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#289802 (Received by flhurricane at: 10:49 PM 20.Aug.2009) TCDAT3 HURRICANE BILL DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009 1100 PM AST THU AUG 20 2009 THE SATELLITE PRESENTATION OF BILL HAS CHANGED LITTLE THIS EVENING. THE LARGE EYE REMAINS VERY WELL-DEFINED...HOWEVER THE CLOUD TOPS SURROUNDING THE EYE HAVE WARMED SLIGHTLY DURING THE PAST COUPLE OF HOURS. THE NOAA RECONNAISSANCE AIRCRAFT THAT HAS BEEN SAMPLING THE CORE OF THE HURRICANE THIS EVENING REPORTED A PEAK BELIEVABLE FLIGHT-LEVEL WIND OF 127 KT. ALTHOUGH HIGHER WIND SPEEDS WERE REPORTED...THE METEOROLOGISTS ON THE AIRCRAFT DID NOT CONSIDER THOSE HIGHER WINDS TO BE VALID. DVORAK DATA T-NUMBERS HAVE DECREASED SLIGHTLY. BASED ON ALL OF THE DATA...THE INITIAL INTENSITY IS HELD AT 110 KT. ENVIRONMENTAL FACTORS ARE EXPECTED TO REMAIN CONDUCIVE FOR SOME RESTRENGTHENING DURING THE NEXT 24 HOURS OR SO. AFTERWARDS...SOME COOLING OF THE SSTS WILL LIKELY INDUCE A SLOW WEAKENING TREND. VERTICAL WIND SHEAR IS PREDICTED BY THE SHIPS MODEL TO REMAIN LIGHT UNTIL THE HURRICANE NEARS THE CANADIAN MARITIMES IN ABOUT 72 HOURS. HOWEVER...SSTS ALONG THE FORECAST TRACK WILL BEGIN TO COOL MORE RAPIDLY AROUND THAT TIME...AND SHEAR IS FORECAST TO INCREASE SIGNIFICANTLY VERY SOON THEREAFTER. THE OFFICIAL WIND SPEED FORECAST IS GENERALLY BETWEEN THE SHIPS AND LGEM GUIDANCE BILL CONTINUES TO MOVE NORTHWESTWARD OR 310/16 KT. THERE IS NOT MUCH NEW TO SAY ABOUT THE TRACK FORECAST. BILL IS EXPECTED TO TURN NORTHWARD AHEAD OF A STRONG MID-LATITUDE TROUGH THAT WILL MOVE INTO THE EASTERN U.S. DURING THE NEXT COUPLE OF DAYS...AND RECURVE AHEAD OF THAT TROUGH THEREAFTER. THE NEW TRACK FORECAST IS VIRTUALLY UNCHANGED FROM THE PREVIOUS ADVISORY AND IS ONCE AGAIN IN EXCELLENT AGREEMENT WITH THE TIGHTLY CLUSTERED MODEL GUIDANCE. LARGE SWELLS GENERATED BY THIS HURRICANE ARE AFFECTING...OR WILL AFFECT...A LARGE PORTION OF THE WESTERN NORTH ATLANTIC COASTAL AREA DURING THE NEXT FEW DAYS. THESE SWELLS WILL LIKELY CAUSE EXTREMELY DANGEROUS SURF AND LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS ISSUED BY YOUR LOCAL WEATHER OFFICE FOR MORE DETAILS. DATA FROM A TWO-AIRCRAFT SYNOPTIC SURVEILLANCE MISSION CONDUCTED BY NOAA AND U.S. AIR FORCE RESERVE AIRCRAFT THIS EVENING SHOULD BE ASSIMILATED INTO THE INITIALIZATION OF THE 0000 UTC MODEL RUNS. FORECAST POSITIONS AND MAX WINDS INITIAL 21/0300Z 24.9N 64.3W 110 KT 12HR VT 21/1200Z 26.9N 66.1W 115 KT 24HR VT 22/0000Z 29.6N 67.9W 115 KT 36HR VT 22/1200Z 32.7N 68.9W 110 KT 48HR VT 23/0000Z 36.4N 68.6W 100 KT 72HR VT 24/0000Z 44.3N 62.0W 80 KT 96HR VT 25/0000Z 50.5N 43.0W 55 KT...EXTRATROPICAL 120HR VT 26/0000Z 55.0N 20.0W 50 KT...EXTRATROPICAL $$ FORECASTER BROWN/PASCH |