810 
 WTNT43 KNHC 182035
 TCDAT3
 HURRICANE HELENE DISCUSSION NUMBER  26
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
 500 PM EDT MON SEP 18 2006
  
 A NOAA RESEARCH AIRCRAFT MADE A PASS THROUGH THE CENTER OF HELENE
 EARLIER TODAY AND FOUND THAT THE HURRICANE WAS NOT AS STRONG AS
 PREVIOUSLY ESTIMATED BY SATELLITE. THEY MEASURED A MINIMUM PRESSURE
 OF 966 MB AND SEVERAL MILLIBARS LOWER TWO HOURS LATER. MAXIMUM
 WINDS REPORTED FROM THE SFMR INSTRUMENT ONBOARD THE PLANE WERE ONLY
 79 KNOTS. HOWEVER...THE SATELLITE PRESENTATION STILL SUPPORTS WINDS
 STRONGER THAN 100 KNOTS. AT THIS TIME...I AM ASSUMING THAT THE NOAA
 PLANE DID NOT SAMPLE THE ENTIRE CIRCULATION AND THE INITIAL
 INTENSITY IS ADJUSTED TO 100 KNOTS. IF THE SATELLITE PRESENTATION
 DETERIORATES LATER TODAY OR TONIGHT...WINDS COULD BE ADJUSTED
 DOWNWARD. HELENE COULD STRENGTHEN A LITTLE DURING THE NEXT DAY OR
 SO SINCE THE SHEAR IS FORECAST TO BE LOW AND THE OCEAN IS WARM. 
 MOST OF THE INTENSITY GUIDANCE SHOWS NO SIGNIFICANT CHANGE IN
 STRENGTH DURING THE NEXT DAY OR TWO. 
 
 HELENE IS NOW MOVING TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 8
 KNOTS. THE SUBTROPICAL RIDGE NORTH OF HELENE IS FORECAST TO EXPAND
 WESTWARD DURING THE NEXT DAY OR TWO. THIS PATTERN WOULD TEMPORARILY
 STEER HELENE TOWARD THE WEST. HOWEVER...BEYOND TWO DAYS A LARGE
 TROUGH IS FORECAST TO DEVELOP OVER THE WESTERN ATLANTIC...FORCING
 HELENE TO TURN NORTHWARD AND NORTHEASTWARD WITH INCREASING FORWARD
 SPEED. I AM MUCH MORE CONFIDENT IN THIS TRACK FORECAST SINCE ALL
 THE GLOBAL MODELS ARE NOW IN GOOD AGREEMENT...AND THEIR SOLUTION
 BECAME CLOSER TO THE GFDL...WHICH HAS BEEN STUBBORNLY TURNING HELENE
 NORTHWARD ALL ALONG. DUE TO THE EASTWARD CHANGE IN THE GLOBAL
 MODELS IN THE LATEST RUN...THE OFFICIAL FORECAST HAS BEEN SHIFTED A
 LITTLE BIT EASTWARD AND IS NOW SHOWING RECURVATURE EAST OF 60W
 LONGITUDE.
   
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      18/2100Z 23.9N  51.1W   100 KT
  12HR VT     19/0600Z 24.6N  52.2W   100 KT
  24HR VT     19/1800Z 24.7N  54.0W   105 KT
  36HR VT     20/0600Z 24.8N  56.5W   105 KT
  48HR VT     20/1800Z 26.0N  57.0W   105 KT
  72HR VT     21/1800Z 29.5N  58.5W   100 KT
  96HR VT     22/1800Z 33.0N  57.5W    90 KT
 120HR VT     23/1800Z 40.0N  50.0W    80 KT
  
 $$
 FORECASTER AVILA