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| #365615 (Received by flhurricane at: 4:34 AM 03.Aug.2010) TCDAT4 TROPICAL STORM COLIN DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042010 500 AM EDT TUE AUG 03 2010 THE TROPICAL CYCLONE HAS BECOME BETTER ORGANIZED OVER THE PAST SEVERAL HOURS. ENHANCED INFRARED SATELLITE IMAGES SHOW A CURVED BAND WRAPPING HALFWAY AROUND THE CIRCULATION OVER THE WESTERN SEMICIRCLE. DVORAK DATA T-NUMBERS ARE 2.5 FROM BOTH TAFB AND SAB SUPPORTING A CURRENT INTENSITY ESTIMATE OF 35 KT. THEREFORE THE SYSTEM IS BEING NAMED AT THIS TIME. COLIN IS EXPECTED TO BE IN AN ENVIRONMENT CONDUCIVE FOR SOME STRENGTHENING...WITH MODERATE TO WEAK VERTICAL SHEAR AND ANTICYCLONIC UPPER-LEVEL FLOW...FOR THE NEXT 36 HOURS OR SO. THEREAFTER...INCREASING WESTERLY SHEAR ASSOCIATED WITH AN UPPER-LEVEL LOW OVER THE SOUTHWESTERN NORTH ATLANTIC SHOULD BEGIN TO IMPACT THE STORM. THE OFFICIAL FORECAST CALLS FOR MODEST STRENGTHENING DURING THE NEXT 36 HOURS FOLLOWED BY A LEVELING OFF OF INTENSITY THEREAFTER. THIS IS SIMILAR TO THE LATEST GFDL MODEL FORECAST AND NOT TOO DISSIMILAR TO THE PREVIOUS NHC FORECAST. NONE OF THE DYNAMICAL OR STATISTICAL/DYNAMICAL INTENSITY GUIDANCE BRINGS COLIN TO HURRICANE STRENGTH OVER THE NEXT 5 DAYS. CENTER FIXES SHOW THAT THE STORM CONTINUES TO MOVE BRISKLY TOWARD THE WEST-NORTHWEST...AND THE INITIAL MOTION ESTIMATE REMAINS AT 285/20. AT THIS TIME...THE STEERING FOR COLIN IS BEING PROVIDED DUE TO A SUBTROPICAL RIDGE TO THE NORTH AND A LOW- TO MID-TROPOSPHERIC EASTERLY JET. THIS RELATIVELY FAST STEERING CURRENT SHOULD MORE OR LESS PREVAIL FOR THE NEXT COUPLE OF DAY OR SO. THEREAFTER...THE TROPICAL CYCLONE IS LIKELY TO APPROACH A WEAKNESS IN THE SUBTROPICAL RIDGE. THIS WOULD CAUSE A GRADUAL TURN TO THE RIGHT ALONG WITH A DECREASING FORWARD SPEED. THE TRACK GUIDANCE MODELS ARE IN FAIRLY GOOD AGREEMENT OVER THE NEXT 36 HOURS. AFTER THAT FORECAST TIME...THE MODELS BECOME MODERATELY DIVERGENT WITH THE GFS AND ECMWF ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE AND THE GFDL AND HWRF ON THE RIGHT. THE OFFICIAL TRACK FORECAST IS ROUGHLY IN THE MIDDLE OF THE ENVELOPE...FAIRLY CLOSE TO THE DYNAMICAL MODEL CONSENSUS...AND VERY CLOSE TO THE PREVIOUS NHC FORECAST. OBSERVATIONS FROM NOAA DATA BUOY 41041 OVER THE CENTRAL TROPICAL ATLANTIC INDICATE THAT COLIN IS A SMALL TROPICAL STORM...AND THE WIND RADII SHOWN IN THE ADVISORY MIGHT BE GENEROUS. INTERESTS IN THE NORTHERN LEEWARD ISLANDS SHOULD FOLLOW THE PROGRESS OF COLIN. AT THIS TIME...BASED ON THE FORECAST TRACK...WIND FIELD...AND REASONABLE UNCERTAINTIES...NO TROPICAL STORM WATCHES OR WARNINGS ARE REQUIRED. FORECAST POSITIONS AND MAX WINDS INITIAL 03/0900Z 14.0N 47.2W 35 KT 12HR VT 03/1800Z 15.1N 50.3W 40 KT 24HR VT 04/0600Z 16.8N 54.5W 45 KT 36HR VT 04/1800Z 18.6N 58.3W 50 KT 48HR VT 05/0600Z 20.6N 61.5W 50 KT 72HR VT 06/0600Z 24.5N 66.5W 50 KT 96HR VT 07/0600Z 28.0N 68.5W 50 KT 120HR VT 08/0600Z 31.0N 69.5W 50 KT $$ FORECASTER PASCH |
