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Hurricane ILEANA


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HURRICANE ILEANA DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP102006
800 AM PDT WED AUG 23 2006

THERE HAS BEEN LITTLE CHANGE TO THE SATELLITE APPEARANCE OR THE
VARIOUS SATELLITE INTENSITY ESTIMATES DURING THE LAST 6 HOURS. 
ASSUMING THAT THE EARLIER INTENSIFICATION TREND IS CONTINUING...THE
INITIAL INTENSITY IS INCREASED SLIGHTLY TO 105 KT. HAVING SAID
THAT...THE LAST FEW INFRARED IMAGES SUGGEST AN EYEWALL REPLACEMENT
CYCLE COULD BE BEGINNING...WITH BREAKS IN THE INNER RING OF COLD
CLOUD TOPS AND HINTS OF AN OUTER RING DEVELOPING.  EYEWALL
REPLACEMENT CYCLES TEND TO ARREST DEVELOPMENT DURING THE SHORT-TERM
FOLLOWED BY SOME INTENSIFICATION.  WHILE FORECASTING SUCH INNER
CORE STRUCTURAL CHANGES IS DIFFICULT...ILEANA IS LOCATED WITHIN A
SEEMINGLY OPTIMAL ENVIRONMENT FOR STRENGTHENING. THEREFORE...THE
OFFICIAL FORECAST CONTINUES TO SHOW ILEANA BECOMING A CATEGORY 4
HURRICANE WITHIN THE NEXT 24 HOURS.  THEREAFTER...THE CYCLONE WILL
ENCOUNTER COOLER WATERS AND A MORE STABLE ATMOSPHERE.  THESE
FACTORS ARE EXPECTED TO CAUSE A RAPID DECREASE IN INTENSITY...
ESPECIALLY BEYOND 48 HOURS.  THE ONLY CHANGE TO THE PREVIOUS
INTENSITY FORECAST IS TO SHOW A QUICKER DEMISE ONCE ILEANA REACHES
COOLER WATERS. 
  
THE INITIAL MOTION ESTIMATE IS 300/11...A LITTLE SLOWER THAN BEFORE.
IT WOULD APPEAR THAT THE ANTICIPATED WEAKENING OF THE MID-LEVEL
ANTICYCLONE OVER NORTHERN MEXICO AND THE SOUTHWESTERN UNITED STATES
HAS COMMENCED.   ACCORDINGLY...THE FORWARD SPEED OF THE TROPICAL
CYCLONE IS PREDICTED TO DECREASE THROUGHOUT THE FORECAST PERIOD...
ESPECIALLY AT DAYS 3 THROUGH 5...AS THE GLOBAL MODELS FORECAST A
MID-LATITUDE TROUGH TO DIG SOUTHWARD OVER THE WESTERN UNITED
STATES.  THE GFS AND ITS ENSEMBLE MEAN...BOTH OF WHICH CONTINUE TO
SUFFER FROM POOR INITIALIZATION OF THE VORTEX STRENGTH AND
STRUCTURE...ARE FURTHER SOUTH SINCE THEY DO NOT RESPOND TO THE
AMPLIFYING TROUGH BUT THOSE SOLUTIONS APPEAR LESS LIKELY.  THE
OFFICIAL FORECAST IS CLOSE TO THE CONSENSUS OF THE REMAINING MODELS
AND REFLECTS ONLY MINOR ADJUSTMENTS TO THE PREVIOUS ADVISORY. 

A NEARBY STATION AT SOCORRO ISLAND OPERATED BY THE MEXICAN NAVY 
REPORTED SUSTAINED WINDS OF 38 KT WITH GUSTS TO 53 KT AT 1200 UTC.
THIS OBSERVATION WAS USEFUL IN ADJUSTING THE 34 KT WIND RADII
INWARD IN THE NORTHERN SEMICIRCLE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/1500Z 18.1N 111.5W   105 KT
 12HR VT     24/0000Z 19.0N 113.2W   110 KT
 24HR VT     24/1200Z 20.0N 115.2W   115 KT
 36HR VT     25/0000Z 20.8N 116.8W    95 KT
 48HR VT     25/1200Z 21.3N 118.0W    85 KT
 72HR VT     26/1200Z 22.0N 119.5W    60 KT
 96HR VT     27/1200Z 22.5N 121.0W    40 KT
120HR VT     28/1200Z 22.5N 122.0W    30 KT
 
$$
FORECASTER RHOME/KNABB
 
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