000 WTNT44 KNHC 260300 TCDAT4 TROPICAL STORM DEBBY DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012 1000 PM CDT MON JUN 25 2012 AFTER AN INTENSE BURST OF DEEP CONVECTION NEAR AND NORTH OF THE LOW-LEVEL CENTER THIS LATE AFTERNOON AND EVENING...THE CONVECTIVE CLOUD SHIELD IS SHOWING SIGNS OF SLOWLY PULLING AWAY FROM CENTER OF CIRCULATION DUE TO MODERATE TO STRONG SOUTHWESTERLY VERTICAL WIND SHEAR. THE HIGHEST RELIABLE SFMR WINDS REPORTED BY AN AIR FORCE RESERVE RECON AIRCRAFT THIS EVENING HAS BEEN 42 KT TO THE WEST AND WELL SOUTHEAST OF THE CENTER...ALONG WITH 59-KT AND 56-KT FLIGHT-LEVEL WINDS...RESPECTIVELY. ALTHOUGH THE TALLAHASSEE DOPPLER WEATHER RADAR HAS BEEN INDICATING LARGE WINDS OF 60-65 VELOCITIES BETWEEN 2000 AND 6500 FT IN SOME RATHER VIGOROUS CONVECTION...THOSE CONDITIONS HAVE BEEN OVER LAND. THEREFORE...THE INITIAL INTENSITY WILL REMAIN AT 40 KT. THE MOTION ESTIMATE IS A SLOW DRIFT TO THE NORTHEAST OR 040/02 KT OVER THE PAST 12 HOURS. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS TRACK REASONING. UPPER-AIR DATA AT 18Z AND 00Z INDICATE DEBBY REMAINS TRAPPED IN A BLOCKING RIDGE PATTERN THAT EXTENDS ACROSS THE SOUTHEASTERN U.S. AND INTO THE EASTERN GULF OF MEXICO AND WESTERN ATLANTIC. THE RESULTANT WEAK STEERING FLOW SHOULD KEEP DEBBY MOVING VERY SLOWLY NORTHEAST OR EASTWARD AT LESS THAN 5 KT THROUGHOUT THE FORECAST PERIOD. IN FACT...DEBBY WILL LIKELY REMAIN OVER THE NORTHEASTERN GULF OF MEXICO FOR AT LEAST THE NEXT 2 DAYS BEFORE IT CREEPS SLOWLY ACROSS NORTH FLORIDA IN DAYS 3-4. IN THE ABSENCE OF ANY LARGE-SCALE STEERING FLOW...THE LOW-LEVEL CENTER OF DEBBY WILL CLOSELY FOLLOW ANY DEEP CONVECTION THAT DEVELOPS...WHICH SHOULD REMAIN PRIMARILY TO NORTHEAST OF THE CENTER. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK THROUGH DAY 3...AND IS THEN A LITTLE NORTH OF THE PREVIOUS TRACK AND CLOSE TO THE NHC MODEL CONSENSUS. THE PRESENCE OF DRY MID-LEVEL AIR WRAPPING INTO THE WESTERN AND SOUTHERN PORTION OF THE CIRCULATION...ALONG WITH SOUTHWESTERLY VERTICAL WIND SHEAR OF 20-25 KT FOR THE NEXT 48 HOURS OR SO SHOULD INHIBIT ANY SIGNIFICANT DEVELOPMENT WHILE DEBBY REMAINS OVER WATER. THE SHEAR DECREASES SIGNIFICANTLY BY 72 HOURS AND BEYOND...BUT DEBBY WILL BE OVER OR INTERACTING WITH LAND AT DAYS 3 AND 4...SO THAT WILL PREVENT THE CYCLONE FROM TAKING ADVANTAGE OF THE IMPROVING SHEAR CONDITIONS. BY DAY 5...HOWEVER...DEBBY IS EXPECTED TO BE MOVING OVER THE WARMER WATERS OF THE GULFSTREAM...WHICH MAY ALLOW FOR SOME MODEST STRENGTHENING TO OCCUR AFTER HAVING WEAKENED OVER LAND. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND CLOSELY FOLLOWS THE LGEM INTENSITY MODEL. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 29.2N 85.1W 40 KT 45 MPH 12H 26/1200Z 29.3N 84.9W 40 KT 45 MPH 24H 27/0000Z 29.4N 84.6W 40 KT 45 MPH 36H 27/1200Z 29.5N 84.2W 40 KT 45 MPH 48H 28/0000Z 29.6N 83.6W 40 KT 45 MPH 72H 29/0000Z 29.8N 82.3W 30 KT 35 MPH...INLAND 96H 30/0000Z 30.1N 80.7W 35 KT 40 MPH...OVER WATER 120H 01/0000Z 30.8N 78.7W 40 KT 45 MPH $$ FORECASTER STEWART