ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM 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 NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:43 UTC