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| #461307 (Received by flhurricane at: 10:56 AM 23.Sep.2011) TCDAT1 TROPICAL STORM OPHELIA DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL162011 1100 AM AST FRI SEP 23 2011 THE SATELLITE APPEARANCE OF OPHELIA HAS CONTINUED TO DEGRADE AND THE SYSTEM IS LOOKING LESS AND LESS LIKE A TROPICAL CYCLONE. DRY AIR COUPLED WITH MODERATE TO STRONG SOUTH-SOUTHWESTERLY WIND SHEAR HAS ERODED NEARLY ALL OF THE INNER CORE CONVECTION...AND WHAT DEEP CONVECTION THAT DOES EXIST IS OCCURRING IN A RAGGED BAND MORE THAN 200 NMI EAST THROUGH SOUTH OF THE CENTER. THE INITIAL INTENSITY IS DECREASED TO 35 KT BASED ON AN EARLIER WIND REPORT OF 31 KT FROM NOAA BUOY 41041 LOCATED WELL EAST OF THE CENTER. NOAA BUOY 41040 JUST WEST OF THE CENTER HAS NOT SHOWN SIGNS OF THE SURFACE WINDS BACKING AROUND TO A WESTERLY DIRECTION...WHICH SUGGESTS THAT OPHELIA MIGHT JUST BE A SHARP OPEN WAVE. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT WILL INVESTIGATE THE CYCLONE THIS AFTERNOON BETWEEN 18-00Z TO SEE IF OPHELIA HAS A CLOSED SURFACE CIRCULATION. THE INITIAL MOTION IS 280/14. SMOOTHING THROUGH ALL OF THE WIGGLES AND WOBBLES...CAUSED BY BRIEF CONVECTIVE BURSTS NEAR THE CENTER... OVER THE PAST 48 HOURS ALSO YIELDS A MOTION VECTOR OF 280 DEGREES. AS CONTINUED STRONG VERTICAL SHEAR AND DRY AIR ENTRAINMENT TAKE THEIR TOLL ON THE CONVECTIVE STRUCTURE AND ORGANIZATION OF OPHELIA...THE VERTICAL DEPTH OF THE CYCLONE IS EXPECTED TO BECOME INCREASINGLY SHALLOW. THE RESULT IS THAT THE CYCLONE SHOULD BE STEERED MORE WESTWARD LIKE THE ECMWF AND UKMET ARE FORECASTING...AND LESS POLEWARD LIKE THE MORE ROBUST GFDL AND HWRF MODELS ARE INDICATING. ASSUMING OPHELIA STILL EXISTS BY DAYS 4 AND 5...A TURN TOWARD THE NORTHWEST AND NORTH IS EXPECTED AS THE CYCLONE ROUNDS THE WESTERN PERIPHERY OF THE BERMUDA HIGH AND LIFTS OUT POLEWARD AHEAD OF AN UPPER-LEVEL LOW EAST OF THE BAHAMAS. THE OFFICIAL FORECAST TRACK IS TO THE LEFT OF THE PREVIOUS TRACK AND THE CONSENSUS MODELS DUE TO THE UNREALISTIC NORTHWARD TRACK OF THE HWRF MODEL...AND LIES ALONG THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE NEAR A BLEND OF THE ECMWF...UKMET...AND SHALLOW BAM MODELS. THE 25-30 KT OF SOUTHWESTERLY TO WESTERLY VERTICAL SHEAR IS NOT FORECAST TO ABATE FOR THE NEXT 4 DAYS OR SO...ALL THE WHILE THE CYCLONE MOVES INTO AN EVEN DRIER AIR MASS. IT IS...THEREFORE... POSSIBLE THAT OPHELIA COULD DEGENERATE INTO A REMNANT LOW OR EVEN AN OPEN WAVE BY 48 HOURS LIKE THE STATISTICAL-DYNAMICAL MODELS SHIPS AND LGEM ARE FORECASTING. HOWEVER...GIVEN THE RATHER LARGE CIRCULATION OF OPHELIA AND THAT SSTS OF NEAR 29C LIE AHEAD OF THE CYCLONE...THE OFFICIAL FORECAST CALLS FOR OPHELIA TO MAINTAIN SOME CONVECTION AND AT LEAST TROPICAL DEPRESSION STATUS THROUGH DAY 4. BY DAY 5...SOME SLIGHT INTENSIFICATION IS POSSIBLE ON AS THE SHEAR DECREASES AND OPHELIA MOVES UNDER OR NEAR A SMALL UPPER-LEVEL ANTICYCLONE. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 14.6N 52.6W 35 KT 40 MPH 12H 24/0000Z 15.6N 54.6W 35 KT 40 MPH 24H 24/1200Z 16.8N 56.9W 30 KT 35 MPH 36H 25/0000Z 17.9N 58.8W 30 KT 35 MPH 48H 25/1200Z 19.1N 60.9W 30 KT 35 MPH 72H 26/1200Z 21.2N 64.3W 30 KT 35 MPH 96H 27/1200Z 23.0N 66.5W 30 KT 35 MPH 120H 28/1200Z 25.5N 67.5W 35 KT 40 MPH $$ FORECASTER STEWART |
