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#105981 (Received by flhurricane at: 11:17 PM 24.Aug.2006) TCDAT5 TROPICAL DEPRESSION FIVE DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052006 1100 PM EDT THU AUG 24 2006 LATEST INFRARED SATELLITE IMAGERY INDICATES THE TROPICAL CYCLONE HAS MAINTAINED CONVECTION IN A SOMEWHAT SHEARED ENVIRONMENT. A BLEND OF DVORAK CLASSIFICATIONS YIELDS A DATA T-NUMBER OF 2.0 OR 30 KT. BASED UPON THIS INFORMATION AS WELL AS LITTLE CHANGE IN THE CONVECTIVE ORGANIZATION...THE CYCLONE IS KEPT AS A TROPICAL DEPRESSION WITH 30 KT MAXIMUM WINDS. THE INITIAL MOTION IS 280/17...WHICH IS AN AVERAGE OF THE LAST SIX HOURS. THE CYCLONE IS CURRENTLY BEING STEERED ON A WESTERLY TRACK BY A LOW- TO MID-LEVEL RIDGE STRETCHING ACROSS THE SOUTHWESTERN ATLANTIC. THE UKMET AND NOGAPS MODELS MAINTAIN THIS RIDGE TO THE NORTH OF THE DEPRESSION AND TAKE A RELATIVELY WEAK SYSTEM ON A STRAIGHT WESTWARD TRACK. THE GFS AND GFDL MODELS FORECAST A WEAKNESS IN THE RIDGE TO THE NORTH AND FORECAST A STRONGER CYCLONE TO BE IN THE VICINITY OF WESTERN CUBA IN 5 DAYS. THE OFFICIAL TRACK FORECAST IS NUDGED SLIGHTLY TO THE NORTH OF THE PREVIOUS ADVISORY...TOWARD THE GFS AND GFDL SOLUTIONS. THE INTENSITY FORECAST IS HIGHLY CONTINGENT UPON A COMPLICATED UPPER-LEVEL PATTERN FOR WHICH THE GLOBAL MODELS PROVIDE DIFFERING SOLUTIONS. AN UPPER-LEVEL LOW OVER THE WESTERN CARIBBEAN IS FORECAST TO SPLIT FROM A SHEAR AXIS CURRENTLY STRETCHED ALONG 25N IN THE WESTERN ATLANTIC. THE UKMET AND NOGAPS MODELS KEEP THE UPPER-LEVEL LOW INTACT AND MOVE IT WESTWARD OVER THE NEXT 3 TO 5 DAYS TO THE SOUTH OF A LARGE MID-UPPER ANTICYCLONE OVER THE SOUTHEASTERN UNITED STATES. THIS SCENARIO MIGHT KEEP SOME SOUTHERLY SHEAR OVER THE TROPICAL CYCLONE. ON THE OTHER HAND...THE GFS AND GFDL MODELS MOVE THE UPPER-LEVEL LOW FASTER TO THE WEST...CREATING A MUCH WEAKER SHEAR ENVIRONMENT OVER THE WESTERN CARIBBEAN AT DAYS 3 TO 5. ALL THIS MEANS IS THAT THE INTENSITY FORECAST IS HIGHLY UNCERTAIN. BOTH THE SHIPS AND GFDL MODELS INTENSIFY THE CYCLONE TO A HURRICANE WITHIN 3 DAYS. THEREAFTER...THE GFDL MODEL WEAKENS THE SYSTEM OVER CUBA BUT THE SHIPS FORECAST CONTINUED STRENGTHENING THROUGH 5 DAYS. THE OFFICIAL INTENSITY FORECAST IS NUDGED UPWARD TOWARD THE GFDL AND SHIPS GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 25/0300Z 13.2N 63.9W 30 KT 12HR VT 25/1200Z 13.7N 66.2W 35 KT 24HR VT 26/0000Z 14.5N 68.9W 40 KT 36HR VT 26/1200Z 15.3N 71.1W 45 KT 48HR VT 27/0000Z 16.0N 73.0W 55 KT 72HR VT 28/0000Z 17.5N 77.0W 65 KT 96HR VT 29/0000Z 19.5N 81.0W 65 KT 120HR VT 30/0000Z 22.0N 85.0W 65 KT |