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| #146873 (Received by flhurricane at: 11:08 PM 18.Aug.2007) TCDAT4 HURRICANE DEAN DISCUSSION NUMBER 24 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007 1100 PM EDT SAT AUG 18 2007 THE INNER CORE OF DEAN APPEARS TO BE UNDERGOING SOME CHANGES. RADAR IMAGERY ONBOARD THE AIR FORCE RECONNAISSANCE AIRCRAFT DEPICTS CONCENTRIC EYEWALLS AT RADII OF ABOUT 10 AND 20 N MI...WITH THE OUTER EYEWALL RECENTLY BECOMING A LITTLE BETTER DEFINED. FLIGHT-LEVEL WINDS HAVE ALSO REVEALED DOUBLE MAXIMA. WIND DATA AT FLIGHT LEVEL...FROM THE SFMR...AND FROM DROPSONDES DIRECTLY SUPPORT AN INTENSITY OF NO MORE THAN ABOUT 115 KT. THE CENTRAL PRESSURE...HOWEVER...HAS BEEN GRADUALLY DROPPING AND WAS MOST RECENTLY MEASURED AT 918 MB. ASSUMING THAT THE MAXIMUM WIND HAS NOT BEEN SAMPLED...THE ADVISORY INTENSITY IS SET TO 125 KT...BUT THIS COULD BE A BIT ON THE HIGH SIDE. THE AIRCRAFT WILL CONTINUE TO INVESTIGATE DEAN FOR A FEW MORE HOURS TO SEE IF THE WINDS COME BACK UP. DEAN WOBBLED WESTWARD EARLIER THIS EVENING...BUT THE LONGER-TERM MOTION TOWARD 280 DEGREES AT ABOUT 15 KT SEEMS TO HAVE RESUMED. AS THE MODELS HAVE BEEN FORECASTING...THE MID- TO UPPER-LEVEL LOW THAT WAS EAST OF FLORIDA A COUPLE OF DAYS AGO IS NOW OVER THE EASTERN GULF OF MEXICO AND HEADED QUICKLY WESTWARD. THAT LOW IS FORECAST TO BE REPLACED BY A LARGE AND STRONG RIDGE OVER THE SOUTHEASTERN UNITED STATES DURING THE NEXT COUPLE OF DAYS...WHICH SHOULD REINFORCE A GENERAL WEST-NORTHWESTWARD MOTION OF DEAN...THROUGH THE NORTHWESTERN CARIBBEAN...OVER SOME PORTION OF THE YUCATAN PENINSULA...AND INTO THE SOUTHERN GULF OF MEXICO. THE MODELS HAVE IN GENERAL SHIFTED SLIGHTLY SOUTHWARD...INCLUDING THE GFDL WHICH IS NO LONGER THE NORTHERN OUTLIER. THE GUIDANCE IS NOW IN VERY GOOD AGREEMENT ON THE TRACK THROUGHOUT THE ENTIRE FIVE-DAY FORECAST PERIOD...SO CONFIDENCE IN THE TRACK FORECAST IS INCREASING. THE OFFICIAL TRACK FORECAST HAS BEEN ADJUSTED A TAD TO THE SOUTH AND IS VERY NEAR THE DYNAMICAL MODEL CONSENSUS. THE SHORT-TERM INTENSITY FORECAST IS A BIT UNCERTAIN GIVEN THE DOUBLE EYEWALL STRUCTURE...BUT THE CENTRAL PRESSURE IS QUITE LOW AND THE INNER CORE COULD QUICKLY REORGANIZE AT ANY TIME...SO ANY DIP IN THE INTENSITY WILL PROBABLY BE SHORT-LIVED. THROUGHOUT ITS STAY IN THE CARIBBEAN SEA DURING THE NEXT 48 HOURS OR SO...ATMOSPHERIC AND OCEANIC CONDITIONS REMAIN SUPPORTIVE OF A CATEGORY FOUR OR FIVE INTENSITY AS SUGGESTED BY ALL OF THE OBJECTIVE GUIDANCE. SINCE THE NEW TRACK FORECAST RESULTS IN A LONGER STAY OVER THE YUCATAN PENINSULA...THE OFFICIAL INTENSITY FORECAST HAS BEEN LOWERED SLIGHTLY OVER THE SOUTHWESTERN GULF OF MEXICO...BUT STILL INDICATES A MAJOR HURRICANE AT FINAL LANDFALL. FORECAST POSITIONS AND MAX WINDS INITIAL 19/0300Z 16.2N 71.7W 125 KT 12HR VT 19/1200Z 16.8N 74.3W 130 KT 24HR VT 20/0000Z 17.6N 77.8W 130 KT 36HR VT 20/1200Z 18.4N 81.4W 135 KT 48HR VT 21/0000Z 19.3N 85.1W 140 KT 72HR VT 22/0000Z 21.0N 92.0W 85 KT 96HR VT 23/0000Z 23.0N 98.0W 100 KT...INLAND 120HR VT 24/0000Z 24.0N 101.0W 30 KT...INLAND $$ FORECASTER KNABB |
