ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE BILL DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009 500 PM AST TUE AUG 18 2009 BILL REMAINS A VERY IMPRESSIVE AND SYMMETRIC HURRICANE IN SATELLITE IMAGERY. THE AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING BILL THIS AFTERNOON REPORTED PEAK 700 MB FLIGHT-LEVEL WINDS OF 114 KT IN THE NORTHEAST QUADRANT. THE SFMR OBSERVED MAXIMUM WINDS AROUND 85 KT IN EACH QUADRANT OF THE HURRICANE. USING A BLEND OF THESE DATA...THE INITIAL INTENSITY HAS BEEN INCREASED TO 95 KT. THIS IS ALSO SUPPORTED BY SUBJECTIVE DVORAK INTENSITY ESTIMATES OF 90 AND 102 KT FROM SAB AND TAFB RESPECTIVELY. THE INITIAL MOTION IS 290/14. THE FORECAST SCENARIO REMAINS UNCHANGED FROM THE PREVIOUS ADVISORY. BILL IS EXPECTED TO GRADUALLY TURN TO THE NORTHWEST DURING THE NEXT DAY OR TWO AS A WEAKNESS DEVELOPS IN THE SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC. THEREAFTER...THE HURRICANE IS FORECAST TO TURN NORTHWARD AHEAD OF A STRONG TROUGH MOVING INTO THE EASTERN UNITED STATES. THE TRACK GUIDANCE ENVELOPE CHANGED VERY LITTLE THROUGH 48 HOURS...BUT HAS GENERALLY SHIFTED WESTWARD DURING THE REMAINDER OF THE FORECAST PERIOD. AS BEFORE THE ECMWF AND GFS ARE ON THE RIGHT SIDE OF THE ENVELOPE WHILE THE UKMET IS ON THE LEFT. THE OFFICIAL FORECAST IS VIRTUALLY UNCHANGED THROUGH DAY 2...AND HAS NOT BEEN ADJUSTED APPRECIABLY BEYOND THAT TIME AS WELL. THE NEW FORECAST LIES BETWEEN THE DYNAMICAL MODEL CONSENSUS AND THE USUALLY WELL-PERFORMING ECMWF AND GFS MODELS. VERTICAL WIND SHEAR IS EXPECTED TO REMAIN LOW AND SSTS GRADUALLY INCREASE ALONG THE FORECAST TRACK DURING THE NEXT COUPLE OF DAYS. THE INTENSITY FORECAST CALLS FOR ADDITIONAL STRENGTHENING DURING THE NEXT COUPLE OF DAYS IN LINE WITH THE CONSENSUS OF THE INTENSITY GUIDANCE. BEYOND 72 HOURS...DECREASING SSTS AND INCREASING SOUTHWESTERLY UPPER-LEVEL WINDS AHEAD OF THE AFOREMENTIONED TROUGH SHOULD INDUCE SLOW WEAKENING. FORECAST POSITIONS AND MAX WINDS INITIAL 18/2100Z 16.6N 52.2W 95 KT 12HR VT 19/0600Z 17.5N 54.3W 105 KT 24HR VT 19/1800Z 18.9N 56.9W 115 KT 36HR VT 20/0600Z 20.7N 59.3W 115 KT 48HR VT 20/1800Z 22.6N 61.8W 115 KT 72HR VT 21/1800Z 27.3N 65.8W 110 KT 96HR VT 22/1800Z 33.5N 68.0W 100 KT 120HR VT 23/1800Z 40.5N 65.5W 85 KT $$ FORECASTER BROWN/CANGIALOSI NNNN
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