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| #1155857 (Received by flhurricane at: 4:56 AM 04.Oct.2023) TCDAT2 Tropical Storm Philippe Discussion Number 44 NWS National Hurricane Center Miami FL AL172023 500 AM AST Wed Oct 04 2023 Philippe remains a disorganized tropical storm this morning, yet continues to produce heavy rainfall over the British and U.S. Virgin Islands. This activity remains displaced well to the southeast of the estimated circulation center, and appears to be more associated with the storm`s inflow interacting with a well-defined mid-level circulation just north of St. Thomas, which is evident from radar in Puerto Rico. Scatterometer data received just after the last advisory showed values around 40 kt in this area of convection, and the initial intensity will be held at 40 kt. This value is on the higher end of the Dvorak intensity estimates, but does match the most recent UW-CIMSS SATCON intensity estimate. The earlier scatterometer data suggested that Philippe had slowed down some, possibly due to the ongoing convection to its southeast, but its latest motion appears to have resumed a more northwestward motion at 325/8 kt. The track guidance remains in agreement about the storm turning more northward later today, with gradual acceleration as the mid-level ridge that has been impeding its poleward progress gradually shifts eastward, and Philippe becomes steered between a deep-layer low to its west, and the aforementioned ridge to its east. Compared to the previous cycle, the guidance has shifted a bit eastward over the first 2-3 days of the forecast period, and the latest NHC track forecast was shifted a bit further east early on, but not as far as the consensus aids. After Philippe passes by Bermuda on Friday, it is forecast to interact with a much more amplified trough swinging into the northeastern United States this weekend. This evolution may result in Philippe`s track potentially bending back north-northwest on Saturday, approaching Atlantic Canada and New England as it phases with the larger trough. There still remains quite a bit of spread in the track guidance by 96 h due to this interaction. The intensity forecast remains murky. Right now, the low-level circulation of Philippe remains diffuse, and even though vertical wind shear could potentially slacken some over the next 24 hours, the cyclone appears to be in no state to intensify in the short-term. Thereafter, Philippe may have an opportunity to take advantage of some synoptic mid-latitude dynamics associated with the initial upper-level trough positioned to the west of its circulation. Thus, some gradual intensification is shown between 36-60 h. With that said, some of the model guidance (like the most recent GFS run) shows Philippe instead being absorbed into this non-tropical feature, though that solution is not shown at this time. Regardless, increasing baroclinicity should also begin to initiate extratropical transition after 48 hours, which is forecast to be fully complete sometime in the 72-96 h forecast time frame. The latest NHC intensity forecast remains near the middle of the guidance envelope, and is also close to the HFIP Corrected Consensus Approach (HCCA). KEY MESSAGES: 1. Heavy rainfall from Philippe is expected to produce scattered flash flooding across portions of the United States & British Virgin Islands through today. 2. Gusty winds are likely to continue across portions of the northern Leeward Islands and the Virgin Islands through early today. 3. The risk is increasing for tropical storm conditions to occur on Bermuda late this week. Interests on Bermuda should monitor the progress of Philippe, and Tropical Storm Watches could become required for the island later today. FORECAST POSITIONS AND MAX WINDS INIT 04/0900Z 20.5N 65.5W 40 KT 45 MPH 12H 04/1800Z 21.4N 65.8W 40 KT 45 MPH 24H 05/0600Z 23.3N 66.0W 40 KT 45 MPH 36H 05/1800Z 26.0N 66.0W 45 KT 50 MPH 48H 06/0600Z 29.0N 65.5W 45 KT 50 MPH 60H 06/1800Z 32.0N 65.0W 50 KT 60 MPH 72H 07/0600Z 35.3N 65.1W 50 KT 60 MPH 96H 08/0600Z 43.1N 66.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 09/0600Z 51.5N 72.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Papin |
