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#872798 (Received by flhurricane at: 4:38 PM 23.Aug.2016) TCDAT2 TROPICAL STORM GASTON DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016 500 PM AST TUE AUG 23 2016 The cloud pattern of Gaston has not changed much during the past several hours, although perhaps the convection has become more symmetric. Satellite classifications are about the same as before, so the initial wind speed remains 55 kt. Gaston has about 24-36 hours to intensify before southwesterly vertical wind shear associated with a mid-tropospheric trough is forecast to increase. This shear should result in some weakening of the cyclone in the 2 or 3 day time frame. Thereafter, Gaston moves away from the trough, and since the cyclone should be over warm waters near 29C, some restrengthing is likely. Considering the complexity of the scenario, the guidance is in relatively good agreement on this pattern. The official forecast follows the trend of the previous forecast and the intensity consensus. The initial motion estimate is 290/16. Gaston should gradually turn northwestward during the next couple of days as it moves around the subtropical ridge. Guidance is in very good agreement on the forecast during that time, and little change is made to the previous NHC track in the shorter term. Beyond 3 days, a break in the subtropical ridge is forecast, although the models are not in great agreement on exactly what longitude Gaston reaches before its likely recurvature. Overall, the model guidance has shifted a bit westward, and the latest NHC track forecast is shifted in that direction. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 14.2N 35.8W 55 KT 65 MPH 12H 24/0600Z 15.2N 38.1W 65 KT 75 MPH 24H 24/1800Z 16.8N 40.7W 75 KT 85 MPH 36H 25/0600Z 18.7N 43.2W 80 KT 90 MPH 48H 25/1800Z 20.8N 45.4W 80 KT 90 MPH 72H 26/1800Z 25.5N 49.6W 70 KT 80 MPH 96H 27/1800Z 28.5N 53.5W 75 KT 85 MPH 120H 28/1800Z 31.0N 54.5W 85 KT 100 MPH $$ Forecaster Blake |