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| #379577 (Received by flhurricane at: 5:01 AM 29.Sep.2010) TCDAT1 TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL162010 500 AM EDT WED SEP 29 2010 ALTHOUGH THE SATELLITE APPEARANCE OF TROPICAL DEPRESSION SIXTEEN HAS CHANGED LITTLE SINCE THE LAST ADVISORY...DOPPLER RADAR DATA FROM KEY WEST AND MIAMI...ALONG WITH RADAR RADAR FROM CUBA INDICATE CONVECTION HAS INCREASED IN THE NORTHERN SEMICIRCLE. ALSO...AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT FLYING BETWEEN FLORIDA AND CUBA HAS INDICATED SURFACE WINDS OF 33 KT IN UNCONTAMINATED SFMR DATA ABOUT 80-120 NMI EAST-NORTHEAST OF THE CENTER...WHICH IS MUCH CLOSER TO THE CENTER THAN SEEN NOTED IN PRIOR SURFACE OBSERVATIONS AND RECON DATA. THE LARGEST DOPPLER RADAR VELOCITY VALUES DETECTED THUS FAR HAVE BEEN 40-44 KT BETWEEN 6000-12000 FT. THIS INDICATES THAT THE DEPRESSION IS VERY NEAR BECOMING A TROPICAL STORM. THE DEPRESSION IS ON TRACK AND THE THE INITIAL MOTION ESTIMATE IS 020/12. 00Z UPPER-AIR DATA AND WATER VAPOR IMAGERY INDICATED THE MID- TO UPPER-LEVEL FLOW ACROSS THE EASTERN GULF OF MEXICO...THE SOUTHEASTERN U.S. AND THE EXTREME NORTHWESTERN CARIBBEAN SEA HAS BEEN STEADILY BACKING AROUND FROM THE WEST TO THE SOUTH-SOUTHWEST DURING THE PAST 24 HOURS. AS A SERIES OF STRONG SHORTWAVE TROUGHS DIG SOUTHWARD DOWN THE WEST SIDE OF THE LONGWAVE TROUGH LOCATED ALONG 85W...THE FLOW ACROSS FLORIDA SHOULD BECOME MORE SOUTHERLY. THIS FLOW PATTERN SHOULD ACCELERATE THE DEPRESSION TO THE NORTH-NORTHEAST ACROSS SOUTHEASTERN FLORIDA AS A TROPICAL CYCLONE TODAY...AND INTO THE CAROLINAS AS AN EXTRATROPICAL LOW PRESSURE SYSTEM IN 36 HOURS OR SO. ALTHOUGH THE MODEL CONSENSUS HAS SHIFTED A LITTLE TO THE EAST IN THE LATEST MODEL RUNS...THE STRONG BACKING FLOW PATTERN MENTIONED PREVIOUSLY ARGUES FOR KEEPING THE FORECAST TRACK ALONG THE WESTERN OR LEFT SIDE OF THE MODEL GUIDANCE ENVELOPE. AS A RESULT...THE OFFICIAL FORECAST TRACK IS JUST AN EXTENSION OF THE PREVIOUS ADVISORY TRACK. THE VERTICAL SHEAR IS EXPECTED TO DECREASE SLIGHTLY DURING THE NEXT 12 HOURS BEFORE INCREASING TO ABOVE 30 KT IN ABOUT 36 HOURS. AS A RESULT...THERE WILL BE A BRIEF WINDOW OF OPPORTUNITY FOR SOME STRENGTHENING TO OCCUR PRIOR TO THE CYCLONE MAKING LANDFALL ALONG THE SOUTHEASTERN FLORIDA COAST LATER TODAY. EXTRATROPICAL TRANSITION IS EXPECTED TO BEGIN IN 24 HOURS OR SO AND BE COMPLETE BY 36-48 HR AS THE SYSTEM NEARS THE COAST OF THE CAROLINAS WHERE IT IS EXPECTED TO MERGE WITH A FRONTAL SYSTEM. BY 48 HOURS...THE LOW IS FORECAST TO BE ABSORBED BY A LARGER U. S. BAROCLINIC OVER THE NORTHEASTERN UNITED STATES. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IS A BLEND OF THE SHIPS AND LGEM INTENSITY MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 29/0900Z 23.3N 81.4W 30 KT 12HR VT 29/1800Z 25.2N 80.7W 35 KT 24HR VT 30/0600Z 28.9N 79.7W 40 KT 36HR VT 30/1800Z 33.8N 78.6W 40 KT...POST-TROP/EXTRATROP 48HR VT 01/0600Z 40.0N 77.3W 35 KT...POST-TROP/EXTRATROP 72HR VT 02/0600Z...DISSIPATED $$ FORECASTER STEWART |
