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#109073 (Received by flhurricane at: 10:43 AM 06.Sep.2006) TCDAT1 TROPICAL STORM FLORENCE DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062006 1100 AM EDT WED SEP 06 2006 VISIBLE IMAGERY THIS MORNING SHOWS A WELL-DEFINED LOW-CLOUD SWIRL WITH SOME THIN CONVECTIVE BANDING DEVELOPING IN THE SOUTHEAST AND NORTHWEST QUADRANTS. THE STRONGEST CONVECTION CONTINUES TO BE LOCATED WELL TO THE NORTHEAST OF THE CENTER. SHIP MSJZ8 REPORTED 34 KT WINDS ABOUT 250 MILES FROM THE CENTER...BEYOND THE STRONGEST BAND OF CONVECTION. DVORAK INTENSITY ESTIMATES WERE 45 KT FROM TAFB AND AFWA...AND 35 KT FROM SAB. BASED ON THESE DATA...THE ADVISORY INTENSITY IS INCREASED TO 45 KT. THE CIRCULATION NOW APPEARS TO BE MORE CIRCULAR THAN IT WAS LAST NIGHT...AND I AM PLACING THE OVERALL SYSTEM CENTER ONLY A LITTLE BIT NORTHWEST OF THE CLOUD SWIRL. THE INITIAL MOTION IS 290/10. THE KEY SYNOPTIC FEATURE IN THE SHORT TERM IS THE UPPER LOW CENTERED ABOUT 500 MILES NORTHWEST OF FLORENCE. THIS COULD IMPART MORE OF A NORTHWARD TRACK OVER THE NEXT DAY OR TWO...AS INDICATED BY THE GFDL MODEL...BUT THE REMAINING GUIDANCE IS TIGHTLY CLUSTERED ON A CONTINUED WEST-NORTHWESTWARD MOTION OVER THE NEXT THREE DAYS AS FLORENCE MOVES TO THE SOUTH OF THE MID-LEVEL SUBTROPICAL RIDGE. NEAR THE END OF THE FORECAST PERIOD...FLORENCE IS EXPECTED TO ROUND THE PERIPHERY OF THE RIDGE IN ADVANCE OF A DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES. AT THE MOMENT...MODEL GUIDANCE IS IN EXCELLENT AGREEMENT ON A NORTHWARD TURN. THE INTENSIFICATION OF FLORENCE IS VERY DEPENDENT ON JUST HOW IT INTERACTS WITH THE UPPER-LOW TO ITS NORTHWEST. RIGHT NOW THE LOW IS RESPONSIBLE FOR SOUTHWESTERLY SHEAR AND BROAD-SCALE DESCENT OVER THE CENTER...WITH THE MORE FAVORABLE DIFLUENT FLOW LOCATED WELL TO THE NORTHEAST. THE UPPER-LOW IS FORECAST TO RETROGRADE AND WEAKEN OVER THE NEXT COUPLE OF DAYS...AND THIS WOULD RESULT IN A MORE FAVORABLE PATTERN FOR STRENGTHENING. THE OFFICIAL FORECAST FOLLOWS THIS SCENARIO WITH SLOW DEVELOPMENT OVER THE NEXT 24 HOURS AND MORE SIGNIFICANT DEVELOPMENT AFTER THAT. THE GFDL MODEL IS SLIGHTLY HIGHER THAN THE OFFICIAL FORECAST AND SHOWS FLORENCE AS A MAJOR HURRICANE IN 3 TO 4 DAYS. FORECAST POSITIONS AND MAX WINDS INITIAL 06/1500Z 18.3N 50.9W 45 KT 12HR VT 07/0000Z 19.3N 52.5W 50 KT 24HR VT 07/1200Z 20.5N 54.5W 55 KT 36HR VT 08/0000Z 22.0N 57.0W 65 KT 48HR VT 08/1200Z 23.0N 59.5W 75 KT 72HR VT 09/1200Z 25.0N 64.0W 85 KT 96HR VT 10/1200Z 28.0N 67.0W 95 KT 120HR VT 11/1200Z 31.0N 67.0W 95 KT $$ FORECASTER FRANKLIN |