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| #1154419 (Received by flhurricane at: 4:41 AM 25.Sep.2023) TCDAT2 Tropical Storm Philippe Discussion Number 8 NWS National Hurricane Center Miami FL AL172023 500 AM AST Mon Sep 25 2023 The satellite appearance of Philippe has remained steady overnight. Burst of deep convection, with cold cloud tops to -80 C, continue from time to time within the overall convective plume. An AMSR microwave pass depicts that the convection remains displaced to the east of the low-level center, with the system still lacking organization. Philippe is struggling to become better organized due to the strong mid-level shear impacting the system. Subjective Dvorak intensity estimates from TAFB and SAB remain at T3.0/45-kt this cycle, and the initial intensity is held at 45 kt. Philippe will continue to be in an environment with moderate to strong mid-level shear, which will limit the overall organization of the system. The storm is traversing fairly warm sea surface temperatures around 29C and favorable mid-level RH values the next few days. Given these mixed parameters and lack of organization, the NHC forecast calls for Philippe to remain fairly steady with the potential for some slow strengthening by the end of the period. However, there remains uncertainty in the intensity forecast given the guidance envelope. The ECMWF suggest the system remains steady or may even weaken, while the GFS depicts strengthening with the system moving far enough north into a lower shear environment. The intensity forecast is similar to the previous, and is closest to the IVCN and HCCA consensus aids. The system is moving west-northwest at an estimated motion of 285/9 kt. Philippe should continue west-northwestward over the next day or two, steered along the southern side of a mid-level ridge. In about 2 days, all models depict a weakness developing in the ridge, but the track guidance diverges quite drastically, and it is directly related to the intensity of the system. A deeper, stronger system, like the GFS depicts, will feel the weakness in the ridge and curve the system faster on a more northwestward track. However, a weaker, shallow cyclone, like the ECMWF depicts, will cause the system to continue on a west-northwestward or even westward track. The NHC track forecast continues to be in the middle of the guidance, and lies close to both the simple and corrected consensus aids. This remains a low confidence track and intensity forecast. FORECAST POSITIONS AND MAX WINDS INIT 25/0900Z 17.4N 43.9W 45 KT 50 MPH 12H 25/1800Z 17.8N 45.7W 45 KT 50 MPH 24H 26/0600Z 18.3N 47.9W 45 KT 50 MPH 36H 26/1800Z 19.0N 49.9W 45 KT 50 MPH 48H 27/0600Z 20.0N 51.8W 45 KT 50 MPH 60H 27/1800Z 21.2N 53.3W 50 KT 60 MPH 72H 28/0600Z 22.4N 54.5W 50 KT 60 MPH 96H 29/0600Z 24.0N 56.0W 55 KT 65 MPH 120H 30/0600Z 25.5N 57.0W 55 KT 65 MPH $$ Forecaster Kelly |
