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| #366849 (Received by flhurricane at: 10:43 AM 07.Aug.2010) TCDAT4 TROPICAL STORM COLIN DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042010 1100 AM AST SAT AUG 07 2010 VISIBLE SATELLITE IMAGES INDICATE THAT THE CLOUD PATTERN CONTINUES TO BE DISORGANIZED AND CONSISTS OF A TIGHT SWIRL OF LOW CLOUDS WITH SOME SHAPELESS CONVECTION TO THE EAST AND SOUTHEAST OF THE CENTER. GIVEN THE CURRENT SATELLITE PRESENTATION...THE INITIAL INTENSITY HAS BEEN REDUCED TO 35 KNOTS. THESE WINDS ARE PROBABLY CONFINED TO RAINBANDS ON THE EASTERN PORTION OF THE CIRCULATION. THE STRONG WESTERLY SHEAR OBSERVED YESTERDAY HAS RELAXED A LITTLE BIT AND THE CYCLONE IS LOCATED UNDER A SMALL UPPER-LEVEL RIDGE BETWEEN TWO LARGER UPPER LEVEL LOWS. ALTHOUGH THERE ARE NO INDICATIONS THAT STRENGTHENING IS ABOUT TO OCCUR...THE OBSERVED UPPER-LEVEL PATTERN COULD ALLOW A SLIGHT INTENSIFICATION TO BEGIN LATER TODAY. BOTH THE GFDL AND HWRF MODELS INSIST ON SOME STRENGTHENING BUT IT OCCURS BY THE LATTER PART OF THE FORECAST WHEN EXTRATROPICAL TRANSITION SHOULD BEGIN. COLIN IS FORECAST TO BECOME EXTRATROPICAL BY 72 HOURS AS IT MOVES OVER COOLER WATERS. UNEXPECTEDLY...COLIN HAS BARELY MOVED DURING THE PAST FEW HOURS AS IT BECAME EMBEDDED WITHIN LIGHT STEERING CURRENTS. NONE OF THE GUIDANCE FORECAST THE CURRENT SLOW MOTION AND IN FACT...MOST OF THE MODELS INSIST ON RECURVATURE SOON AND A MOTION TOWARD THE NORTH-NORTHEAST WITH AN INCREASE IN FORWARD SPEED. THIS ACCELERATION TO THE NORTH-NORTHEAST APPEARS TO BE REALISTIC AS A LARGE TROUGH AMPLIFIES OVER THE EASTERN UNITED STATES BRINGING A STRONGER SOUTHWESTERLY STEERING FLOW OVER THE STORM. THIS IS THE SCENARIO FOLLOWED IN THE OFFICIAL FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 07/1500Z 29.0N 66.4W 35 KT 12HR VT 08/0000Z 30.7N 66.2W 35 KT 24HR VT 08/1200Z 33.0N 65.5W 40 KT 36HR VT 09/0000Z 35.5N 64.0W 45 KT 48HR VT 09/1200Z 39.0N 60.5W 50 KT 72HR VT 10/1200Z 46.5N 50.0W 50 KT...POST-TROP/EXTRATROP 96HR VT 11/1200Z 55.0N 41.5W 45 KT...POST-TROP/EXTRATROP 120HR VT 12/1200Z...ABSORBED BY A LARGE EXTRATROPICAL LOW $$ FORECASTER AVILA |
