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| #373138 (Received by flhurricane at: 10:41 AM 02.Sep.2010) TCDAT4 TROPICAL DEPRESSION GASTON DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092010 1100 AM AST THU SEP 02 2010 METEOSAT-9 VISIBLE AND INFRARED IMAGES SHOW THAT DEEP CONVECTION ASSOCIATED WITH GASTON HAS DECREASED CONSIDERABLY AND IS LIMITED TO A FRAGMENTED BAND OVER THE WESTERN AND NORTHERN PORTION OF THE CIRCULATION. THE PIRATA PREDICTION AND RESEARCH BUOY 13008 LOCATED ABOUT 80 N MI NORTH-NORTHEAST OF THE CENTER HAS BEEN ONLY AVERAGING AROUND 17 KT DURING THE PAST 6 HOURS. DVORAK SATELLITE INTENSITY ESTIMATES HAVE DECREASED TO 30 KT FROM BOTH TAFB AND SAB. BASED ON THESE DATA...GASTON IS LOWERED TO TROPICAL DEPRESSION STATUS. ALTHOUGH THE UPPER WIND PATTERN IS FORECAST TO BE CONDUCIVE FOR STRENGTHENING...THE RATHER DRY AND STABLE THERMODYNAMIC ENVIRONMENT DOMINATING THE EASTERN TROPICAL ATLANTIC SHOULD ONLY PERMIT SLOW INTENSIFICATION. A NATIONAL SCIENCE FOUNDATION G-V AIRCRAFT IS CURRENTLY ENROUTE ON A PREDICT RESEARCH MISSION TO SAMPLE THE SURROUNDING ENVIRONMENT. THE OFFICIAL INTENSITY FORECAST FOLLOWS THE ICON CONSENSUS MODEL...AND IS CLOSE TO THE SHIPS AND LGEM MODELS AT DAYS 4 AND 5. GASTON IS MOVING A LITTLE SLOWER AND TO THE RIGHT OF THE PREVIOUS ADVISORY...AROUND 290/6...IN RESPONSE TO A MID- TO UPPER-LEVEL HIGH AMPLITUDE TROUGH SITUATED ALONG 38W AND TO THE NORTH OF THE TROPICAL CYCLONE. THE LARGE-SCALE MODELS AGREE ON A CONTINUED SLOW WEST-NORTHWESTWARD MOTION WITHIN THE WEAK EASTERLY STEERING FLOW INFLUENCED BY THE AFOREMENTIONED TROUGH THROUGH ABOUT 36 HOURS. AFTERWARDS...THE DYNAMICAL MODELS INDICATE THAT THE SUBTROPICAL RIDGE WILL BUILD EASTWARD OVER THE CENTRAL ATLANTIC THROUGH THE END OF THE PERIOD WHICH WOULD INFLUENCE GASTON TO MOVE GENERALLY WESTWARD AT A SLIGHTLY QUICKER PACE. THE NHC OFFICIAL FORECAST IS A LITTLE TO THE RIGHT OF THE PREVIOUS TRACK AND IS BASED ON A COMPROMISE OF ALL OF THE DYNAMICAL MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 02/1500Z 14.0N 38.9W 30 KT 12HR VT 03/0000Z 14.1N 39.7W 30 KT 24HR VT 03/1200Z 14.3N 40.7W 35 KT 36HR VT 04/0000Z 14.5N 42.0W 45 KT 48HR VT 04/1200Z 14.7N 43.3W 50 KT 72HR VT 05/1200Z 15.0N 46.5W 60 KT 96HR VT 06/1200Z 15.5N 51.0W 70 KT 120HR VT 07/1200Z 16.0N 56.0W 85 KT $$ FORECASTER ROBERTS/PASCH |
