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| #1108351 (Received by flhurricane at: 10:56 AM 22.Sep.2022) TCDAT3 Tropical Storm Gaston Discussion Number 9 NWS National Hurricane Center Miami FL AL082022 Issued by the NWS Weather Prediction Center College Park MD 300 PM GMT Thu Sep 22 2022 Gaston has been relatively steady in strength during the past several hours. Recent visible and microwave images indicate that the storm has a fairly well-defined inner core. However, an SSMI overpass shows that the system is tilted in the vertical due to west-southwesterly shear. The 12Z Dvorak estimates from TAFB and SAB were unchanged, and the initial intensity remains 55 kt at the high end of the classifications. An ASCAT-B pass showed peak winds of around 45 kt in the southeastern quadrant and given the low bias of the instrument for these cases, this data also supports the 55-kt initial wind speed. The 34-kt wind radii has been expanded outward based on the scatterometer data. The storm is still moving east-northeastward at 18 kt on the northwestern periphery of a subtropical ridge. A turn to the east and a reduction in forward speed are expected tonight, followed by a clockwise loop near or over the central and western Azores on Friday and Saturday as the storm moves on the south side of another ridge. The models have generally changed little this cycle, and the NHC track forecast is very similar to the previous one. Despite moderate to strong shear, relatively dry air, and cool SSTs, Gaston has been maintaining its strength. Given that these conditions are only expected to gradually worsen for the system, a slow weakening trend seems likely. The models all show a similar theme, and the NHC intensity forecast lies near the middle of the guidance envelope. Gaston is expected to become post-tropical in a couple of days when it merges with an approaching shortwave trough. Key Messages: 1. Tropical storm conditions are expected to begin tonight in the western Azores and will likely spread to the central Azores on Friday. 2. Gaston is expected to produce heavy rainfall over the western and central Azores beginning tonight and continuing into Saturday. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 40.9N 33.8W 55 KT 65 MPH 12H 23/0000Z 41.2N 31.2W 55 KT 65 MPH 24H 23/1200Z 40.7N 29.3W 55 KT 65 MPH 36H 24/0000Z 39.6N 29.0W 50 KT 60 MPH 48H 24/1200Z 38.9N 30.0W 50 KT 60 MPH...POST-TROPICAL 60H 25/0000Z 38.9N 31.7W 45 KT 50 MPH...POST-TROPICAL 72H 25/1200Z 39.1N 33.6W 45 KT 50 MPH...POST-TROPICAL 96H 26/1200Z 38.3N 37.2W 35 KT 40 MPH...POST-TROPICAL 120H 27/1200Z 37.2N 40.7W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Cangialosi/Weiss/Taylor |
