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Tropical Storm Gabrielle Forecast Discussion Number 7
2019-09-05 10:54:52| National Hurricane Center (Atlantic)
Issued at 500 AM AST Thu Sep 05 2019 000 WTNT43 KNHC 050854 TCDAT3 Tropical Storm Gabrielle Discussion Number 7 NWS National Hurricane Center Miami FL AL082019 500 AM AST Thu Sep 05 2019 METEOSAT imagery and an earlier WindSat microwave overpass show Gabielle's poorly defined center of circulation sheared well to the south of the curved convective band features to north, indicative of moderate southerly shear. The initial intensity is held at a generous 45 kt for this advisory, and is based on the subjective T-numbers from TAFB and SAB. Although Gabrielle could experience some intensity fluctuations during the next 24 hours, the cyclone should remain in a rather harsh environment during the next 36-48 hours, due to south to southwesterly vertical shear, some dry air in the middle portions of the atmosphere, and oceanic sea surface temperatures on the order of 25-26C. Afterward, gradual strengthening is forecast as Gabrielle moves into a more favorable upper wind pattern and warmer SSTs, and this is consistent with the IVCN multi-model consensus and the Decay SHIPS. After the adjustment to the south of the previous advisory based on the ASCAT-A/B scatterometer passes and a recent SSMI/S image, the initial motion is estimated to be northwestward, or 315/7 kt. For the next several days, Gabrielle is expected to move generally northwestward toward a large weakness in the mid-Atlantic subtropical ridge. An increase in forward motion is expected as the steering flow strengthens between a cut-off low to the west and high pressure to the northeast. Around days 4 and 5, the cyclone should turn generally northward in response to an approaching mid-tropospheric short wave trough. An adjustment to the right of the previous forecast was made, and the NHC forecast is based on a blend of the various consensus models. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 21.9N 35.0W 45 KT 50 MPH 12H 05/1800Z 22.7N 35.8W 45 KT 50 MPH 24H 06/0600Z 24.2N 37.3W 45 KT 50 MPH 36H 06/1800Z 26.1N 39.1W 45 KT 50 MPH 48H 07/0600Z 28.0N 41.0W 45 KT 50 MPH 72H 08/0600Z 31.6N 46.1W 55 KT 65 MPH 96H 09/0600Z 35.8N 48.7W 60 KT 70 MPH 120H 10/0600Z 40.6N 44.7W 60 KT 70 MPH $$ Forecaster Roberts
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