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#4108 (Received by flhurricane at: 4:53 AM 10.Aug.2004) TCDAT2 TROPICAL STORM BONNIE DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT TUE AUG 10 2004 IN SATELLITE IMAGERY...BONNIE REMAINS A RATHER UNIMPRESSIVE TROPICAL CYCLONE...WITH A SMALL CDO...CENTRAL DENSE OVERCAST...AND BANDING THAT IS LIMITED BUT INCREASING. THE CENTRAL CONVECTION HAS BEEN RATHER PERSISTENT THOUGH...AND DATA FROM A RECONNAISSANCE AIRCRAFT CURRENTLY INVESTIGATING BONNIE SHOWS THAT THE CYCLONE IS MAINTAINING ITS ORGANIZATION AND STRENGTH. THE CREW REPORTED A 10 MILE WIDE EYE...ALMOST UNHEARD OF IN A SYSTEM OF THIS INTENSITY. THE PEAK FLIGHT-LEVEL WINDS WERE 49 KT...AND A DROPSONDE IN THE SOUTHEAST QUADRANT REPORTED SURFACE WINDS OF 43 KT. BASED ON THESE DATA...THE INITIAL INTENSITY ESTIMATE IS HELD AT 45 KT FOR THIS ADVISORY. SMALL TROPICAL CYCLONES SUCH AS BONNIE ARE PRONE TO RAPID CHANGES IN INTENSITY...EITHER UP OR DOWN. THERE ARE A COUPLE OF FACTORS THAT WOULD ARGUE FOR SUBSTANTIAL STRENGTHENING OVER THE NEXT DAY OR TWO. FIRST...ALTHOUGH BONNIE IS CURRENTLY EXPERIENCING SOME NORTHERLY SHEAR...IT SHOULD BE MOVING UNDER LIGHT ANTICYCLONIC FLOW IN THE CENTRAL GULF LATER TODAY. SECOND...THE FORECAST TRACK TAKES BONNIE OVER OR VERY NEAR A POOL OF DEEP WARM WATER IN THE NORTH-CENTRAL GULF. A MITIGATING FACTOR WOULD BE THE RELATIVELY DRY AIR IN THE NORTHWESTERN GULF. THE LAST TWO RUNS OF BOTH THE GFDL AND SHIPS MODELS MAKE BONNIE A HURRICANE PRIOR TO LANDFALL. THE GFS DOES NOT SHOW INTENSIFICATION...BUT IN FACT BARELY ACKNOWLEDGES BONNIE'S EXISTENCE DUE TO THE CYCLONE'S SMALL SIZE. THE OFFICIAL FORECAST IS ADJUSTED UPWARD FROM THE PREVIOUS ADVISORY...AND CALLS FOR BONNIE TO REACH HURRICANE STRENGTH WITHIN 48 HOURS. HOWEVER...IT IS STILL BELOW THE SHIPS GUIDANCE...AND IS CONSIDERABLY BELOW THE GFDL GUIDANCE. THE CURRENT MOTION ESTIMATE IS 295/7...SOMEWHAT TO THE LEFT OF THE PREVIOUS TRACK. MOST OF THE 3-DIMENSIONAL DYNAMICAL GUIDANCE TURNS BONNIE SHARPLY NORTHWARD AND THEN NORTHEASTWARD AHEAD OF A MID-LEVEL TROUGH ABOUT TO ENTER THE WESTERN GULF. THE OFFICIAL FORECAST IS ADJUSTED A LITTLE TO THE LEFT OF THE PREVIOUS TRACK FOR THE FIRST 24 HOURS...IS FAIRLY SIMILAR THEREAFTER...AND IS IN BEST AGREEMENT WITH THE GFDL GUIDANCE. THE NOAA G-IV JET WILL CONDUCT A MISSION IN THE ENVIRONMENT OF BONNIE THIS EVENING TO IMPROVE THE INITIAL CONDITION FOR THE NUMERICAL TRACK GUIDANCE MODELS. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 10/0900Z 23.6N 90.1W 45 KT 12HR VT 10/1800Z 24.2N 90.7W 50 KT 24HR VT 11/0600Z 25.5N 90.7W 55 KT 36HR VT 11/1800Z 26.6N 89.8W 60 KT 48HR VT 12/0600Z 28.0N 88.0W 65 KT 72HR VT 13/0600Z 33.5N 81.0W 25 KT...INLAND 96HR VT 14/0600Z...ABSORBED INTO FRONTAL ZONE |