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#105708 (Received by flhurricane at: 4:31 PM 23.Aug.2006) TCDAT4 TROPICAL STORM DEBBY DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006 500 PM EDT WED AUG 23 2006 THE ORGANIZATION OF DEBBY HAS DETERIORATED SIGNIFICANTLY THIS AFTERNOON...WITH THE CIRCULATION CENTER RUNNING NORTHWESTWARD AHEAD OF DECAYING CONVECTION. WHILE THIS IS PARTLY DIURNAL...DEBBY IS MOVING THROUGH A DRY AND STABLE AIR MASS AND OVER 26C WATERS. DVORAK T NUMBERS ARE DOWN SHARPLY...AND THE INITIAL INTENSITY IS LOWERED TO 40 KT. THE THERMODYNAMIC ENVIRONMENT IS EXPECTED TO SUPPORT...AT BEST...ONLY SLOW DEVELOPMENT FOR THE NEXT DAY OR TWO...BUT DEBBY WILL BE MOVING BACK OVER WARMER WATERS AFTER THAT. ALTHOUGH DEBBY IS EXPECTED TO ENCOUNTER SOUTHERLY SHEAR FROM AN UPPER-LEVEL LOW LATE IN THE FORECAST PERIOD...BOTH THE SHIPS AND GFDL GUIDANCE INDICATE THAT THIS SHOULD NOT PREVENT A RESTRENGTHENING AND THE LONGER RANGE OFFICIAL INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY. DEBBY CONTINUES TO GAIN LATITUDE AND THE INITIAL MOTION IS NOW 305/17. THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE FORECAST THINKING AND ONLY MINOR ADJUSTMENTS TO THE TRACK. 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. 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. GUIDANCE IS UNANIMOUS ON A GRADUAL TURN TO THE NORTH AHEAD OF THE CENTRAL ATLANTIC TROUGH...WITH DIFFERENCES ONLY IN THE RATE OF RECURVATURE. THE OFFICIAL FORECAST IS A LITTLE TO THE LEFT OF THE GUNA CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 23/2100Z 17.9N 33.0W 40 KT 12HR VT 24/0600Z 19.0N 35.4W 40 KT 24HR VT 24/1800Z 20.3N 38.3W 45 KT 36HR VT 25/0600Z 21.5N 41.2W 50 KT 48HR VT 25/1800Z 22.8N 44.0W 55 KT 72HR VT 26/1800Z 25.5N 48.5W 60 KT 96HR VT 27/1800Z 28.5N 51.5W 65 KT 120HR VT 28/1800Z 32.0N 52.0W 65 KT |