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| #37088 (Received by flhurricane at: 11:03 PM 02.Aug.2005) TCDAT3 TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT TUE AUG 02 2005 THE UPPER LEVEL LOW TO THE SOUTHWEST OF THE DEPRESSION CONTINUES TO IMPOSE SOUTHERLY SHEAR... LEAVING MUCH OF THE LOW LEVEL CIRCULATION EXPOSED. THE PRIMARY CONCENTRATION OF CONVECTION HAS BEEN PERSISTING NORTH OF THE CENTER... WITH A DISJOINTED BAND OF CONVECTION EXTENDING TO THE SOUTHEAST. LACKING ANY OTHER SOURCE OF RELEVANT DATA THIS EVENING... THE CURRENT INTENSITY HINGES ON SUBJECTIVE INTERPRETATION OF GOES INFRARED IMAGERY. THE LATEST DVORAK INTENSITY ESTIMATES ARE 25 KT FROM TAFB BASED ON THE CURVED BANDING... AND 25 KT FROM SAB AND AFWA BASED ON THE SUBTROPICAL APPEARANCE OF THE CLOUD PATTERN. IT IS POSSIBLE THAT THE MAXIMUM WINDS ARE ACTUALLY NEAR TROPICAL STORM STRENGTH SINCE THE LOW LEVEL CENTER APPEARS TO BE JUST A SHORT DISTANCE SOUTH OF THE CONCENTRATED CONVECTION... PERHAPS WORTHY OF A T2.5/35 KT DVORAK CLASSIFICATION USING A SHEAR PATTERN. HOWEVER... THERE IS SUFFICIENT UNCERTAINTY IN THE LOCATION OF THE LOW LEVEL CENTER TO COMPROMISE BETWEEN ALL OF THESE POSSIBILITIES AND MAINTAIN THE INTENSITY AT 30 KT. THE INITIAL MOTION ESTIMATE IS 015/8... CONSTRUCTED WITH THE HELP OF A 01Z SSMI OVERPASS... WHICH A LITTLE SLOWER THAN THE PREVIOUS ADVISORY AND WITH A SLIGHTLY GREATER NORTHEASTERLY COMPONENT. THIS APPEARS TO BE THE START OF THE TURN TOWARD THE NORTHEAST AHEAD OF A MIDLATITUDE SHORTWAVE TROUGH EMERGING OFF THE UNITED STATES EAST COAST. EVEN AFTER THAT TROUGH PASSES BY THE TROPICAL CYCLONE... PERSISTENT WESTERLIES SHOULD CONTINUE TO INDUCE AN EASTWARD MOTION LATER IN THE FORECAST PERIOD. THE DYNAMICAL MODELS INITIALIZE AND FORECAST THE CIRCULATION OF THE DEPRESSION IN A VARIETY OF WAYS... NONE OF WHICH APPEAR TO BE COMPLETELY CONSISTENT WITH RECENT MOTION TRENDS. THE NEW OFFICIAL FORECAST IS A LITTLE SLOWER THAN AND TO THE RIGHT OF THE PREVIOUS ADVISORY... MAINLY TO BLEND WITH THE SLOWER GFDL AND NOGAPS SOLUTIONS. THE UPPER LEVEL LOW TO THE SOUTHWEST OF THE DEPRESSION IS EXPECTED TO ALSO MOVE EAST BUT SHEAR OUT DURING THE NEXT 2-3 DAYS... BUT THIS WILL LEAVE THE TROPICAL CYCLONE IN A WESTERLY SHEAR ENVIRONMENT SOMEWHAT PROHIBITIVE FOR TOO MUCH STRENGTHENING. HOWEVER...THE SHEAR COULD BE JUST WEAK ENOUGH... AND THE OCEAN WARM ENOUGH... TO ALLOW THE SYSTEM TO REMAIN A TROPICAL STORM THROUGH ABOUT DAY THREE. THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IS A COMPROMISE BETWEEN THE GFDL AND SHIPS GUIDANCE. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 03/0300Z 29.4N 68.5W 30 KT 12HR VT 03/1200Z 30.4N 67.9W 40 KT 24HR VT 04/0000Z 31.7N 66.2W 45 KT 36HR VT 04/1200Z 32.8N 63.9W 40 KT 48HR VT 05/0000Z 33.6N 61.1W 35 KT 72HR VT 06/0000Z 34.0N 57.0W 35 KT 96HR VT 07/0000Z 34.5N 54.0W 30 KT 120HR VT 08/0000Z 35.0N 51.0W 30 KT |
