684 
 WTNT43 KNHC 220239
 TCDAT3
 HURRICANE HELENE DISCUSSION NUMBER  39
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
 1100 PM EDT THU SEP 21 2006
 
 THE SATELLITE REPRESENTATION OF HELENE HAS IMPROVED SLIGHTLY DURING
 THE LAST COUPLE OF HOURS...AND COLD CLOUD TOPS HAVE EXPANDED AND
 BECOME MORE CONCENTRIC AROUND THE CENTER.  DVORAK DATA-T NUMBERS
 HAVE INCREASED TO 4.5 OR 77 KT FOR BOTH TAFB AND AFWA. 
 ACCORDINGLY...THE INITIAL INTENSITY HAS BEEN BUMPED UP TO 75 KT.   
 
 THE OFFICIAL INTENSITY FORECAST CLOSELY FOLLOWS THE SHIPS GUIDANCE. 
 HELENE IS EXPECTED TO REMAIN OVER 26C TO 27C WATER FOR THE NEXT 24
 HOURS OR SO WITH ONLY A MARGINAL INCREASE IN WEST-SOUTHWESTERLY
 SHEAR.  THIS SHOULD KEEP HELENE IN A STEADY STATE FOR THE NEXT DAY. 
 AFTER WHICH...VERY SLOW WEAKENING IS ANTICIPATED AS HELENE
 TRANSITIONS INTO A POTENTIALLY STRONG EXTRATROPICAL CYCLONE IN
 ABOUT 2 TO 3 DAYS...AS COLD AIR BECOMES ENTRAINED INTO THE WESTERN
 SIDE OF THE CYCLONE.  
 
 THE INITIAL MOTION IS NORTH-NORTHEASTWARD OR 015/12.  WATER VAPOR
 IMAGERY INDICATES A BROAD DEEP-LAYER TROUGH RACING EASTWARD TOWARD
 HELENE WITH A DRY PUNCH OUT AHEAD OF IT.  THIS TROUGH WILL HELP
 ACCELERATE HELENE TO THE NORTH-NORTHEAST AND NORTHEAST FOR THE NEXT
 48 TO 72 HOURS.  THE MODEL GUIDANCE IS CONSISTENT WITH THIS
 SCENARIO...THEN THE MODELS DIVERGE A BIT AT DAYS 4 AND 5 AS HELENE
 BECOMES EXTRATROPICAL.  THE UKMET IS THE GREATEST OUTLIER AND TAKES
 HELENE TO THE EAST AND EVENTUALLY TO THE SOUTH...AND SHIFTS THE
 CONSENSUS GUIDANCE TO THE SOUTH AS WELL.  THE GFS HAS A MORE
 NORTHWARD TRACK WHILE THE GFDL...NOGAPS...AND FSU SUPERENSEMBLE
 TAKE THE CYCLONE TO THE NORTHEAST.  THE OFFICIAL FORECAST IS
 SLIGHTLY SOUTH OF THE PREVIOUS TRACK BUT REMAINS IN CLOSE AGREEMENT
 WITH GFDL AND FSU SUPERENSEMBLE SOLUTIONS. 
 
 THE WIND RADII HAVE BEEN ADJUSTED TO REFLECT DATA FROM A 2226 UTC
 QUIKSCAT PASS. 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      22/0300Z 31.8N  56.3W    75 KT
  12HR VT     22/1200Z 33.6N  54.8W    75 KT
  24HR VT     23/0000Z 36.3N  51.2W    75 KT
  36HR VT     23/1200Z 38.9N  45.9W    70 KT
  48HR VT     24/0000Z 41.7N  40.0W    65 KT...BECOMING EXTRATROPICAL
  72HR VT     25/0000Z 47.0N  30.0W    60 KT...EXTRATROPICAL
  96HR VT     26/0000Z 51.5N  23.0W    60 KT...EXTRATROPICAL
 120HR VT     27/0000Z 58.0N  17.0W    55 KT...EXTRATROPICAL
  
 $$
 FORECASTER MAINELLI/BEVEN