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| #1154531 (Received by flhurricane at: 10:50 PM 25.Sep.2023) TCDAT2 Tropical Storm Philippe Discussion Number 11 NWS National Hurricane Center Miami FL AL172023 1100 PM AST Mon Sep 25 2023 There have not been many changes to the appearance of Philippe tonight. The low-level circulation continues to be primarily exposed to the west of a rather misshapen area of deep convection. While there are a few convective cells that have attempted to redevelop closer to the circulation center, the storm remains disrupted by 20-30 kt of westerly vertical wind shear. While subjective and objective satellite intensity estimates continue to gradually decrease, earlier GOES-16 1-minute meso sector low-level derived motion winds north of Philippe were in the 50-60 kt range, which typically would support somewhat higher winds. In addition, a recently arriving ASCAT-C pass caught the eastern side of the circulation, revealing peak winds in the 40-45 kt range. Therefore, the initial intensity is adjusted to 45 kt for this advisory. Despite the slightly higher initial intensity, Philippe`s future prospects appear increasingly dim (as a tropical cyclone), as the current shear affecting the system is not expected to abate. In fact, this shear may increase further after 48 hours. Because the storm will still continue to traverse warm 29-30C sea-surface temperatures, the storm is likely to continue generating convective bursts east of the center for the majority of the forecast period. However, it appears increasingly likely the shear will not be able to be overcome, and the updated NHC intensity forecast now shows the storm on a slow decline, ending with it becoming a remnant low sometime in the day 4-5 time frame. This forecast is in good agreement with the consensus aids, with remnant low status occuring roughly when the ECMWF shows the system stopping to produce organized convection. Philippe appears to have resumed a more west-northwestward motion at 285/10 kt. Compared to 24 hours ago, the guidance has started to come into better agreement that the storm should maintain a general west-northwestward motion for the next 48-72 hours, not really feeling the mid-level weakness developing to its north as it gradually becomes more vertically shallow. The biggest change compared to the prior advisory is showing a turn more westward by the end of the forecast as the system becomes primarily steered by the more east-to-west oriented low-level ridging. This leftward adjustment to the track forecast is mainly in response to similar leftward shifts in both the GFS and ECMWF ensemble guidance that have shifted to weaker solutions steered by the low-level flow. The NHC track lies roughly in between the reliable consensus aids (TVCN, HCCA) and the ECMWF and its ensemble mean, which remain on the south and west side of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 17.6N 47.8W 45 KT 50 MPH 12H 26/1200Z 18.0N 49.4W 45 KT 50 MPH 24H 27/0000Z 18.8N 51.4W 40 KT 45 MPH 36H 27/1200Z 19.8N 53.1W 40 KT 45 MPH 48H 28/0000Z 20.8N 54.6W 35 KT 40 MPH 60H 28/1200Z 21.5N 56.0W 35 KT 40 MPH 72H 29/0000Z 22.0N 57.4W 35 KT 40 MPH 96H 30/0000Z 22.0N 59.4W 30 KT 35 MPH 120H 01/0000Z 22.0N 61.4W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Papin |
