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#105671 (Received by flhurricane at: 12:28 PM 23.Aug.2006) TCDAT4 TROPICAL STORM DEBBY DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006 1100 AM EDT WED AUG 23 2006 DEBBY APPEARS TO BE SLOWLY STRENGTHENING...BASED ON THIS MORNING'S QUIKSCAT PASS THAT HAD A COUPLE OF BELIEVABLE 45 KT VECTOR. THE SYSTEM ALSO SHOWED VERY GOOD ORGANIZATION ON AN 11Z MICROWAVE PASS. CONVENTIONAL SATELLITE IMAGERY DOES NOT YET REFLECT THAT LEVEL OF ORGANIZATION...AND DVORAK INTENSITY ESTIMATES RANGE FROM 35 TO 45 KT. THE SYSTEM IS MAINTAINING FAIRLY GOOD OUTFLOW UNDER LIGHT EASTERLY SHEAR. THE THERMODYNAMIC ENVIRONMENT IS EXPECTED TO SUPPORT ONLY SLOW DEVELOPMENT FOR THE NEXT COUPLE OF DAYS...BUT DEBBY WILL BE MOVING BACK OVER WARMER WATERS AFTER THAT. GLOBAL MODELS CONTINUE TO SUGGEST THAT AN UPPER LOW WILL CAUSE AN INCREASE IN SOUTHERLY SHEAR LATE IN THE PERIOD THAT COULD SLOW THE INTENSIFICATION. NEVERTHELESS...THE EXPLICIT INTENSITY GUIDANCE CONTINUES TO INDICATE GRADUAL DEVELOPMENT TO NEAR HURRICANE STRENGTH AND SO DOES THE OFFICIAL FORECAST. THE INITIAL MOTION IS 300/15. DEBBY CONTINUES TO BE STEERED BETWEEN WEST-NORTHWESTWARD AND NORTHWESTWARD AROUND THE SOUTHWESTERN PERIPHERY OF A MID-TO UPPER-LEVEL HIGH CENTERED NEAR THE AZORES. THERE HAS BEEN NO CHANGE TO THE BASIC SYNOPTIC THINKING. A SIGNIFICANT WEAKNESS IN THE SUBTROPICAL RIDGE IS EXPECTED TO DEVELOP AS A MID- TO UPPER-LEVEL TROUGH AMPLIFIES OVER THE CENTRAL ATLANTIC LATE IN THE FORECAST PERIOD. ALL GUIDANCE MODELS EXCEPT THE NOGAPS BEGIN A RECURVATURE BY DAY 5...AND THE NOGAPS DOES SO SHORTLY THEREAFTER. THERE HAS BEEN VERY LITTLE CHANGE TO THE OFFICIAL FORECAST TRACK AT THIS TIME...BUT I NOTE THAT MOST OF THE GUIDANCE SHOWS A HARDER RIGHT TURN BY DAY 5 THAN THE OFFICIAL FORECAST DOES. FORECAST POSITIONS AND MAX WINDS INITIAL 23/1500Z 16.8N 31.5W 45 KT 12HR VT 24/0000Z 17.8N 33.6W 50 KT 24HR VT 24/1200Z 19.1N 36.5W 55 KT 36HR VT 25/0000Z 20.3N 39.3W 55 KT 48HR VT 25/1200Z 21.6N 42.2W 55 KT 72HR VT 26/1200Z 24.5N 47.5W 60 KT 96HR VT 27/1200Z 27.5N 51.0W 65 KT 120HR VT 28/1200Z 30.5N 53.0W 65 KT |