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#3798 (Received by flhurricane at: 11:07 AM 04.Aug.2004) TCDAT2 TROPICAL DEPRESSION TWO DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT WED AUG 04 2004 AN AIR FORCE RECONNAISSANCE AIRCRAFT INVESTIGATING THE DEPRESSION FOUND A VERY SHARP WIND SHIFT AND SOME SOUTH-SOUTHWESTLY WINDS AT 2500 FT...BUT WAS NOT ABLE TO CLOSE OFF A CIRCULATION. WIND REPORTS IN THE WINDWARD ISLANDS THIS MORNING WERE ALSO MORE SUGGESTIVE OF A TROPICAL WAVE STRUCTURE. WHILE STRICTLY SPEAKING THIS SYSTEM IS NOT CURRENTLY A TROPICAL CYCLONE...WE ARE ELECTING TO MAINTAIN ADVISORIES THIS MORNING. MOST OF THE DYNAMICAL MODEL GUIDANCE INDICATES THAT THE SYSTEM WILL SOON SLOW DOWN AND TURN TO THE NORTHWEST...AND IF THIS OCCURS A CLOSED CIRCULATION COULD RE-DEVELOP. THE INITIAL MOTION REMAINS 275/22. THE SYSTEM IS ON THE SOUTH SIDE OF A LOW TO MID LEVEL RIDGE...WHICH LARGE SCALE-MODELS FORECAST SHOULD WEAKEN AS AN UNSEASONABLY STRONG DEEP-LAYER TROUGH DEVELOPS OVER THE EASTERN UNITED STATES AND WESTERN ATLANTIC. THIS SUGGESTS THE SYSTEM SHOULD SLOW AND TURN NORTHWESTWARD...AND THEN POSSIBLY NORTHWARD LATER IN THE FORECAST PERIOD. THE MORE SOPHISTICATED GFDL AND GLOBAL MODELS REMAIN IN GOOD AGREEMENT ON THIS TURN TO THE NORTHWEST AND THEN NORTH...ALTHOUGH THEY HAVE BEEN GENERALLY TRENDING WESTWARD. THE SIMPLER STEERING GUIDANCE...SUCH AS THE BAM MODELS...KEEP THE SYSTEM ON MORE OF A WEST-NORTHWESTERLY TRACK. A WEAKER OR DISSIPATING SYSTEM WOULD BE MORE LIKELY TO FOLLOW THIS LATTER ALTERNATIVE. THE OFFICIAL FORECAST IS SHIFTED A LITTLE WEST OF THE PREVIOUS ADVISORY BUT BASICALLY IS CONSISTENT WITH THE GLOBAL MODEL GUIDANCE. THIS IS A VERY LOW CONFIDENCE FORECAST. THE OFFICIAL INTENSITY FORECAST IS LESS AGGRESSIVE THAN THE PREVIOUS ONE. THERE IS SOUTHWESTERLY SHEAR AHEAD OF THE DEPRESSION...AND THE CURRENT TRACK FORECAST TAKES THE SYSTEM OVER THE MOUNTAINOUS TERRAIN OF HISPANIOLA. THIS FORECAST PRESUMES...OF COURSE...THAT THE DEPRESSION DOES NOT DISSIPATE LATER TODAY. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 04/1500Z 13.8N 62.7W 30 KT 12HR VT 05/0000Z 14.5N 65.4W 30 KT 24HR VT 05/1200Z 15.6N 68.2W 35 KT 36HR VT 06/0000Z 17.5N 70.5W 40 KT 48HR VT 06/1200Z 20.0N 71.5W 30 KT 72HR VT 07/1200Z 25.0N 72.0W 35 KT 96HR VT 08/1200Z 29.0N 71.0W 40 KT 120HR VT 09/1200Z 34.0N 68.0W 45 KT |