ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM HURRICANE FLORENCE DISCUSSION NUMBER 34 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062006 1100 PM EDT MON SEP 11 2006 THE SATELLITE PRESENTATION OF FLORENCE HAS BEEN DETERIORATING WITH ALMOST ALL OF THE CONVECTION TO THE NORTH AND REMOVED FROM THE CENTER. THE CLOUD PATTERN ALSO SUGGESTS THAT THE CYCLONE MIGHT BE BEGINNING THE FIRST STAGES OF EXTRATROPICAL TRANSITION. DVORAK SATELLITE ESTIMATES ARE DROPPING AND THE INITIAL INTENSITY WILL BE LOWERED TO 75 KT. FURTHER WEAKENING IS LIKELY AS THE HURRICANE SLOWLY TAKES ON NON-TROPICAL CHARACTERISTICS AS IT INTERACTS WITH A FRONTAL BOUNDARY A COUPLE HUNDRED MILES NORTH OF THE CENTER. HOWEVER...ALL GLOBAL MODELS SHOW THAT FLORENCE WILL BE A LARGE POWERFUL EXTRATROPICAL CYCLONE... AND SO DOES THE INTENSITY FORECAST. ONE QUESTION MARK IS HOW FAST FLORENCE COMPLETES ITS EXTRATROPICAL TRANSITION. FSU PHASE-SPACE DIAGRAMS DERIVED FROM GLOBAL MODEL FIELDS WOULD INDICATE FULL TRANSITION BY 3 DAYS. WE ARE INDICATING FLORENCE TO BE EXTRATROPICAL BY 48 HOURS... JUST A LITTLE FASTER THAN THESE MODELS BUT SEEMINGLY REASONABLE SINCE THE HURRICANE IS ALREADY LOOKING A LITTLE LESS THAN TROPICAL. FLORENCE IS SPEEDING UP TONIGHT... NOW MOVING 025/16. A MIDDLE-TROPOSPHERIC TROUGH LOCATED OVER CANADA INTO THE NORTHEAST UNITED STATES SHOULD ACCELERATE THE HURRICANE TOWARD THE NORTH-NORTHEASTWARD FOR 24 TO 36 HOURS. THEREAFTER... A TURN TO THE NORTHEAST SHOULD OCCUR AS THE SYSTEM NEARS NEWFOUNDLAND. MODEL GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO AND THE OFFICIAL FORECAST IS AN UPDATE OF THE PREVIOUS PACKAGE. THE EXTRATROPICAL WIND RADII ARE A BLEND OF THE UKMET AND GFS FORECASTS. A TIGHT PRESSURE GRADIENT BETWEEN FLORENCE AND A STRONG HIGH CENTERED OVER SOUTHEASTERN CANADA CONTINUES TO PRODUCE STRONG NORTHEASTERLY WINDS ALONG AND OFFSHORE OF THE EAST COAST OF THE UNITED STATES. THESE WINDS ARE EXPECTED TO CAUSE VERY ROUGH AND DANGEROUS SURF CONDITIONS WITH POTENTIALLY DEADLY RIP CURRENTS ALONG NEARLY THE ENTIRE ATLANTIC EAST COAST OF NORTH AMERICA FOR THE NEXT SEVERAL DAYS. THE RADII OF 12-FT SEAS SHOWN IN THE FORECAST/ ADVISORY DOES NOT FULLY ACCOUNT FOR THE HUGE AREA OF HIGH WAVES INDIRECTLY ASSOCIATED WITH THIS HURRICANE. FORECAST POSITIONS AND MAX WINDS INITIAL 12/0300Z 35.8N 63.9W 75 KT 12HR VT 12/1200Z 37.8N 62.6W 70 KT 24HR VT 13/0000Z 40.6N 59.9W 65 KT 36HR VT 13/1200Z 44.0N 56.4W 60 KT...BECOMING EXTRATROPICAL 48HR VT 14/0000Z 46.5N 51.5W 60 KT...EXTRATROPICAL 72HR VT 15/0000Z 49.5N 37.0W 45 KT...EXTRATROPICAL 96HR VT 16/0000Z 52.0N 20.0W 40 KT...EXTRATROPICAL 120HR VT 17/0000Z...ABSORBED $$ FORECASTER BLAKE/AVILA NNNN
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Page last modified: Tuesday, 12-Sep-2006 02:35:01 UTC