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| #1155232 (Received by flhurricane at: 11:04 AM 30.Sep.2023) TCDAT2 Tropical Storm Philippe Discussion Number 29 NWS National Hurricane Center Miami FL AL172023 1100 AM AST Sat Sep 30 2023 The satellite presentation of Philippe has not changed much this morning. The partially exposed low-level circulation lies on the western edge of a deep convective mass, as northwesterly shear continues to affect the storm`s stucture. Recent UW-CIMSS objective estimates and subjective Dvorak classifications from TAFB and SAB have generally held steady, and so the initial intensity remains at 45 kt for this advisory. The Air Force Reserve Hurricane Hunters are scheduled to investigate the system later today. The estimated initial motion of Philippe is southwestward (210/4 kt). Philippe is not expected to move much during the next 12-24 h, although there is uncertainty even in the near term related to the extent of the interaction between Philippe and Tropical Storm Rina to its northeast. Most of the models show a slow and generally westward motion during the next day or so, which is reflected in the NHC forecast. Then, model spread increases regarding the timing of Philippe`s turn toward the northwest and north early next week. Stronger model solutions (GFS, HAFS-A) depict an earlier turn along the eastern side of the guidance envelope, while weaker models (ECMWF, UKMET) show the storm making it west of 60W before turning. Given the greater-than-normal model spread, the NHC forecast remains near the TVCA and HCCA aids for this portion of the forecast, with a slight westward adjustment from the previous prediction. By days 4-5, Philippe is forecast to move faster toward the north and northeast between a mid-level ridge over the central Atlantic and a deep-layer trough over the western Atlantic. Given the sheared structure of Philippe, only minor intensity fluctuations are expected during the next 12-24 h. Thereafter, the shear is generally forecast to decrease on Monday and Tuesday, although the magnitude remains at least somewhat dependent on how far west Philippe tracks. Based on our latest track forecast, it is assumed that the shear will relax enough to be conducive for some strengthening over the 29-29.5C SSTs, and this prediction shows Philippe becoming a hurricane by 60 h. Overall, the environment appears reasonably favorable for continued strengthening through days 4-5 as the cyclone moves into the subtropical Atlantic. The updated intensity forecast has been raised during this period to show additional strengthening, although it still lies below the IVCN and HCCA aids, so further adjustments could be necessary. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 16.9N 56.3W 45 KT 50 MPH 12H 01/0000Z 16.8N 56.6W 50 KT 60 MPH 24H 01/1200Z 17.0N 57.2W 50 KT 60 MPH 36H 02/0000Z 17.6N 58.0W 55 KT 65 MPH 48H 02/1200Z 18.5N 58.9W 60 KT 70 MPH 60H 03/0000Z 19.7N 59.6W 65 KT 75 MPH 72H 03/1200Z 21.0N 59.9W 70 KT 80 MPH 96H 04/1200Z 24.9N 59.3W 75 KT 85 MPH 120H 05/1200Z 28.5N 57.0W 75 KT 85 MPH $$ Forecaster Reinhart |
