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Hurricane HELENE (Text)

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HURRICANE HELENE DISCUSSION NUMBER  32
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
500 AM EDT WED SEP 20 2006
 
SATELLITE INTENSITY ESTIMATES ARE A CONSENSUS T5.5/102 KT.
HOWEVER...THE EYE FEATURE IN INFRARED SATELLITE IMAGERY HAS BECOME
RAGGED AND LESS DISTINCT...SO THE INITIAL INTENSITY WILL REMAIN AT
95 KT FOR THIS ADVISORY. UPPER-LEVEL OUTFLOW REMAINS EXCELLENT IN
ALL QUADRANTS...EXCEPT SLIGHTLY RESTRICTED TO THE SOUTHWEST.
 
THE INITIAL MOTION ESTIMATE IS NOW 305/08 KT. THE LONG ANTICIPATED
TURN TOWARD THE NORTHWEST THAT ALL OF THE GLOBAL AND REGIONAL
MODELS HAVE BEEN ADVERTISING FOR THE PAST FEW DAYS APPEARS TO
FINALLY BE UNDERWAY. A NARROW AND ELONGATED MID-LEVEL TROUGH
BETWEEN 65W-70W LONGITUDE IS EXPECTED TO SLOWLY TURN HELENE MORE
NORTHWARD DURING THE NEXT 36 HOURS...WITH A LARGER AND MORE
HIGHLY-AMPLIFIED TROUGH FORECAST TO MOVE EASTWARD OFF THE U.S. EAST
COAST AND ACCELERATING THE CYCLONE NORTHEASTWARD AFTER 48 HOURS.
THE OFFICIAL FORECAST TRACK IS SIMILAR TO BUT A LITTLE TO THE RIGHT
OF THE PREVIOUS TRACK AFTER 48 HOURS...AND IS CLOSE TO THE MIDDLE
OF THE TIGHTLY PACKED NHC MODEL GUIDANCE.
 
THE OUTFLOW PATTERN ON THE WEST SIDE HAS BECOME FLATTENED A LITTLE
BIT AS SOUTHWESTERLY UPPER-LEVEL FLOW AHEAD OF THE TROUGH ALONG
65W-70W LONGITUDE IS BEGINNING TO IMPINGE ON THE CYCLONE. THIS
SLIGHTLY UNFAVORABLE FLOW PATTERN SHOULD INHIBIT THE
INTENSIFICATION PROCESS...BUT THE SHEAR WILL STILL BE LOW ENOUGH
AND THE SSTS WARM ENOUGH TO ALLOW FOR SOME STRENGTHENING...AND
HELENE COULD BECOME A MAJOR HURRICANE AGAIN BEFORE IT BEGINS TO
RECURVE IN 36 HOURS. AFTER THAT...STEADILY INCREASING SOUTHWESTERLY
VERTICAL SHEAR COUPLED WITH DECREASING SSTS SHOULD INITIATE A SLOW
WEAKENING TREND. BY 72-96 HOURS...A TRANSITION OVER TO A POWERFUL
EXTRATROPICAL LOW PRESSURE IS EXPECTED AS THE LARGE TROUGH OVER THE
EASTERN U.S. MOVES EASTWARD AND EVENTUALLY CAPTURES HELENE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 25.3N  55.4W    95 KT
 12HR VT     20/1800Z 26.4N  56.3W   100 KT
 24HR VT     21/0600Z 28.6N  56.9W   100 KT
 36HR VT     21/1800Z 31.0N  56.7W    95 KT
 48HR VT     22/0600Z 33.9N  55.0W    90 KT
 72HR VT     23/0600Z 39.7N  48.0W    80 KT
 96HR VT     24/0600Z 45.0N  38.0W    70 KT...BECOMING EXTRATROPICAL
120HR VT     25/0600Z 49.0N  29.0W    60 KT...EXTRATROPICAL
 
$$
FORECASTER STEWART
 
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