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Hurricane HERNAN (Text)

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HURRICANE HERNAN DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092008
800 AM PDT SUN AUG 10 2008

HERNAN CONTINUES ITS SLOW WEAKENING TREND AS IT MOVES OVER MODESTLY
COOLER WATERS.  ENHANCED INFRARED IMAGERY SHOWS AN EROSION OF THE
WESTERN PORTION OF THE EYEWALL.  DVORAK CURRENT INTENSITY ESTIMATES
AVERAGE ABOUT 80 KT...WHICH IS USED FOR THE ADVISORY WIND SPEED. 
DYNAMICAL MODEL PREDICTIONS INDICATE THAT VERTICAL SHEAR WILL
REMAIN VERY WEAK OVER HERNAN OVER THE NEXT FEW DAYS SO THE MAIN
CONTRIBUTION TO WEAKENING SHOULD COME FROM THERMODYNAMIC FACTORS. 
NEAR THE END OF THE FORECAST PERIOD...SEA SURFACE TEMPERATURES MAY
ACTUALLY BECOME A LITTLE WARMER.  BY THAT TIME...HOWEVER...THE
TROPICAL CYCLONE WILL PROBABLY HAVE WEAKENED CONSIDERABLY.  THE NHC
INTENSITY FORECAST IS SIMILAR TO THE SHIPS PREDICTION.   

INITIAL MOTION IS ABOUT 300/8.  THE HURRICANE HAD BEEN TRACKING
NORTHWESTWARD TOWARD A WEAKNESS IN THE SUBTROPICAL RIDGE BUT NOW
APPEARS TO HAVE TURNED TOWARD THE WEST-NORTHWEST.  GLOBAL MODELS
INDICATE THAT A MID-LEVEL RIDGE WILL BUILD TO THE NORTHWEST OF
HERNAN DURING THE NEXT SEVERAL DAYS...WHICH WOULD LIKELY FORCE A
CONTINUED TURN TOWARD THE LEFT.  THIS IS ALSO INDICATED BY THE
DYNAMICAL TRACK MODELS WHICH ARE IN FAIRLY GOOD AGREEMENT ABOUT A
TURN TOWARD THE WEST AND WEST-SOUTHWEST IN 48 HOURS.  THE OFFICIAL
TRACK FORECAST IS SOMEWHAT FASTER THAN THE PREVIOUS ONE AND QUITE
CLOSE TO THE MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 17.7N 126.6W    80 KT
 12HR VT     11/0000Z 18.2N 127.6W    70 KT
 24HR VT     11/1200Z 18.5N 129.1W    60 KT
 36HR VT     12/0000Z 18.4N 130.4W    50 KT
 48HR VT     12/1200Z 18.0N 131.7W    45 KT
 72HR VT     13/1200Z 17.2N 134.0W    40 KT
 96HR VT     14/1200Z 16.5N 136.5W    35 KT
120HR VT     15/1200Z 16.0N 140.0W    30 KT
 
$$
FORECASTER PASCH
 
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