190 
 WTNT43 KNHC 171436
 TCDAT3
 HURRICANE HELENE DISCUSSION NUMBER  21
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
 1100 AM EDT SUN SEP 17 2006
  
 VISIBLE SATELLITE IMAGES SHOW THAT HELENE HAS DEVELOPED A LARGE
 RAGGED EYE SURROUNDED BY A RING OF DEEP CONVECTION. SATELLITE
 INTENSITY ESTIMATES FROM ALL AGENCIES HAVE INCREASED TO 5.0 ON THE
 DVORAK SCALE. THE 3-HOUR AVERAGE ADVANCED OBJECTIVE TECHNIQUE FROM
 THE UNIVERSITY OF WISCONSIN IS 5.6. ON THIS BASIS...THE INITIAL
 INTENSITY HAS BEEN INCREASED TO 90 KNOTS. THERE IS A CHANCE FOR AN 
 ADDITIONAL STRENGTHENING DURING THE NEXT DAY OR TWO BEFORE THE
 SHEAR INCREASES AS SUGGESTED BY SHIPS MODEL. THE OCEAN IS EXPECTED
 TO REMAIN WARM ALONG THE FORECAST TRACK.
 
 HELENE IS MOVING TOWARD THE NORTHWEST OR 305 DEGREES AT 9 KNOTS. THE
 FORECAST SCENARIO COULD BE DESCRIBED AS SUCH...HELENE CURRENTLY
 LOCATED ON THE SOUTHWESTERN EDGE A SUBTROPICAL RIDGE AND MOVING
 TOWARD A WEAKNESS CAUSED BY A SHARP MID-LEVEL SHORT WAVE JUST EAST
 OF THE UNITED STATES CAST. THEN...AS THE SHORT WAVE MOVES OUT THE
 AREA...THE RIDGE WILL LIKELY BUILD WESTWARD FORCING HELENE TO
 TEMPORARILY TURN MORE TO THE WEST-NORTHWEST. AFTER 3 DAYS...A
 LARGER TROUGH IS EXPECTED TO MOVE EASTWARD AND FINALLY PICK UP
 HELENE. THE DILEMMA IS HOW FAR WEST WILL HELENE GO SINCE TWO GOOD
 MODELS DIVERGE...PUTTING ME BETWEEN A ROCK AND HARD PLACE. THE GOOD
 GFS AND THE GFS ENSEMBLE MEAN HAVE THE WESTERNMOST SOLUTIONS WHILE
 THE OUTSTANDING AND HARD TO BEAT GFDL HAS HELENE TURNING NORTHWARD
 FARTHER EAST. SINCE THE REST OF THE GUIDANCE IS IN BETWEEN THESE
 TWO EXTREME OPTIONS...THE OFFICIAL FORECAST DOES IT AS WELL.  
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      17/1500Z 20.5N  49.0W    90 KT
  12HR VT     18/0000Z 21.3N  50.1W    95 KT
  24HR VT     18/1200Z 22.5N  51.5W   100 KT
  36HR VT     19/0000Z 23.0N  53.0W   100 KT
  48HR VT     19/1200Z 23.5N  54.5W    95 KT
  72HR VT     20/1200Z 24.5N  57.0W    90 KT
  96HR VT     21/1200Z 27.0N  59.0W    85 KT
 120HR VT     22/1200Z 30.0N  59.5W    80 KT
  
 $$
 FORECASTER AVILA