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| #521144 (Received by flhurricane at: 10:53 AM 25.Jun.2012) TCDAT4 TROPICAL STORM DEBBY DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012 1000 AM CDT MON JUN 25 2012 THERE HAS BEEN NO SIGNIFICANT DEEP CONVECTION NEAR THE CENTER OF DEBBY FOR OVER 12 HOURS. WHAT CONVECTION REMAINS IS PRIMARILY LOCATED IN A FRAGMENTED BAND WELL EAST OF THE CENTER...AND SOUNDINGS ALONG THE GULF COAST INDICATE THAT THE ENTRAINMENT OF DRY MID-LEVEL AIR IS AFFECTING THE STORM. IN ADDITION...THE SLOW MOVEMENT OF DEBBY HAS INDUCED OCEANIC UPWELLING AND COOLING UNDERNEATH THE CYCLONE AND MAY HAVE CONTRIBUTED TO THE OBSERVED WEAKENING. LATEST DATA FROM THE RECONNAISSANCE AIRCRAFT INDICATE THAT THE MAXIMUM WINDS ARE NEAR 40 KT. WITH DRY AIR LURKING AND WESTERLY SHEAR ON THE INCREASE OVER THE NEXT COUPLE DAYS... SIGNIFICANT RE-INTENSIFICATION OF THE CYCLONE PRIOR TO LANDFALL SEEMS UNLIKELY. THE NEW NHC FORECAST IS ADJUSTED DOWNWARD IN LINE WITH CURRENT TRENDS AND THE LATEST INTENSITY GUIDANCE. AIRCRAFT AND SATELLITE FIXES HAVE SHOWN LITTLE OVERALL MOVEMENT OVER THE PAST 12 TO 18 HOURS... ALTHOUGH RECENT SATELLITE IMAGERY INDICATES AN EAST-NORTHEASTWARD TO NORTHEASTWARD SHORT-TERM MOTION. AT THE MOMENT...IT IS UNCLEAR WHETHER THE CURRENT MOTION REPRESENTS A MEANDERING OR A MORE DECIDED MOTION. ON THE LARGE SCALE...DEBBY IS TRAPPED IN A REGION OF WEAK STEERING IN BETWEEN A STRONG MID-LEVEL RIDGE OVER THE PLAINS AND ONE OVER THE SUBTROPICAL CENTRAL ATLANTIC. GLOBAL MODELS DEPICT AN AMPLIFYING TROUGH OFFSHORE THE EASTERN SEABOARD CAUSING DEBBY TO MOVE GENERALLY EASTWARD THROUGH THE FORECAST PERIOD...WITH THE CENTER EMERGING OVER THE SOUTHWEST ATLANTIC BY DAY 5. THE ECMWF/GFS SOLUTIONS BEGIN TO LIFT OUT THE WESTERN ATLANTIC TROUGH IN ABOUT 72 HOURS...WHICH COULD LEAVE DEBBY IN WEAK STEERING CURRENT AGAIN AFTER THAT TIME. SINCE YESTERDAY... THE GUIDANCE HAS COME INTO BETTER AGREEMENT...WITH ONLY THE UKMET NOW SHOWING A WESTWARD MOTION. IN ADDITION...THE LATEST GFS ENSEMBLE MEMBERS FAVOR AN EASTWARD MOTION BY ABOUT A 3 TO 1 RATIO. THE NEW FORECAST TRACK REPRESENTS A SUBSTANTIAL CHANGE FROM THE PREVIOUS ONE BUT IS STILL SLOWER THAN THE MULTI-MODEL CONSENSUS IN THE SHORT TERM. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 28.6N 85.2W 40 KT 45 MPH 12H 26/0000Z 28.8N 85.1W 35 KT 40 MPH 24H 26/1200Z 28.9N 84.9W 35 KT 40 MPH 36H 27/0000Z 29.0N 84.7W 35 KT 40 MPH 48H 27/1200Z 29.2N 84.4W 35 KT 40 MPH 72H 28/1200Z 29.5N 83.5W 35 KT 40 MPH 96H 29/1200Z 29.5N 82.5W 30 KT 35 MPH...INLAND 120H 30/1200Z 29.5N 81.0W 30 KT 35 MPH $$ FORECASTER KIMBERLAIN/FRANKLIN |
