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Tropical Storm GASTON Forecast Discussion Number 15
2016-08-26 10:51:42| National Hurricane Center (Atlantic)
Issued at 500 AM AST FRI AUG 26 2016 000 WTNT42 KNHC 260851 TCDAT2 TROPICAL STORM GASTON DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016 500 AM AST FRI AUG 26 2016 Gaston is right in the thick of 20-25 kt of southwesterly shear, and the low-level center appears to be near or just inside the southern edge of a ragged central dense overcast. Because Dvorak Current Intensity estimates from TAFB and SAB remain 3.5, the initial intensity is held at 55 kt. With Gaston now moving around the northeastern side of a mid- to upper-level low, the vertical shear is expected to quickly decrease to below 10 kt within the next 12-24 hours. In addition, sea surface temperatures are forecast to increase by another degree or two. Therefore, Gaston is likely to begin strengthening later today, and it should reintensify to a hurricane by tonight or on Saturday. Strengthening is anticipated to continue through days 3 and 4, with Gaston nearing or possibly reaching major hurricane intensity, followed by some weakening on day 5 due to an increase in westerly shear. The reliable intensity models are all within 10-15 kt of each other for the entire forecast period, and the NHC forecast is therefore very close to the ICON intensity consensus. Gaston continues to move northwestward, or 320 degrees at 15 kt. The cyclone is expected to maintain a generally northwestward track but slow down considerably during the next few days after it moves north of the aforementioned mid- to upper-level low and enters a break in the subtropical ridge. After 72 hours, Gaston is expected to reach the mid-latitude westerlies, and a sharp recurvature with acceleration is forecast at the end of the forecast period. While all the track models agree on this scenario, there continue to be differences in the sharpness of Gaston's turn and its forward speed, especially after the turn. Still, the updated NHC track forecast is not too different from the previous one, and it is closest to a clustering of models that includes the GFS, the Florida State Superensemble, and the TVCN multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 23.9N 47.6W 55 KT 65 MPH 12H 26/1800Z 25.5N 49.5W 60 KT 70 MPH 24H 27/0600Z 27.0N 52.1W 65 KT 75 MPH 36H 27/1800Z 28.2N 54.2W 70 KT 80 MPH 48H 28/0600Z 29.2N 55.7W 85 KT 100 MPH 72H 29/0600Z 30.8N 57.1W 95 KT 110 MPH 96H 30/0600Z 32.2N 55.8W 95 KT 110 MPH 120H 31/0600Z 34.0N 51.5W 90 KT 105 MPH $$ Forecaster Berg
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