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| #146478 (Received by flhurricane at: 11:17 PM 16.Aug.2007) TCDAT4 HURRICANE DEAN DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007 1100 PM EDT THU AUG 16 2007 THE SATELLITE PRESENTATION OF DEAN HAS DETERIORATED A BIT OVER THE LAST 12 HOURS...WITH NO EVIDENCE OF AN EYE IN CONVENTIONAL OR MICROWAVE IMAGERY. THE SFMR INSTRUMENT ON THE EARLIER AIR FORCE FLIGHT RECORDED A PEAK SURFACE WIND OF 88 KT AROUND 19Z IN THE SOUTHEAST PORTION OF THE EYEWALL...ALONG WITH VERY LITTLE WIND IN THE SOUTHWEST QUADRANT OF THE CIRCULATION. BASED ON THE EARLIER AIRCRAFT DATA AND RECENT STRUCTURAL TRENDS...THE INITIAL INTENSITY IS HELD AT 85 KT. COMMUNICATIONS DIFFICULTIES DURING THE RECONNAISSANCE MISSION PREVENTED MUCH OF THE DATA FROM GETTING TO US...BUT DROPSONDE DATA CALLED IN AFTERWARD BY THE CREW INDICATE THE CENTRAL PRESSURE IS A LITTLE LOWER THAN PREVIOUSLY ESTIMATED... ABOUT 976 MB. THE INITIAL MOTION IS 275/22. DEAN IS SOUTH OF A MID-LEVEL RIDGE THAT HAS BEEN MOVING WESTWARD IN TANDEM WITH THE CYCLONE. GLOBAL MODEL GUIDANCE IS IN EXCELLENT AGREEMENT THAT IT WILL CONTINUE TO DO SO FOR MOST OF THE FORECAST PERIOD...AND THE GUIDANCE IS VERY TIGHTLY CLUSTERED ON A WEST TO WEST-NORTHWEST TRACK FOR AT LEAST THE NEXT 72 HOURS. AFTER THAT...THE TRACK OF DEAN WILL DEPEND ON HOW MUCH INTERACTION THERE IS BETWEEN THE HURRICANE AND A MID- TO UPPER-LEVEL LOW CURRENTLY NORTHEAST OF THE BAHAMAS. ALL THE AVAILABLE GUIDANCE CURRENTLY MOVES THIS LOW WESTWARD OUT OF THE WAY AND SHOWS VERY LITTLE INTERACTION BETWEEN THE TWO...AND HENCE ONLY A MODEST RIGHTWARD BEND IN THE TRACK ON DAYS 4 AND 5. THE OFFICIAL FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS ADVISORY TRACK. GIVEN THE UNCERTAINTY IN GLOBAL MODEL FORECASTS AT LONG RANGES HOWEVER...A DIFFERENT EVOLUTION WITH THE UPPER LOW IS NOT OUT OF THE QUESTION. DEAN CONTINUES TO EXHIBIT A STRONG OUTFLOW PATTERN...AND THIS FAVORABLE UPPER FLOW IS EXPECTED TO PERSIST FOR THE NEXT TWO TO THREE DAYS. DATA FROM THE NOAA G-IV MISSION THIS EVENING SHOW NO EVIDENCE OF UNFAVORABLE THERMODYNAMICS IN THE NEAR ENVIRONMENT... AND THE AVAILABLE OBJECTIVE GUIDANCE INDICATES CONTINUED STRENGTHENING IN THE CARIBBEAN. THE UPPER FLOW COULD BE A LITTLE LESS FAVORABLE IN THE WESTERN CARIBBEAN...PARTICULARLY IF THE UPPER LOW LAGS A BIT. THE OFFICIAL FORECAST CALLS FOR SLIGHTLY FASTER DEVELOPMENT THAN THE PREVIOUS ADVISORY BUT ENDS UP IN THE SAME PLACE...AND IS IN GOOD AGREEMENT WITH THE AVAILABLE OBJECTIVE GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 17/0300Z 14.1N 58.7W 85 KT 12HR VT 17/1200Z 14.5N 61.9W 90 KT 24HR VT 18/0000Z 15.1N 65.8W 95 KT 36HR VT 18/1200Z 15.7N 69.2W 105 KT 48HR VT 19/0000Z 16.4N 72.6W 115 KT 72HR VT 20/0000Z 18.0N 80.0W 120 KT 96HR VT 21/0000Z 19.5N 86.0W 120 KT 120HR VT 22/0000Z 22.0N 92.0W 90 KT $$ FORECASTER FRANKLIN |
