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#386414 (Received by flhurricane at: 4:41 AM 30.Oct.2010) TCDAT5 HURRICANE SHARY DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL202010 500 AM AST SAT OCT 30 2010 SHARY POSES A BIT OF A CONUNDRUM THIS MORNING. THE LATEST SATELLITE IMAGES SHOW THAT DEEP CONVECTION HAS CONTINUED TO GROW AND BECOME MORE SYMMETRIC NEAR THE CENTER. IN ADDITION...TRMM PASSES FROM OVERNIGHT INDICATED THE DEVELOPMENT OF A SMALL EYE FEATURE IN THE 37-GHZ CHANNEL. WHILE DVORAK T-NUMBERS ARE HIGHER THAN EARLIER ...THEY ARE FAR FROM SUPPORTING HURRICANE INTENSITY...ALTHOUGH THESE SATELLITE ESTIMATES ARE CLEARLY NOT HANDLING THIS SYSTEM WELL. THE DEEPENING OF CONVECTION AND THE EYE FEATURE IN MICROWAVE IMAGERY SUGGEST A FURTHER ORGANIZATION OF SHARY AND AT LEAST A NOMINAL INCREASE IN WIND SPEED FROM THE 60 KT OBSERVED FROM THE AIRCRAFT. NORMALLY A 5-KT WIND ADJUSTMENT WOULD NOT REQUIRE THIS MUCH DISCUSSION...BUT A CHANGE IN STATUS DOES COMPLICATE MATTERS. IT IS HARD TO DISCOUNT THE LARGE CONVECTIVE INCREASE AND THE SIGNIFICANT IMPROVEMENT ON MICROWAVE IMAGES SINCE THE AIRCRAFT DEPARTED...THUS THE INITIAL WINDS ARE NUDGED UPWARD TO 65 KT. THIS IS A GOOD CASE OF A SMALL HURRICANE THAT WAS VERY UNLIKELY TO BE OBSERVED BEFORE THE RECENT ERA WHEN MICROWAVE SATELLITE IMAGERY WAS AVAILABLE. THE TRMM PASSES AND GEOSTATIONARY SATELLITE IMAGERY INDICATE THAT SHARY HAS ACCELERATED CONSIDERABLY AND IS NOW SPEEDING NORTHEASTWARD AT ABOUT 30 KT. THIS GENERAL TRACK IS EXPECTED TO CONTINUE WHILE THE SYSTEM REMAINS ENTRENCHED IN SOUTHWESTERLY MID-LATITUDE FLOW. A COLD FRONT RAPIDLY APPROACHING SHARY IS EXPECTED TO CAUSE THE HURRICANE TO BECOME AN EXTRATROPICAL LOW WITHIN 12 TO 24 HOURS BEFORE ABSORBING THE CYCLONE BY 36 HOURS. THE GLOBAL MODELS ARE IN GOOD AGREEMENT ON THIS TRANSITION...AND THE NEW FORECAST IS ADJUSTED TO THE RIGHT TO ACCOUNT FOR THE INITIAL MOTION AND THE LATEST TRACK GUIDANCE. SHARY SHOULD BEGIN TO WEAKEN SOON DUE TO INCREASING SHEAR AS IT MOVES OVER WATERS COOLER THAN 76F. THE INTENSITY FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS ONE AFTER ACCOUNTING FOR THE SLIGHTLY HIGHER INITIAL WINDS. FORECAST POSITIONS AND MAX WINDS INITIAL 30/0900Z 33.6N 59.4W 65 KT 12HR VT 30/1800Z 35.7N 54.6W 55 KT 24HR VT 31/0600Z 38.5N 48.0W 45 KT...POST-TROP/EXTRATROP 36HR VT 31/1800Z...ABSORBED BY A COLD FRONT $$ FORECASTER BLAKE |