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| #1157039 (Received by flhurricane at: 10:38 AM 12.Oct.2023) TCDAT4 Tropical Storm Sean Discussion Number 7 NWS National Hurricane Center Miami FL AL192023 1100 AM AST Thu Oct 12 2023 Sean remains a poorly organized tropical cyclone on visible and infrared satellite imagery this morning. The low-level center is exposed on GOES-16 1-minute visible imagery, and displaced to the west of the main convective band. The overall satellite appearance has resulted in subjective Dvorak data-T numbers of T1.5/T2.0 from TAFB and SAB, respectively. However, recent scatterometer passes from both ASCAT-B and ASCAT-C depict a swath of tropical-storm-force winds to the northeast of the center. Given this scatterometer data, the initial intensity is raised back to 35 kt for this advisory, making Sean a tropical storm once again. The tropical storm is moving northwestward at 305/8 kt. A weak low- to mid-level ridge to the north and northeast of Sean should steer the cyclone west-northwestward or northwestward throughout the forecast period. There was a nudge to the right with the latest model track guidance, and the NHC track has been adjusted slightly right accordingly, and lies near the simple and corrected consensus aids. Westerly vertical wind shear is expected to persist over the system for the next day or so. This shear is forecast to then decrease along Sean's forecast track. However, the system will also be moving into a drier airmass and less favorable upper-level environment. Simulated satellite imagery from the GFS and ECMWF models suggest that Sean could struggle to produce organized convection in the coming days. While small intensity fluctuations are possible, as seen this morning, the NHC intensity forecast remains near the HCCA and IVCN consensus aids, keeping Sean a tropical storm the next day or so, then weakening back into a depression once again. Afterwards, the system is forecast to degenerate into a post-tropical remnant low and dissipate into a trough by day 4. Some of the global models suggest that each of these transitions could occur even sooner than what is shown in the official forecast. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 13.1N 37.2W 35 KT 40 MPH 12H 13/0000Z 13.5N 38.4W 35 KT 40 MPH 24H 13/1200Z 14.4N 40.1W 35 KT 40 MPH 36H 14/0000Z 15.6N 41.6W 30 KT 35 MPH 48H 14/1200Z 16.9N 42.9W 30 KT 35 MPH 60H 15/0000Z 18.2N 44.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 15/1200Z 19.0N 45.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 16/1200Z...DISSIPATED $$ Forecaster Kelly |
