123 
 WTNT43 KNHC 161447
 TCDAT3
 HURRICANE HELENE DISCUSSION NUMBER  17
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
 1100 AM EDT SAT SEP 16 2006
  
 GEOSTATIONARY SATELLITE IMAGERY INDICATES INCREASING ORGANIZATION OF
 HELENE WITH ROBUST BANDING CONVECTION ON THE NORTH AND WEST
 QUADRANTS...AND A RAGGED EYE ATTEMPTING TO FORM AS SEEN IN THE
 VISIBLE IMAGERY.  MOREOVER...SSMI AND AMSU PASSES SHOW A NEARLY
 COMPLETE EYEWALL.  BASED UPON CONSENSUS OF DVORAK ESTIMATES...THE
 SYSTEM IS UPGRADED TO A 65 KT HURRICANE.  WHILE A SAHARAN AIR-LAYER
 IS SEEN TO THE NORTH AND WEST OF HELENE IN CIMSS IMAGERY...TOTAL
 PRECIPITABLE WATER ANALYSES FROM CIRA SUGGEST THAT THE DRY AIR
 REMAINS AT LEAST A COUPLE HUNDRED MILES FROM THE CENTER OF THE
 SYSTEM. CONTINUED SLOW INTENSIFICATION IS SUGGESTED OVER THE NEXT
 THREE DAYS DUE TO 27.5 C SSTS...LIGHT/MODERATE VERTICAL SHEAR...AND
 A MOIST ENVIRONMENT.  AT DAYS 4 AND 5...THE SSTS WARM UP...BUT
 SHEAR INCREASES MAY MITIGATE FURTHER INTENSIFICATION.  A PLATEAUING
 OF THE INTENSITY IS CALLED FOR AROUND 72 HRS WITH SLIGHT WEAKENING
 THEREAFTER.  THE INTENSITY FORECAST IS A BLEND OF THE SHIPS...FSU
 SUPER-ENSEMBLE...AND GFDL MODELS...WHICH IS SLIGHTLY WEAKER THAN
 PREVIOUSLY PREDICTED AT THE LONG-LEADS.
 
 CURRENT MOTION ESTIMATE IS 305/12.  HELENE IS ON THE SOUTHWEST SIDE
 OF A DEEP-LAYER RIDGE AND IS HEADED TOWARD A BREAK IN THE RIDGE...
 WHICH IS PARTIALLY BEING PRODUCED BY HURRICANE GORDON.  ALL
 RELIABLE GUIDANCE IS IN CLOSE AGREEMENT WITH A CONTINUED MOVEMENT
 ALONG THIS HEADING THROUGH 72 HR.  AT DAYS 4 AND 5...THERE IS A
 SIGNIFICANT MODEL DIVERGENCE WITH THE UK...GFDL...ECMWF BEING
 FASTER AND OFF TO THE NORTH AND THE GFS AND GFS ENSEMBLE SLOWER AND
 OFF TO THE SOUTH.  THESE DIFFERENCES ARE BEING DRIVEN BY THE
 AMPLITUDE OF THE SHORT-WAVE TROUGH THAT WILL BE PUSHING OFF OF THE
 US EAST COAST AT THAT TIME.  THE NOGAPS AND CONSENSUS MODELS ARE IN
 BETWEEN THESE POSSIBILITIES.  THE TRACK FORECAST IS CLOSE TO THE
 CONSENSUS MODELS AND SLIGHTLY SLOWER AND TO THE RIGHT OF THE
 PREVIOUS PREDICTION.
  
 A G-IV AIRCRAFT RESEARCH MISSION IS CURRENTLY ENROUTE TO SAMPLE
 HELENE'S ENVIRONMENT AS PART OF NOAA'S SALEX EXPERIMENT.
 
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      16/1500Z 18.8N  45.6W    65 KT
  12HR VT     17/0000Z 19.5N  46.9W    70 KT
  24HR VT     17/1200Z 20.4N  48.3W    75 KT
  36HR VT     18/0000Z 21.1N  49.4W    80 KT
  48HR VT     18/1200Z 21.9N  50.6W    85 KT
  72HR VT     19/1200Z 23.5N  53.5W    90 KT
  96HR VT     20/1200Z 25.5N  56.5W    85 KT
 120HR VT     21/1200Z 28.5N  58.0W    80 KT
  
 $$
 FORECASTER BEVEN/LANDSEA