Hurricane GORDON

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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
 
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