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| #45698 (Received by flhurricane at: 11:03 AM 13.Sep.2005) TCDAT1 TROPICAL STORM OPHELIA DISCUSSION NUMBER 29 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT TUE SEP 13 2005 DATA FROM SATELLITES...DOPPLER RADARS...AND AN AIR FORCE RECONNAISSANCE AIRCRAFT INDICATE OPHELIA HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING AND IS JUST BELOW HURRICANE STRENGTH. THE HIGHEST RECON 700 MB FLIGHT-LEVEL HAS BEEN 66 KT IN THE NORTHEAST QUADRANT. DOPPLER VELOCITY DATA FROM WILMINGTON HAS BEEN RUNNING 67-70 KT BETWEEN 10000 TO 12000 FEET IN THE NORTHEAST QUADRANT... JUST TO THE NORTHWEST OF THE RECON MAX WIND REPORT. THESE VALUES WOULD SUPPORT 59-63 KT SURFACE WINDS...AND THE INITIAL INTENSITY IS A BLEND OF THESE VALUES. THE INITIAL MOTION ESTIMATE IS 330/03 OVER THE PAST 9-12 HOURS. A SMALL INNER-CORE CIRCULATION WITH CONVECTION HAS BEEN ROTATING CYCLONICALLY AROUND THE INSIDE OF THE LARGER RADIUS OF MAXIMUM WINDS. THIS HAS RESULTED IN SPITS AND SPURTS OF FORWARD MOTION... INCLUDING SMALL LOOPS. HOWEVER...THE LARGER CIRCULATION AND PRESSURE FIELD APPEAR TO BE MOVING SLOWLY BUT STEADILY TOWARD THE NORTH CAROLINA COAST. THE LATEST 12Z UPPER-AIR DATA INDICATES A SMALL MID- TO UPPER-LEVEL HIGH PRESSURE CELL HAS MOVED FROM WEST VIRGINIA TO NEW JERSEY DURING THE PAST 24 HOURS...DURING WHICH TIME THE HEIGHTS HAVE DECREASED BY AT LEAST 30-40 METERS. AS THIS FEATURE CONTINUES TO MOVE EAST-NORTHEASTWARD OFF THE NORTHEAST U.S. COAST...THE STEERING FLOW SHOULD BECOME MORE SOUTHERLY AND ALLOW OPHELIA TO GRADUALLY LIFT NORTHWARD DURING THE NEXT 24 HOURS. AFTER THAT...THE NHC MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON THE CYCLONE TURNING SLOWLY NORTHEASTWARD AND CROSSING THE NORTH CAROLINA OUTER BANKS IN ABOUT 48 HOURS BEFORE ACCELERATING EAST-NORTHEASTWARD AHEAD OF A STRONG SHORTWAVE TROUGH AND FRONTAL SYSTEM. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE PREVIOUS TRACK THROUGH 48 HOURS...AND THEN FASTER AND A LITTLE TO THE RIGHT AFTER THAT. THIS IS CONSISTENT WITH BUT TO THE RIGHT OF THE NHC MODEL CONSENSUS DUE TO MORE WESTERLY MID-LEVEL FLOW ACTING TO DRIVE THE CYCLONE MORE TO THE EAST AT HIGHER LATITUDES AT DAYS 4 AND 5. THE INNER CORE OF OPHELIA IS MOVING OVER THE WARMER GULFSTREAM WHERE SSTS ARE 82F-83F. THE WARMER WATER HAS LIKELY HELPED TO GENERATE SOME MODERATE CONVECTION AROUND THE WIND CENTER. HOWEVER...THERE IS STILL A LOT OF DRY AIR IN THE INNER REGION THAT HAS TO BE MIXED OUT BEFORE ANY SIGNIFICANT STRENGTHENING CAN OCCUR. ONCE OPHELIA NEARS THE COAST OF THE CAROLINAS WHERE SSTS DROP BY ABOUT 3F-5F...THERE MAY BE SOME EROSION OF THE INNER CORE CONVECTION. HOWEVER...GIVEN THE LARGE SIZE OF THE RADIUS IF MAXIMUM WINDS...ONLY SLOW INTENSITY CHANGES UP OR DOWN SHOULD OCCUR BEFORE...DURING...AND AFTER LANDFALL. UPPER-LEVEL OUTFLOW IS EXPECTED TO REMAIN QUITE FAVORABLE FOR THE NEXT 36-48 HOURS...SO SOME MODEST STRENGTHENING IS POSSIBLE AND OPHELIA COULD PEAK AT 70 KT BEFORE LANDFALL OCCUR. ONCE OPHELIA CLEARS THE OUTER BANKS...INCREASING WESTERLY SHEAR SHOULD INDUCE SLOW WEAKENING UNTIL THE CYCLONE TRANSITIONS INTO AN EXTRATROPICAL LOW PRESSURE SYSTEM OVER THE COLD WATERS OF THE NORTH ATLANTIC. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 13/1500Z 32.3N 78.0W 60 KT 12HR VT 14/0000Z 32.9N 78.1W 65 KT 24HR VT 14/1200Z 33.9N 77.7W 65 KT 36HR VT 15/0000Z 34.9N 76.9W 65 KT...INLAND 48HR VT 15/1200Z 35.4N 75.7W 65 KT...INLAND/PAMLICO SOUND 72HR VT 16/1200Z 36.7N 72.7W 60 KT 96HR VT 17/1200Z 41.0N 65.5W 55 KT...BECOMING EXTRATROPICAL 120HR VT 18/1200Z 47.0N 53.5W 45 KT...EXTRATROPICAL |
