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| #463806 (Received by flhurricane at: 4:56 AM 03.Oct.2011) TCDAT1 TROPICAL STORM OPHELIA DISCUSSION NUMBER 43 NWS NATIONAL HURRICANE CENTER MIAMI FL AL162011 500 AM AST MON OCT 03 2011 THE SATELLITE PRESENTATION OF OPHELIA HAS CONTINUED TO DETERIORATE THIS MORNING...AND THE CYCLONE IS QUICKLY LOSING ITS TROPICAL CHARACTERISTICS OVER WATER TEMPERATURES BETWEEN 10-15 CELSIUS. THERE REMAINS A SMALL AREA OF MODERATE CONVECTION WITH CLOUD TOPS COLDER THAN -50C JUST NORTHEAST OF THE ALLEGED CENTER...BUT THE AREAL COVERAGE OF THIS CONVECTION HAS BEEN RAPIDLY SHRINKING. HOWEVER...A 03/0556Z AMSU OVERPASS STILL INDICATED A VERTICALLY STACKED WARM CORE THROUGH AT LEAST THE 250/200 MB LEVEL...AND THAT IS THE JUSTIFICATION FOR MAINTAINING OPHELIA AS A TROPICAL CYCLONE ON THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 055/37 KT...BASED ON EXTRAPOLATION...CONVENTIONAL SATELLITE FIXES...AND A 03/0621 AMSR-E MICROWAVE OVERPASS. OPHELIA IS EXPECTED TO MOVE NORTHEASTWARD THIS MORNING AND MAKE LANDFALL ALONG THE AVALON PENINSULA BETWEEN ROUGHLY 10-12Z THIS MORNING. VERY COLD WATER BENEATH OPHELIA AND INCREASING VERTICAL WIND SHEAR IN EXCESS OF 40 KT SHOULD RESULT IN COMPLETE TRANSITION TO AN EXTRATROPICAL LOW PRESSURE SYSTEM BY 18Z...IF NOT SOONER. THE OFFICIAL TRACK FORECAST IS DOWN THE MIDDLE OF THE TIGHTLY PACKED NHC MODEL GUIDANCE SUITE...AND LIES CLOSE TO THE GUIDANCE PROVIDED BY THE NOAA OCEAN PREDICTION CENTER. A 03/0027Z ASCAT OVERPASS INDICATED A LARGE SWATH OF 50-55 KT WIND VECTORS IN THE EAST AND SOUTHEAST OCTANTS OF THE CIRCULATION. GIVEN THE KNOWN LOW BIAS OF THIS REMOTE SENSING INSTRUMENT...OPHELIA WAS KEPT AS A 65-KT HURRICANE AT 06Z...AND IS NOW A 60-KT TROPICAL STORM DUE TO THE LOSS OF CENTRAL DEEP CONVECTION IN THE REGION OF STRONGEST WINDS NOTED IN THE ASCAT DATA. CANADIAN RADAR DATA FROM THE AVALON PENINSULA INDICATE THE RAIN SHIELD AHEAD OF THE CENTER IS MOSTLY STRATIFORM IN NATURE...FURTHER INDICATING THAT OPHELIA IS UNDERGOING EXTRATROPICAL TRANSITION. OPHELIA SHOULD CONTINUE TO WEAKEN OVER COLDER WATER AND EVENTUALLY MERGE WITH A FRONTAL SYSTEM IN 24-36 HOURS. THE OFFICIAL INTENSITY FORECAST AND FORECAST WIND RADII ARE BASED ON GUIDANCE PROVIDED BY THE NOAA OCEAN PREDICTION CENTER. ADVISORY WIND RADII WERE ADJUSTED BASED ON A 03/0027Z ASCAT OVERPASS AND SURROUNDING SURFACE OBSERVATIONS. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 46.5N 54.2W 60 KT 70 MPH 12H 03/1800Z 49.1N 48.4W 50 KT 60 MPH...POST-TROP/EXTRATROP 24H 04/0600Z 51.0N 38.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 36H 04/1800Z 53.0N 28.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 05/0600Z...ABSORBED BY FRONTAL SYSTEM $$ FORECASTER STEWART |
