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Hurricane HELENE (Text)


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HURRICANE HELENE DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
500 PM EDT MON SEP 18 2006
 
A NOAA RESEARCH AIRCRAFT MADE A PASS THROUGH THE CENTER OF HELENE
EARLIER TODAY AND FOUND THAT THE HURRICANE WAS NOT AS STRONG AS
PREVIOUSLY ESTIMATED BY SATELLITE. THEY MEASURED A MINIMUM PRESSURE
OF 966 MB AND SEVERAL MILLIBARS LOWER TWO HOURS LATER. MAXIMUM
WINDS REPORTED FROM THE SFMR INSTRUMENT ONBOARD THE PLANE WERE ONLY
79 KNOTS. HOWEVER...THE SATELLITE PRESENTATION STILL SUPPORTS WINDS
STRONGER THAN 100 KNOTS. AT THIS TIME...I AM ASSUMING THAT THE NOAA
PLANE DID NOT SAMPLE THE ENTIRE CIRCULATION AND THE INITIAL
INTENSITY IS ADJUSTED TO 100 KNOTS. IF THE SATELLITE PRESENTATION
DETERIORATES LATER TODAY OR TONIGHT...WINDS COULD BE ADJUSTED
DOWNWARD. HELENE COULD STRENGTHEN A LITTLE DURING THE NEXT DAY OR
SO SINCE THE SHEAR IS FORECAST TO BE LOW AND THE OCEAN IS WARM. 
MOST OF THE INTENSITY GUIDANCE SHOWS NO SIGNIFICANT CHANGE IN
STRENGTH DURING THE NEXT DAY OR TWO. 

HELENE IS NOW MOVING TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 8
KNOTS. THE SUBTROPICAL RIDGE NORTH OF HELENE IS FORECAST TO EXPAND
WESTWARD DURING THE NEXT DAY OR TWO. THIS PATTERN WOULD TEMPORARILY
STEER HELENE TOWARD THE WEST. HOWEVER...BEYOND TWO DAYS A LARGE
TROUGH IS FORECAST TO DEVELOP OVER THE WESTERN ATLANTIC...FORCING
HELENE TO TURN NORTHWARD AND NORTHEASTWARD WITH INCREASING FORWARD
SPEED. I AM MUCH MORE CONFIDENT IN THIS TRACK FORECAST SINCE ALL
THE GLOBAL MODELS ARE NOW IN GOOD AGREEMENT...AND THEIR SOLUTION
BECAME CLOSER TO THE GFDL...WHICH HAS BEEN STUBBORNLY TURNING HELENE
NORTHWARD ALL ALONG. DUE TO THE EASTWARD CHANGE IN THE GLOBAL
MODELS IN THE LATEST RUN...THE OFFICIAL FORECAST HAS BEEN SHIFTED A
LITTLE BIT EASTWARD AND IS NOW SHOWING RECURVATURE EAST OF 60W
LONGITUDE.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/2100Z 23.9N  51.1W   100 KT
 12HR VT     19/0600Z 24.6N  52.2W   100 KT
 24HR VT     19/1800Z 24.7N  54.0W   105 KT
 36HR VT     20/0600Z 24.8N  56.5W   105 KT
 48HR VT     20/1800Z 26.0N  57.0W   105 KT
 72HR VT     21/1800Z 29.5N  58.5W   100 KT
 96HR VT     22/1800Z 33.0N  57.5W    90 KT
120HR VT     23/1800Z 40.0N  50.0W    80 KT
 
$$
FORECASTER AVILA
 
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Page last modified: Monday, 18-Sep-2006 20:40:01 UTC