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Hurricane HELENE (Text)

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HURRICANE HELENE DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
1100 AM EDT MON SEP 18 2006
 
HELENE AND GORDON WERE BASICALLY AT THE SAME LONGITUDE THIS MORNING
AND THERE WAS A WEAKENING ON THE RIDGE NORTH OF HELENE. THIS
RESULTED IN HELENE MOVING IN A NORTH-NORTHWESTWARD TRACK FOR THE
PAST SEVERAL HOURS.  HOWEVER...IT APPEARS THAT THE HURRICANE IS
READY TO BEGIN THE WESTWARD TURN ANTICIPATED BY THE GLOBAL MODELS.
IN FACT...HELENE HAS ALREADY TURNED A LITTLE BIT AND IS NOW MOVING
TOWARD THE NORTHWEST OR 310 DEGREES AT 8 KNOTS. THE TROUGH
CURRENTLY LOCATED OVER THE WESTERN ATLANTIC IS FORECAST TO WEAKEN
WHILE A RIDGE TO THE NORTH OF HELENE IS EXPECTED TO AMPLIFY. THIS
PATTERN WOULD TEMPORARILY STEER HELENE ON A WESTWARD TRACK FOR A
COUPLE OF DAYS.  THEREAFTER...GLOBAL MODELS SHOW ANOTHER LARGE
TROUGH APPROACHING THE EASTERN UNITED STATES. THIS TROUGH WILL
FORCE HELENE SLOWLY NORTHWARD. ALTHOUGH...THE CONFIDENCE IS QUITE
HIGH THAT HELENE WILL EVENTUALLY TURN NORTHWARD...IT IS VERY
DIFFICULT TO FORECAST THE LONGITUDE THIS WILL OCCUR. THERE ARE SOME
INDICATIONS FROM THE LAST RUN OF THE GLOBAL MODELS THAT BY DAYS 4
AND 5...THE STEERING CURRENTS WILL WEAKEN AND HELENE WILL BE MOVING
VERY SLOWLY.        

THERE HAS NO SIGNIFICANT CHANGE IN THE CLOUD PATTERN...JUST A SMALL
INCREASE IN THE DVORAK T-NUMBERS. THEREFORE...THE INTENSITY HAS
BEEN ADJUSTED UPWARD TO 110 KNOTS.  A NOAA P3 PLANE AND NOAA G4
JET...CURRENTLY ON A RESEARCH MISSION IN THE AREA WILL BE PROVIDING
VALUABLE DATA THIS AFTERNOON AND WE COULD HAVE A BETTER ESTIMATE OF
THE STRUCTURE OF THE HURRICANE AND THE STEERING.  HELENE COULD
STRENGTHEN JUST LITTLE BIT MORE SINCE THE SHEAR IS LOW AND THE
OCEAN IS WARM.  HOWEVER...MOST OF THE INTENSITY GUIDANCE FORECAST
LITTLE CHANGE OR GRADUAL WEAKENING.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/1500Z 23.2N  50.2W   110 KT
 12HR VT     19/0000Z 23.9N  51.0W   110 KT
 24HR VT     19/1200Z 24.3N  52.8W   115 KT
 36HR VT     20/0000Z 24.3N  54.5W   115 KT
 48HR VT     20/1200Z 24.5N  56.0W   110 KT
 72HR VT     21/1200Z 27.0N  58.0W   105 KT
 96HR VT     22/1200Z 29.5N  59.5W   100 KT
120HR VT     23/1200Z 31.5N  60.5W    95 KT
 
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FORECASTER AVILA
 
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