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| #214096 (Received by flhurricane at: 5:08 AM 06.Sep.2008) TCDAT4 HURRICANE IKE DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092008 500 AM EDT SAT SEP 06 2008 AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT RECORDED A MAXIMUM FLIGHT LEVEL WIND OF 104 KT OVER THE NORTHWEST QUADRANT AND AN SFMR PEAK WIND OF 96 KT OVER THE NORTHEASTERN PORTION OF THE CYCLONE. BASED ON THESE DATA...THE INITIAL INTENSITY IS HELD AT 100 KT. THE AIRCRAFT METEOROLOGIST ALSO INDICATED THAT IKE HAS A CLOSED 24 NM DIAMETER EYE. A DROPSONDE WITHIN THE EYE MEASURED 983 MB BUT THAT WAS WITH A SURFACE WIND OF 16 KT. AS A COMPROMISE...THE CENTRAL PRESSURE IS ADJUSTED SLIGHTLY TO 982 MB. ALTHOUGH NORTHERLY SHEAR SEEMS TO BE PERSISTING OVER THE CYCLONE...IT DOES NOT APPEAR TO BE AFFECTING THE INNER CORE CONVECTION AS MUCH AS IT WAS PREVIOUSLY. INTENSITY MODELS CONTINUE TO INDICATE THAT THE SHEAR WILL DECREASE IN ABOUT 24 HOURS...WHICH SHOULD ALLOW FOR SOME STRENGTHENING BEFORE IKE MOVES NEAR OR OVER THE NORTHERN COAST OF CUBA. THE INTENSITY FORECAST IS VERY SIMILAR TO THE PREVIOUS PACKAGE BUT NOW DEPICTS SOME WEAKENING AS IKE TRAVERSES THE CUBAN COAST. OF COURSE...ANY SLIGHT DEVIATION NORTH OR SOUTH OF THE FORECAST WILL EITHER ALLOW FOR STRENGTHENING OVER WATER OR A LONGER PERIOD OF WEAKENING OVER LAND. LATER ON...CONDITIONS APPEAR RATHER CONDUCIVE FOR STRENGTHENING OVER THE GULF OF MEXICO. INITIAL MOTION IS ESTIMATED AT 255/14...WITHIN THE DEEP-LAYER FLOW OF A STRONG RIDGE DIGGING SOUTHWESTWARD OVER THE BAHAMAS...THROUGH THE STRAITS OF FLORIDA...AND INTO THE SOUTHEASTERN GULF OF MEXICO. DYNAMICAL MODELS SUGGEST THAT THE RIDGE WILL SHIFT TO A MORE ZONAL PATTERN DURING THE NEXT 24 TO 36 HOURS WHICH WILL CAUSE IKE TO MOVE IN A MORE WESTWARD FASHION. AFTERWARD...GUIDANCE INDICATES THAT THE SOUTHWEST RIDGE EXTENSION OVER THE SOUTHEASTERN GULF/STRAITS OF FLORIDA WILL ERODE JUST ENOUGH TO INDUCE A GRADUAL TURN TOWARD THE NORTHWEST BY THE END OF THE FORECAST PERIOD. THERE IS MUCH UNCERTAINTY IN THE MODELS AS TO HOW CLOSE IKE WILL APPROACH THE NORTHERN COAST OF CUBA. IN FACT...THE TWO HURRICANE MODELS ACTUALLY BRING THE CYCLONE OVER THE ISLAND IN 36 HOURS. WITHOUT QUESTION...THE PARTICULAR TRACK THAT THE GFDL AND HWRF ARE SUGGESTING COULD HAVE A SIGNIFICANT IMPACT ON IKE'S INTENSITY. THE OFFICIAL FORECAST IS WEIGHED HEAVILY ON THE MODEL CONSENSUS AND IS ADJUSTED JUST TO THE LEFT OF THE PREVIOUS ADVISORY TO COMPENSATE FOR THE WESTWARD-SHIFTING MODEL TREND. FORECAST POSITIONS AND MAX WINDS INITIAL 06/0900Z 22.4N 67.1W 100 KT 12HR VT 06/1800Z 22.1N 69.0W 100 KT 24HR VT 07/0600Z 21.8N 71.6W 100 KT 36HR VT 07/1800Z 21.6N 74.1W 105 KT 48HR VT 08/0600Z 21.8N 76.6W 115 KT 72HR VT 09/0600Z 23.0N 80.5W 90 KT...NEAR COAST OF CUBA 96HR VT 10/0600Z 24.5N 83.5W 105 KT 120HR VT 11/0600Z 26.0N 85.5W 110 KT $$ FORECASTER ROBERTS/KNABB |
