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| #1108197 (Received by flhurricane at: 10:47 AM 21.Sep.2022) TCDAT3 Tropical Storm Gaston Discussion Number 5 NWS National Hurricane Center Miami FL AL082022 Issued by the NWS Weather Prediction Center College Park MD 300 PM GMT Wed Sep 21 2022 Satellite images indicate that Gaston continues to produce convection that has become increasingly symmetric around the center. In addition, there is a broken band of thunderstorms on the eastern side of the system. The Dvorak classifications from TAFB and SAB were both 3.5/55 kt. A recent ASCAT-B pass indicate that Gaston has a relatively symmetric wind field with maximum winds in the 45-50 kt range. Based on this data, the initial intensity remains 55 kt for this advisory. It is worth mentioning that satellite data indicate that Gaston is not purely tropical and is likely a hybrid system gaining energy from baroclinic sources. Gaston continues to track northeastward over the north-central Atlantic, with the latest initial motion estimated to be 035/14 kt. Although there is no significant change to the forecast reasoning, there is a modest amount of model spread in the details of the future steering pattern. The NHC track is faster and a tad south of the previous forecast, trending toward the latest consensus models. Gaston is expected to turn to the east in a day or so when it moves on the northern side of a subtropical ridge and then will likely slow down considerably or completely stall near or just west of the western Azores late this week. If the storm survives, a turn to the north or northwest could occur over the weekend. The storm could strengthen a little today given recent trends in its convective development near and around the center. However, weakening should begin on Thursday when Gaston moves over cooler waters and into a region of drier air and slightly stronger westerly vertical wind shear. An approaching mid-level trough should aid in the system`s transition to an extratropical cyclone in a couple of days or so. The NHC intensity forecast lies near the middle of the guidance envelope. Interests in the Azores should continue to monitor the forecast for Gaston. For additional information, see warnings and products issued by the meteorological service in the Azores. FORECAST POSITIONS AND MAX WINDS INIT 21/1500Z 38.3N 41.3W 55 KT 65 MPH 12H 22/0000Z 39.5N 39.0W 60 KT 70 MPH 24H 22/1200Z 40.6N 35.6W 55 KT 65 MPH 36H 23/0000Z 40.9N 32.6W 55 KT 65 MPH 48H 23/1200Z 40.8N 30.7W 50 KT 60 MPH 60H 24/0000Z 40.5N 30.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 24/1200Z 40.0N 30.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 25/1200Z 41.2N 34.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 26/1200Z 42.5N 36.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Cangialosi/Kong/Gallina |
