ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM COLIN DISCUSSION NUMBER 11 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042010 1100 AM AST FRI AUG 06 2010 COLIN SHOWS A CLASSIC SHEAR PATTERN THIS MORNING WITH THE LOW-LEVEL CENTER EXPOSED TO THE WEST OF THE MAIN CONVECTIVE MASS BY 20-25 KT OF WESTERLY VERTICAL WIND SHEAR. DVORAK AND AMSU SATELLITE INTENSITY ESTIMATES HAVE NOT CHANGED SINCE THE PREVIOUS ADVISORY AND REMAIN NEAR 35 KT. BASED ON THIS...THE INITIAL INTENSITY REMAINS 40 KT...AND THIS COULD BE A LITTLE GENEROUS. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE COLIN AROUND 18Z TODAY. JUST AFTER THE PREVIOUS ADVISORY...THE CENTER OF COLIN TOOK A SHARP TURN TO THE RIGHT...AND IT HAS BEEN MOVING 065/6 FOR THE PAST SEVERAL HOURS. THIS IS LIKELY TO BE TEMPORARY...AS THE SYNOPTIC PATTERN OF HIGHER PRESSURES TO THE EAST AND LOWER PRESSURES TO THE WEST SUPPORT A MOTION TOWARD THE NORTH DURING THE NEXT 24-36 HR. THAT MOTION SHOULD BRING COLIN NORTH OF THE SUBTROPICAL RIDGE AXIS INTO THE WESTERLIES...WHICH IN TURN SHOULD CAUSE THE CYCLONE TO MOVE NORTHEASTWARD WITH AN INCREASING FORWARD SPEED. THE TRACK GUIDANCE IS IN GOOD AGREEMENT WITH THIS SCENARIO...BUT THERE REMAIN SOME SPREAD IN THE SPEED BETWEEN THE SLOWER GFS AND THE FASTER NOGAPS. THE NEW FORECAST TRACK IS NUDGED TO THE EAST BASED ON THE INITIAL POSITION AND MOTION AND IS IN BEST OVERALL AGREEMENT WITH THE UKMET AND ECMWF. SOME ADDITIONAL ADJUSTMENT MAY BE NECESSARY LATER TODAY...DEPENDING ON HOW LONG COLIN CONTINUES THE CURRENT MOTION. SHEAR FORECASTS FROM THE SHIPS AND THE DYNAMICAL MODELS SUGGEST THAT THE CURRENT SHOULD SHOULD DECREASE DURING THE NEXT 12-24 HR... ALTHOUGH THE SHIPS MODEL MAY BE OVERLY OPTIMISTIC WITH ITS FORECAST OF 11 KT OF SHEAR BY 00Z. AFTER THIS...COLIN IS LIKELY TO REMAIN IN AN ENVIRONMENT FAVORABLE FOR STRENGTHENING UNTIL IT REACHES STRONGER SHEAR IN THE MAIN BELT OF THE WESTERLIES IN ABOUT 72 HR. THE GFDL AND HWRF FORECAST COLIN TO BECOME A HURRICANE BY 72 HR... WHILE THE SHIPS AND LGEM ARE LESS AGGRESSIVE. THE FORECAST PEAK INTENSITY OF 60 KT IS A COMPROMISE BETWEEN THESE EXTREMES IN AGREEMENT WITH THE INTENSITY CONSENSUS. EXTRATROPICAL TRANSITION SHOULD BEGIN AT ABOUT 72 HR AND BE COMPLETE BY 96 HR...WITH THE DYNAMICAL MODELS FORECASTING COLIN TO REMAIN A STRONG CYCLONE THROUGH THAT PROCESS. FORECAST POSITIONS AND MAX WINDS INITIAL 06/1500Z 27.1N 66.9W 40 KT 12HR VT 07/0000Z 28.3N 66.9W 40 KT 24HR VT 07/1200Z 30.2N 66.3W 45 KT 36HR VT 08/0000Z 32.2N 65.4W 50 KT 48HR VT 08/1200Z 34.5N 64.1W 55 KT 72HR VT 09/1200Z 39.5N 60.0W 60 KT 96HR VT 10/1200Z 45.0N 52.0W 55 KT...POST-TROP/EXTRATROP 120HR VT 11/1200Z 53.0N 41.5W 50 KT...POST-TROP/EXTRATROP $$ FORECASTER BEVEN NNNN
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