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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