Hurricane HELENE

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HURRICANE HELENE DISCUSSION NUMBER  49
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
500 AM EDT SUN SEP 24 2006
 
HELENE CONTINUES TO MAINTAIN DEEP CONVECTION NEAR THE
CENTER...ALTHOUGH THERE IS LESS OF IT NOW THAN 6 HOURS
AGO.  THE INITIAL INTENSITY WILL REMAIN 75 KT BASED ON THE EARIER
QUIKSCAT DATA.  OVER THE NEXT 24 HOURS...HELENE WILL BE MOVING OVER
COOLER WATERS AND THE VERTICAL SHEAR IS EXPECTED TO INCREASE. 
HOWEVER...INTERACTION WITH A SHORT-WAVE TROUGH IN THE WESTERLIES
APPROACHING HELENE COULD KEEP THE WINDS UP...SO LITTLE CHANGE IN
INTENSITY IS SHOWN UNTIL AFTER 24 HOURS...WHEN THE BAROCLINIC
FORCING IS EXPECTED TO DIMINISH.  HELENE IS EXPECTED TO LOSE
TROPICAL CHARACTERISTICS AS IT IS OVERTAKEN BY THE SHORT-WAVE
TROUGH IN ANOTHER 12 TO 24 HOURS...IF IT HASN'T ALREADY LOST IT'S
DEEP CONVECTION BY THEN.

MODEL GUIDANCE IS IN VERY GOOD AGREEMENT NOW ON A CONTINUED
EAST-NORTHEASTWARD MOTION...WITH ONLY THE ECMWF DROPPING HELENE
SOUTHWARD NEAR THE AZORES.  MUCH OF THE GUIDANCE SUGGESTS A SLOWING
OF THE TRACK IN ABOUT 24 HOURS AS MID-LATITUDE SHORT WAVE ENERGY
DROPS SOUTH OF HELENE...WEAKENING THE STEERING CURRENT.  THE
OFFICIAL FORECAST IS CLOSE TO THE PREVIOUS ADVISORY AND TO A
TIGHTLY-CLUSTERED GFS/GFDL/UKMET/NOGAPS CONSENSUS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      24/0900Z 39.9N  39.9W    75 KT
 12HR VT     24/1800Z 41.6N  36.6W    70 KT...EXTRATROPICAL
 24HR VT     25/0600Z 43.2N  33.1W    65 KT...EXTRATROPICAL
 36HR VT     25/1800Z 44.5N  30.0W    60 KT...EXTRATROPICAL
 48HR VT     26/0600Z 45.0N  26.0W    50 KT...EXTRATROPICAL
 72HR VT     27/0600Z 47.0N  18.0W    45 KT...EXTRATROPICAL
 96HR VT     28/0600Z...ABSORBED
 
$$
FORECASTER FRANKLIN
 
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