ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM Hurricane Helene Discussion Number 22 NWS National Hurricane Center Miami FL AL082018 500 PM AST Wed Sep 12 2018 The eye has continued to become less distinct in conventional imagery, but the overall convective pattern remains well organized and symmetric. Based on the latest Dvorak estimates, the initial intensity is lowered to 75 kt. Most of the guidance show a significant increase in the shear in 24 hours, but the SSTs are not changing much for the next 2 days or so, thus gradual weakening is forecast. After that time, both shear and SSTs will become highly unfavorable, resulting in additional weakening. By the end of the forecast period, Helene should have acquired extratropical characteristics. The hurricane is moving toward the north or 350 degrees at 12 kt, embedded in the southerly flow to the east of the digging trough over the central Atlantic. Since the trough is forecast to amplify, Helene will be forced to turn to the north-northeast and northeast with an increase in forward speed. The global models remain in fairly good agreement on the current forecast track of Helene, and they all bring the cyclone near the Azores in about 3 days. Interests in those islands should closely monitor the progress of Helene over the next several days. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 21.4N 36.7W 75 KT 85 MPH 12H 13/0600Z 23.1N 37.1W 70 KT 80 MPH 24H 13/1800Z 26.0N 37.2W 60 KT 70 MPH 36H 14/0600Z 29.0N 36.5W 55 KT 65 MPH 48H 14/1800Z 32.5N 35.5W 55 KT 65 MPH 72H 15/1800Z 39.0N 32.0W 50 KT 60 MPH 96H 16/1800Z 43.0N 24.0W 45 KT 50 MPH 120H 17/1800Z 47.5N 14.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Avila NNNN
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