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| #130748 (Received by flhurricane at: 11:03 AM 09.May.2007) TCDAT1 SUBTROPICAL STORM ANDREA DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012007 1100 AM EDT WED MAY 09 2007 AN AIR FORCE RECONNAISSANCE PLANE HAS BEEN INVESTIGATING THE LOW PRESSURE SYSTEM OFF THE SOUTHEAST U.S. COAST SINCE EARLY THIS MORNING. THE INITIAL LEG OF THE MISSION WAS FLOWN AT 300 MB FROM WEST TO EAST OVER THE CIRCULATION CENTER...AND SEVERAL DROPSONDES WERE RELEASED. THE TEMPERATURE PROFILES REVEAL A RATHER FLAT THERMAL CROSS-SECTION...NOT INDICATING A DISCERNIBLE WARM OR COLD CORE AT ANY VERTICAL LEVEL. THE WIND PROFILES...HOWEVER...SHOW WINDS INCREASING WITH HEIGHT IN THE WESTERN HALF OF THE CIRCULATION AND DECREASING WITH HEIGHT IN THE EASTERN HALF. GOES IMAGERY INDICATES THAT...COMPARED TO YESTERDAY...THE THUNDERSTORM ACTIVITY HAS CONSOLIDATED CLOSER TO THE CENTER...BUT PRIMARILY IN THE EASTERN SEMICIRCLE. THERE IS ALSO A SLIGHT HINT OF UPPER-LEVEL OUTFLOW WHICH WAS COMPLETELY ABSENT YESTERDAY...BUT THE SYSTEM REMAINS EMBEDDED WITHIN A LARGE DEEP-LAYER TROUGH. ALSO...THE RADIUS OF MAXIMUM WINDS HAS CONTRACTED FROM MORE THAN 100 N MI YESTERDAY TO ABOUT 50-60 N MI THIS MORNING. BASED ON THE HYBRID STRUCTURE OF THE SYSTEM...ADVISORIES ARE BEING INITIATED ON SUBTROPICAL STORM ANDREA. THE 40 KT INITIAL INTENSITY IS BASED ON AN EARLY MORNING QUIKSCAT PASS AND RECENT AIRCRAFT DATA FROM 850 MB. THE INITIAL MOTION IS SLOW AND GENERALLY WESTWARD...ABOUT 270 DEGREES AT 4 KT. SINCE ANDREA IS ESSENTIALLY TRAPPED WITHIN A MIDDLE- TO UPPER-LEVEL TROUGH THAT THE DYNAMICAL MODELS FORECAST TO NOT MOVE MUCH DURING THE NEXT FEW DAYS...ANDREA WILL PROBABLY CONTINUE TO MOVE SLOWLY...BUT IN THE GENERAL DIRECTION OF THE NORTHEAST FLORIDA COAST. THE OFFICIAL FORECAST GENERALLY FOLLOWS THE SCENARIO PAINTED BY ALL OF THE MODELS...TAKING THE SYSTEM SLOWLY SOUTHWESTWARD AND THEN SOUTHWARD DURING THE NEXT 3 DAYS OR SO. NONE OF THE MODELS BRING ANDREA INLAND...AND NEITHER DOES THE OFFICIAL FORECAST. ANDREA IS CURRENTLY OVER SEA-SURFACE TEMPERATURES OF NO MORE THAN ABOUT 25 CELSIUS...AND THEY WILL NOT GET ANY WARMER ALONG THE FORECAST TRACK. THEREFORE A SLOW WEAKENING TREND IS ANTICIPATED AND THE OFFICIAL FORECAST SHOWS DISSIPATION NEAR THE COAST IN LESS THAN FIVE DAYS. HOWEVER...SINCE ANDREA MIGHT BRING WINDS OF TROPICAL STORM FORCE TO THE COAST...A TROPICAL STORM WATCH HAS BEEN ISSUED. FORECAST POSITIONS AND MAX WINDS INITIAL 09/1500Z 30.8N 79.3W 40 KT 12HR VT 10/0000Z 30.6N 79.9W 40 KT 24HR VT 10/1200Z 30.2N 80.6W 35 KT 36HR VT 11/0000Z 29.8N 81.0W 35 KT 48HR VT 11/1200Z 29.6N 81.0W 30 KT 72HR VT 12/1200Z 29.5N 81.0W 25 KT 96HR VT 13/1200Z 29.5N 81.0W 25 KT...DISSIPATING 120HR VT 14/1200Z...DISSIPATED $$ FORECASTER KNABB |
