ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM DEBBY DISCUSSION NUMBER 10 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006 1100 PM EDT WED AUG 23 2006 AFTER THE BRIEF WEAKENING PHASE DEBBY WENT THROUGH EARLIER AS MENTIONED IN THE PREVIOUS DISCUSSION...THE CYCLONE HAS STARTED TO MAKE A COMEBACK. DEEP CONVECTION HAS REDEVELOPED IN THE WESTERN SEMICIRCLE...AND MICROWAVE SATELLITE DATA INDICATE GOOD BANDING FEATURES AND THAT THE LOW-LEVEL CENTER IS UNDERNEATH THE NORTHEAST PORTION OF THE CONVECTIVE CLOUD CANOPY. THE INTENSITY IS BEING MAINTAINED AT 40 KT AS IN THE PREVIOUS ADVISORY DESPITE SATELLITE INTENSITY ESTIMATES OF ONLY 30 KT FROM ALL THREE AGENCIES. THE INITIAL MOTION ESTIMATE IS 300/16. CONVENTIONAL AND MICROWAVE SATELLITE POSITION ESTIMATES INDICATE DEBBY IS BASICALLY ON TRACK. A GRADUAL MOTION CLOSE TO 290 DEGREES IS EXPECTED TO OCCUR WITHIN THE NEXT 24 HOURS DUE TO MID- TO UPPER-LEVEL SOUTHEASTERLY FLOW FORCING THE CYCLONE ON A SLIGHTLY MORE WESTWARD TRACK NOW THAT DEEP CONVECTION HAS REDEVELOPED ON THE WEST SIDE OF DEBBY. OTHERWISE DEBBY IS FORECAST FOR THE NEXT 4 DAYS TO TO BE STEERED WEST-NORTHWESTWARD AND THEN NORTHWESTWARD AROUND THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE LOCATED TO THE NORTH. BY THE DAY 4-5 TIME PERIOD...ALL THE MODELS AGREE THAT A WEAKNESS WILL DEVELOP IN THE SUBTROPICAL RIDGE BETWEEN 50W-55W LONGITUDE... ALLOWING DEBBY TO MOVE NORTHWARD INTO THAT WEAKNESS. THE UKMET AND GFDL MODELS INDICATE RECURVATURE TO THE NORTHEAST BY DAY 5... WHEREAS THE REST OF THE MODELS MERELY SLOW DOWN THE CYCLONE AND MOVE IT NORTHWARD INTO THE WEAKNESS. THE GFS IS NOW SUGGESTING THAT THE SHORTWAVE TROUGH EXPECTED TO CAUSE THE BREAK IN THE SUBTROPICAL RIDGE MAY RUN OFF AND LEAVE DEBBY CAUGHT IN THE RIDGE AXIS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK AND THE GUNA...GUNS...AND CONU CONSENSUS MODELS. DEBBY IS CURRENTLY OVER 26C SSTS...THE COOLEST WATER IT WILL ENCOUNTER DURING THE NEXT 5 DAYS. VERTICAL SHEAR IS FORECAST TO DECREASE TO LESS THAN 10 KT DURING THE NEXT 12-24 HOURS...SO SOME GRADUAL STRENGTHENING IS POSSIBLE AS THE CYCLONE MOVES OVER WARMER SSTS. BY 72 HOURS... THE VERTICAL SHEAR IS EXPECTED TO INCREASE TO AT LEAST 20 KT...WHICH WILL INHIBIT INTENSIFICATION DESPITE DEBBY MOVING OVER 28C AND WARMER SSTS. HOWEVER...GIVEN THAT THE VERTICAL SHEAR VECTOR WILL BE ALIGNED NEARLY ALONG THE FORECAST TRACK... DEBBY COULD STILL BECOME A CATEGORY 1 HURRICANE...ESPECIALLY BY DAY 5 WHEN THE CYCLONE WILL BE SITUATED IN THE WEAKNESS IN THE SUBTROPICAL RIDGE AND...THUS...IN A LOWER SHEAR ENVIRONMENT. FORECAST POSITIONS AND MAX WINDS INITIAL 24/0300Z 18.8N 34.7W 40 KT 12HR VT 24/1200Z 19.8N 36.8W 40 KT 24HR VT 25/0000Z 21.1N 39.7W 45 KT 36HR VT 25/1200Z 22.3N 42.5W 50 KT 48HR VT 26/0000Z 23.6N 45.0W 55 KT 72HR VT 27/0000Z 26.4N 49.2W 60 KT 96HR VT 28/0000Z 29.5N 51.5W 65 KT 120HR VT 29/0000Z 33.0N 51.5W 65 KT $$ FORECASTER STEWART NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:35 UTC