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| #201873 (Received by flhurricane at: 4:52 PM 19.Jul.2008) TCDAT2 HURRICANE BERTHA DISCUSSION NUMBER 67 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008 500 PM EDT SAT JUL 19 2008 RELATIVELY DEEP CONVECTION PERSISTS ALL THE WAY AROUND THE CIRCULATION CENTER...AND DVORAK ESTIMATES AT 18Z SUPPORT MAINTAINING BERTHA AS A HURRICANE WITH MAXIMUM WINDS OF 65 KT. BERTHA IS CROSSING THE 20 DEGREE CELSIUS ISOTHERM...HOWEVER...AND IT SEEMINGLY CANNOT HOLD ON TO TROPICAL CHARACTERISTICS MUCH LONGER. THE OFFICIAL FORECAST PRESUMES THAT EXTRATROPICAL TRANSITION WILL BE WELL UNDERWAY...ALTHOUGH PERHAPS NOT COMPLETE...BY 12 HOURS AS THE SYSTEM REACHES 17 CELSIUS WATERS...BUT AFTER THAT THE SYSTEM SHOULD BE FULLY EXTRATROPICAL. THIS EVOLUTION IS CONSISTENT WITH THE FSU PHASE SPACE ANALYSIS BASED ON THE GFS GLOBAL MODEL. DESPITE THE TRANSITION...THE WINDS WILL PROBABLY NOT FALL OFF VERY FAST...AND BERTHA WILL BE A LARGE AND POWERFUL EXTRATROPICAL CYCLONE FOR TWO TO THREE DAYS UNTIL IT IS ABSORBED BY OR MERGES WITH ANOTHER SYSTEM CROSSING CANADA. THERE HAS BEEN NO DETECTABLE CHANGE TO THE INITIAL MOTION ESTIMATE OF 035/22. A GRADUAL INCREASE IN FORWARD SPEED IS FORECAST...ALONG ABOUT THE SAME HEADING...IN CLOSE AGREEMENT WITH THE GFS MODEL. THE NEW OFFICIAL TRACK IS VERY SIMILAR TO THE PREVIOUS ADVISORY. FORECAST POSITIONS AND MAX WINDS INITIAL 19/2100Z 44.8N 43.3W 65 KT 12HR VT 20/0600Z 47.9N 40.0W 60 KT 24HR VT 20/1800Z 52.9N 34.3W 55 KT...EXTRATROPICAL 36HR VT 21/0600Z 58.0N 27.2W 50 KT...EXTRATROPICAL 48HR VT 21/1800Z 62.5N 20.0W 50 KT...EXTRATROPICAL 72HR VT 22/1800Z...DISSIPATED $$ FORECASTER KNABB |
