0W 35 KT 40 MPH 36H 06/0600Z 29.8N 65.7W 40 KT 45 MPH 48H 06/1800Z 33.3N 65.3W 45 KT 50 MPH 60H 07/0600Z 36.9N 65.4W 50 KT 60 MPH 72H 07/1800Z 40.9N 65.9W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 08/1800Z 50.5N 69.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 09/1800Z...DISSIPATED $$ Forecaster Berg |
