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#110933 (Received by flhurricane at: 5:02 AM 15.Sep.2006) TCDAT2 HURRICANE GORDON DISCUSSION NUMBER 18 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072006 500 AM EDT FRI SEP 15 2006 SATELLITE IMAGERY SHOWS THAT GORDON HAS BEGUN TO WEAKEN...WITH AN EROSION OF THE COLD CLOUD TOPS OVER THE NORTHWEST QUADRANT OF THE CYCLONE AND THE EYE BECOMING SMALLER AND LESS DISTINCT. DVORAK DATA T-NUMBERS FROM SAB AND TAFB ARE 5.0...AND THE ADVISORY INTENSITY IS LOWERED TO 95 KT. GORDON SHOULD CONTINUE TO SLOWLY WEAKEN OVER THE NEXT COUPLE OF DAYS AS IT ENCOUNTERS PROGRESSIVELY COOLER SSTS. AFTER 2-3 DAYS...THE GFDL AND ALL OF THE GLOBAL MODELS...EXCEPT THE NOGAPS...SHOW GORDON BECOMING EXTRATROPICAL AS THE CYCLONE BECOMES EMBEDDED IN THE 1000-500 MB THICKNESS GRADIENT. ADDITIONALLY...THE GFS...ECMWF...CANADIAN AND UMKET MODELS SUGGEST THAT GORDON WILL REMAIN A ROBUST CYCLONE AFTER IT BECOMES EXTRATROPICAL...AND PERHAPS EVEN INTENSIFY...AS IT MOVES INTO THE FAVORABLE RIGHT-ENTRANCE REGION OF THE POLAR JET. THE INTENSITY FORECAST REFLECTS THIS...AND KEEPS THE INTENSITY AT 50 KT AFTER GORDON BECOMES EXTRATROPICAL. THE INITIAL MOTION ESTIMATE IS 060/08...TO THE RIGHT OF THE PREVIOUS FORECAST. IN SPITE OF THE MORE EASTERLY INITAL MOTION...MOST OF THE GLOBAL MODELS ARE TO THE LEFT OF THE PREVIOUS FORECAST FOR THE FIRST 24 HOURS...WITH THE GFS AND ITS ENSEMBLE MEAN ON THE LEFT SIDE OF THE GUIDANCE SUITE AND THE NOGAPS TO THE RIGHT. THE MORE POLEWARD MOTION IN THE GLOBAL MODELS IS DUE TO THE INTERACTION OF GORDON WITH A MID-LEVEL TROUGH OVER THE EASTERN UNITED STATES AND AN EXTRATROPICAL CYCLONE THAT MOVES EAST FROM THE CAROLINAS OVER THE WEEKEND. BY 72 HOURS...ALL THE GUIDANCE SHOWS AN ACCELERATION TO THE EAST-NORTHEAST AS GORDON BECOMES EXTRATROIPICAL. THE OFFICAL FORECAST IS A BLEND OF THE GLOBAL MODEL CONSENSUS AND THE PREVIOUS FORECAST...AND TRENDS TOWARD THE SPEED OF THE GLOBAL MODEL CONSENSUS THROUGH THE PERIOD. FORECAST POSITIONS AND MAX WINDS INITIAL 15/0900Z 30.9N 53.4W 95 KT 12HR VT 15/1800Z 31.4N 53.1W 90 KT 24HR VT 16/0600Z 32.1N 52.5W 80 KT 36HR VT 16/1800Z 33.0N 51.9W 70 KT 48HR VT 17/0600Z 34.7N 50.5W 60 KT 72HR VT 18/0600Z 38.5N 43.5W 50 KT...BECOMING EXTRATROPICAL 96HR VT 19/0600Z 42.0N 32.0W 50 KT...EXTRATROPICAL 120HR VT 20/0600Z 46.0N 19.0W 50 KT...EXTRATROPICAL $$ FORECASTER BRENNAN/KNABB |