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| #1155188 (Received by flhurricane at: 4:43 AM 30.Sep.2023) TCDAT2 Tropical Storm Philippe Discussion Number 28 NWS National Hurricane Center Miami FL AL172023 500 AM AST Sat Sep 30 2023 An Air Force Reserve Hurricane Hunter crew investigated Philippe a few hours ago and found that the minimum pressure had fallen to 999 mb, however the maximum winds do not appear to have increased. The maximum flight-level wind was 46 kt at 700 mb, and SFMR readings outside of deep convection were as high as 45 kt (SFMR measurements higher than 50 kt appeared questionable due to coincident heavy rain). The low-level center remains located on the northwestern edge of the deep convection due to continued shear. The reconnaissance fixes showed that Philippe has been moving toward the south-southwest (200 degrees) at about 4 kt. The storm has moved a little farther south than expected, possibly due to a more pronounced binary interaction with Tropical Storm Rina about 450 n mi to its east-northeast. As the interaction continues, Philippe is forecast to move slowly toward the west and then northwest during the next few days. However, there is still quite a bit of model spread in how far west Philippe will get before it turns, and the ECMWF and HAFS-B models in particularly bring the storm very close to the northern Leeward Islands in about 48 hours. The NHC track forecast has been shifted west of the previous prediction and lies just to the west of the TVCA consensus aid. It is noteworthy that several models and ensemble members still lie west of the new forecast, and it`s possible that additional adjustments may be required in future forecast cycles. All models show Philippe accelerating toward the north and north-northeast by days 4 and 5, steered by the flow between a mid-level high over the central Atlantic and a deep-layer trough over the western Atlantic. The intensity forecast remains tricky and is complicated by competing positive and negative environmental factors. On one hand, moderate-to-strong northwesterly shear is likely to continue at least for the next 48 hours. However, the magnitude of the shear will depend on Philippe`s exact location, and it could also be offset by a more diffluent upper-level environment. Since the storm has already been overachieving in the sheared environment, the NHC intensity forecast shows gradual strengthening during the next few days, and is near or just below the IVCN and HCCA consensus aids through 60 hours. The atmosphere could become more favorable for strengthening after that time, and the NHC forecast now shows Philippe reaching hurricane intensity while it recurves toward the subtropical Atlantic. It`s worth noting that this new forecast is still on the conservative side, and that many of the intensity models and consensus aids are at least 20 kt higher on days 4 and 5. Only the ECMWF and its SHIPS and LGEM derivatives remain on the weaker end of the scale and don`t bring Philippe to hurricane strength. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 17.1N 55.9W 45 KT 50 MPH 12H 30/1800Z 16.9N 56.2W 50 KT 60 MPH 24H 01/0600Z 16.9N 56.7W 50 KT 60 MPH 36H 01/1800Z 17.3N 57.5W 55 KT 65 MPH 48H 02/0600Z 18.0N 58.3W 60 KT 70 MPH 60H 02/1800Z 19.2N 59.0W 65 KT 75 MPH 72H 03/0600Z 20.7N 59.5W 65 KT 75 MPH 96H 04/0600Z 24.1N 59.3W 65 KT 75 MPH 120H 05/0600Z 28.1N 56.6W 65 KT 75 MPH $$ Forecaster Berg |
