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 228 
 WTNT43 KNHC 142045
 TCDAT3
 TROPICAL STORM HELENE DISCUSSION NUMBER  10
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
 500 PM EDT THU SEP 14 2006
  
 THE OVERALL CLOUD PATTERN ASSOCIATED WITH HELENE HAS NOT CHANGED
 MUCH SINCE THIS MORNING...AND THERE ARE NO DISTINCT CONVECTIVE
 BANDING FEATURES.  HOWEVER...THERE IS A SMALL BURST OF CONVECTION
 THAT HAS RECENTLY DEVELOPED NEAR THE CENTER.  SATELLITE INTENSITY
 ESTIMATES REMAIN UNCHANGED FROM THIS MORNING AND THE INITIAL
 INTENSITY WILL REMAIN 40 KT.  A RATHER DISTINCT LOW-LEVEL
 CIRCULATION BECAME APPARENT IN VISIBLE IMAGERY LATE THIS MORNING
 WHICH WAS A LITTLE TO THE RIGHT OF THE PREVIOUS TRACK...AND THIS
 REQUIRED A SLIGHT ADJUSTMENT BOTH TO THE WORKING TRACK AND TO THE
 SHORT TERM FORECAST.
 
 HELENE HAS SLOWED DOWN DURING THE PAST 6 HOURS...BUT USING A LONGER
 TERM 12 HOUR AVERAGE YIELDS AN INITIAL MOTION ESTIMATE OF 285/14.
 HELENE IS MOVING WEST-NORTHWESTWARD SOUTH OF A MID-TO UPPER-LEVEL
 RIDGE.  THE GLOBAL MODELS IN GENERAL DEVELOP A BREAK IN THE RIDGE
 IN A COUPLE DAYS BETWEEN 50W AND 60W...WHICH SHOULD IMPART A MORE
 NORTHWESTWARD MOTION.  HOWEVER...THERE REMAINS A FAIRLY LARGE
 SPREAD IN THE MODELS AS TO WHEN THIS MAY OCCUR.  THE GFS...ITS
 ENSEMBLE MEAN...AND THE GFDL ARE TO THE RIGHT AND FORECAST THE
 RIDGE TO WEAKEN MUCH SOONER.  THE UKMET KEEPS THE RIDGE INTACT
 LONGER AND THEREFORE IS ON THE LEFT SIDE OF THE GUIDANCE.  THE
 OFFICIAL TRACK IS CLOSE TO THE FSU SUPERENSEMBLE AND GUNA 
 MODEL CONSENSUS.
 
 EVEN THOUGH THE OUTFLOW IS WELL ESTABLISHED AND HELENE IS IN A VERY
 LOW SHEAR ENVIRONMENT...THE LARGE CIRCULATION STILL LACKS INNER
 CORE CONVECTION.  UNTIL THE INNER CORE DEVELOPS...STRENGTHENING IS
 EXPECTED TO BE SLOW.  THE NHC INTENSITY FORECAST SHOWS AN INCREASE
 IN WIND SPEED MUCH LIKE THE SHIPS MODEL.  LATE IN THE PERIOD GLOBAL
 MODELS SUGGEST SOME INCREASING SHEAR WHICH COULD SLOW THE
 INTENSIFICATION.  ACCORDINGLY...THE OFFICIAL FORECAST IS NOT AS
 AGGRESSIVE AS THE FSU SUPERENSEMBLE AT DAYS 4 AND 5.
  
 THE WIND RADII WERE ADJUSTED OUTWARD BASED ON A RECENT REPORT OF 
 34 KT WINDS FROM A MOORED BUOY ABOUT 90 NM NORTHWEST OF HELENE.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      14/2100Z 14.2N  37.6W    40 KT
  12HR VT     15/0600Z 14.8N  39.7W    45 KT
  24HR VT     15/1800Z 16.0N  42.1W    55 KT
  36HR VT     16/0600Z 17.3N  44.4W    65 KT
  48HR VT     16/1800Z 18.5N  46.2W    75 KT
  72HR VT     17/1800Z 20.5N  49.0W    85 KT
  96HR VT     18/1800Z 22.5N  51.0W    90 KT
 120HR VT     19/1800Z 25.5N  54.0W    90 KT
  
 $$
 FORECASTER BROWN
  
 
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