538 
 WTNT43 KNHC 172031
 TCDAT3
 HURRICANE HELENE DISCUSSION NUMBER  22
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082006
 500 PM EDT SUN SEP 17 2006
  
 THERE HAS BEEN A DATA BONUS TODAY. A NOAA P-3 PLANE ON A RESEARCH
 MISSION HAS MADE TWO FIXES ON HELENE AND JUST REPORTED A MINIMUM
 PRESSURE OF 970 MB AND FLIGHT LEVEL WINDS OF 111 KNOTS AT 850 MB. A
 DROPSONDE MEASURED A SURFACE WIND OF 90 KNOTS BUT THIS MIGHT NOT
 REPRESENT A SUSTAINED VALUE. ALL OF THE ABOVE OBSERVATIONS
 COINCIDES WITH T-NUMBERS OF 5.0 ON THE DVORAK SCALE ESTIMATED BY
 ALL AGENCIES. I WAS TEMPTED TO LOWER THE INTENSITY A LITTLE BIT
 SINCE THE SFMR ON BOARD OF NOAA PLANE HAS ONLY REPORTED PEAK WINDS
 OF 80 KNOTS SO FAR.  HOWEVER...GIVEN THE CURRENT SATELLITE
 PRESENTATION...THE 3-H AVERAGE OBJECTIVE NUMBERS AODT= 5.6 FROM
 UW-CIMSS...AND THE DROP IN PRESSURE FROM THE 976 MB VALUE IN THE
 PREVIOUS FIX...THE INITIAL INTENSITY IS KEPT AT 90 KNOTS AT THIS
 TIME.  SOME ADDITIONAL STRENGTHENING IS POSSIBLE 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 NOW MOVING TOWARD THE NORTHWEST OR 315 DEGREES AT 8 KNOTS
 BETWEEN THE SUBTROPICAL RIDGE AND WEAKNESS LEFT BY HURRICANE
 GORDON. HOWEVER...AS GORDON MOVES OUT THE RIDGE IS EXPECTED TO
 BUILD WESTWARD AND THIS PATTERN COULD STEER HELENE TEMPORARILY ON A
 MORE WESTWARD TRACK UNTIL A LARGE TROUGH BECOMES IN PLACE OVER THE
 WESTERN ATLANTIC AND FORCES HELENE NORTHWARD. THE WESTWARD TURN FOR
 THE NEXT 2 TO 3 DAYS IS SHOWN BY EVERY MODEL. THERE IS HIGH
 UNCERTAINTY THEREAFTER SINCE GLOBAL MODELS HAVE BEEN SHIFTING THE
 TRACK FROM ONE RUN TO THE NEXT. THE GFS HAS HAD THE LEFTMOST TRACK
 SO FAR...BUT NOW THE UKMET MODEL HAS SHIFTED TO NEAR THE GFS
 SOLUTION. THE GFDL HAS BEEN VERY CONSISTENT IN TURNING HELENE
 NORTHWARD AND ITS SOLUTION IS HEAVILY WEIGHTED IN THE OFFICIAL
 FORECAST.  
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      17/2100Z 21.2N  49.3W    90 KT
  12HR VT     18/0600Z 22.0N  50.3W    95 KT
  24HR VT     18/1800Z 22.8N  51.5W   100 KT
  36HR VT     19/0600Z 23.1N  53.0W   100 KT
  48HR VT     19/1800Z 23.5N  55.0W    95 KT
  72HR VT     20/1800Z 24.5N  57.5W    90 KT
  96HR VT     21/1800Z 27.1N  59.5W    85 KT
 120HR VT     22/1800Z 30.5N  61.0W    80 KT
  
 $$
 
 FORECASTER AVILA