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| #541572 (Received by flhurricane at: 10:50 AM 09.Sep.2012) TCDAT3 HURRICANE MICHAEL DISCUSSION NUMBER 26 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132012 1100 AM AST SUN SEP 09 2012 WHILE THE OVERALL SATELLITE APPEARANCE HAS NOT CHANGED MUCH THIS MORNING...THERE SEEM TO BE SOME CHANGES OCCURRING WITHIN THE INNER CORE OF MICHAEL. THE EYE HAS INCREASED IN DIAMETER FROM 10 TO 25 N MI AT THE SAME TIME CLOUD TOP TEMPERATURES HAVE WARMED...POSSIBLY INDICATIVE OF A MIXING EVENT WITHIN THE EYE. DVORAK T-NUMBERS FROM BOTH SATELLITE AGENCIES ARE AT 4.5 AT 1200 UTC...AND AN AVERAGE OF RECENT ADT VALUES IS 5.2. THE INITIAL INTENSITY IS LOWERED SLIGHTLY TO 80 KT ON THIS ADVISORY BASED ON A BLEND OF THESE DATA AND IN LIGHT OF THE RECENT STRUCTURAL CHANGES WITHIN THE INNER CORE. RECENT CENTER FIXES INDICATE THAT THE HURRICANE HAS TURNED TOWARD THE WEST...AND THE INITIAL MOTION ESTIMATE IS A SLOW 275/04. GLOBAL MODELS SHOW A POTENT SHORTWAVE TROUGH DIGGING TO THE EAST OF MICHAEL DURING THE NEXT 24-36 HOURS. WHILE THIS FEATURE SHOULD HAVE NO DIRECT EFFECT ON THE CYCLONE...RISING HEIGHTS IN THE WAKE OF THE SHORTWAVE SHOULD ALLOW FOR A SLOW WESTERLY TO WEST- NORTHWESTERLY COURSE DURING THE NEXT DAY OR SO. BY 48 HOURS... MICHAEL SHOULD TURN NORTHWARD AND THEN NORTH-NORTHEASTWARD AT AN INCREASING FORWARD SPEED AS IT REACHES THE FAST-PACED SOUTH-SOUTHWESTERLY FLOW AHEAD OF A SHARP SHORTWAVE TROUGH CROSSING THE CANADIAN MARITIMES. THE NHC TRACK FORECAST IS ADJUSTED A BIT TO THE LEFT THROUGH 48 HOURS AND SOMEWHAT TO THE EAST BY 72 HOURS...WITH THE FORECAST NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE. ALTHOUGH THE WATERS ALONG THE TRACK OF MICHAEL ARE EXPECTED TO BE WARM ENOUGH...THE CURRENT FAVORABLE ENVIRONMENT OF LIGHT SHEAR IS ABOUT TO CHANGE. WITHIN 24 HOURS...STRONG NORTHERLY WIND SHEAR OVER MICHAEL IS EXPECTED TO DEVELOP AS THE CYCLONE PASSES FROM SOUTH OF A RIDGE AXIS TO A POSITION UNDERNEATH THE OUTFLOW ASSOCIATED WITH LESLIE. ALTHOUGH THIS SHEAR SHOULD BE CONFINED TO A NARROW LAYER IN THE UPPER TROPOSPHERE...IT COULD BE OF A MAGNITUDE THAT WOULD INDUCE A FASTER WEAKENING THAN FORECAST. A BRIEF REDUCTION IN SHEAR IS POSSIBLE AFTER THIS TIME BEFORE MICHAEL ENCOUNTERS INCREASING SOUTH-SOUTHWESTERLY SHEAR ASSOCIATED WITH A STRONG MID-LATITUDE JET. A COMBINATION OF THE SHEAR AND RAPIDLY DECREASING SEA SURFACE TEMPERATURES ALONG THE TRACK SHOULD MEAN STEADY WEAKENING UNTIL THE CYCLONE BECOMES FRONTAL AROUND 72 HOURS. THE NHC INTENSITY FORECAST IS NEARLY THE SAME AS THE PREVIOUS ONE...AND IS CLOSE TO A BLEND OF SHIPS MODEL OUTPUT AND THE LATEST INTENSITY CONSENSUS AIDS. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 33.7N 43.2W 80 KT 90 MPH 12H 10/0000Z 33.8N 43.9W 80 KT 90 MPH 24H 10/1200Z 34.0N 45.5W 75 KT 85 MPH 36H 11/0000Z 35.1N 47.0W 65 KT 75 MPH 48H 11/1200Z 38.1N 47.6W 55 KT 65 MPH 72H 12/1200Z 46.5N 44.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 13/1200Z...DISSIPATED $$ FORECASTER KIMBERLAIN |
