|
Show Selection: |
| #41519 (Received by flhurricane at: 11:03 PM 23.Aug.2005) TCDAT2 TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT TUE AUG 23 2005 THE RECONNAISSANCE AIRCRAFT... PRIOR TO DEPARTING THE DEPRESSION AFTER ABOUT 2230Z... CONTINUED TO REPORT A MINIMUM CENTRAL PRESSURE NEAR 1007 MB... AND MAXIMUM FLIGHT LEVEL WINDS DURING THIS MISSION NEVER EXCEEDED THE 39 KT OBSERVED SHORTLY AFTER 18Z. DURING THE PAST COUPLE OF HOURS... THE CENTER HAS BEEN NEAR GEORGETOWN ON GREAT EXUMA ISLAND IN THE CENTRAL BAHAMAS... WHERE 1007 MB AND NEARLY CALM WINDS HAVE RECENTLY BEEN REPORTED. LACKING ANY DATA TO SUPPORT A STRONGER SYSTEM... THE ADVISORY INTENSITY IS MAINTAINED AT 30 KT. HOWEVER... RECENTLY A BAND OF DEEP CONVECTION... WITH SOME TOPS COLDER THAN -80C... HAS STRENGTHENED TO THE EAST OF THE CIRCULATION CENTER... AND THIS BAND COULD WRAP SUFFICIENTLY AROUND THE CENTER WITHIN THE NEXT SEVERAL HOURS. RADAR IMAGERY FROM GREAT EXUMA ALSO DEPICTS A NEARLY CONTINUOUS CURVED BAND OF RAINFALL BENEATH THESE CONVECTIVE TOPS. THE EARLIER AIRCRAFT FIXES SUGGESTED THAT THE DEPRESSION WAS MOVING ERRATICALLY. BASED ON CONTINUITY AND ON SURFACE OBSERVATIONS FROM THE BAHAMAS... THE INITIAL MOTION ESTIMATE IS 305/6 KT... A LITTLE SLOWER THAN BEFORE. THE WEAK STEERING CURRENTS ARE A RESULT OF THE DEPRESSION LYING TO THE SOUTH OF A NARROW MID LEVEL RIDGE AXIS ORIENTED EAST TO WEST BETWEEN BERMUDA AND NORTHERN FLORIDA. SINCE MOST OF THE DYNAMICAL MODELS DO NOT FORECAST THIS RIDGE TO STRENGTHEN MUCH OFF THE U.S. EAST COAST DURING THE NEXT FEW DAYS... A SLOW MOTION IS ANTICIPATED THROUGHOUT THE FORECAST PERIOD... WITH A WESTWARD BEND BEYOND ABOUT 36 HOURS. MOST OF THE DYNAMICAL GUIDANCE... EXCEPT FOR THE GFS... GENERALLY AGREE WITH THIS SCENARIO. THE GFS CONTINUES TO BE THE SINGLE OUTLIER FORECASTING THAT THIS SYSTEM WILL STALL OVER FLORIDA BEYOND ABOUT 48 HOURS. THE NEW OFFICIAL FORECAST IS A LITTLE SLOWER AND TO THE RIGHT OF THE PREVIOUS ADVISORY... TO COME INTO BETTER AGREEMENT WITH THE MODEL CONSENSUS. GIVEN THE SLOW TREND THIS EVENING TOWARD INCREASED ORGANIZATION... THE DEPRESSION COULD BECOME A TROPICAL STORM EARLY ON WEDNESDAY MORNING. BEYOND THAT TIME... THE INTENSITY FORECAST IS PROBLEMATIC FOR MANY REASONS... NOT THE LEAST OF WHICH IS WIDELY DIFFERING MODEL GUIDANCE. THE GFDL STILL DOES NOT EVEN FORECAST STRENGTHENING TO A TROPICAL STORM. HOWEVER... THE SHIPS MODEL STILL INSISTS ON HURRICANE INTENSITY BY 48 HOURS BEFORE THE SYSTEM CROSSES FLORIDA... WITHIN AN ENVIRONMENT OF MODEST WIND SHEAR AND OVER VERY WARM SSTS. AS MORE OF A COMPROMISE BETWEEN THESE SOLUTIONS... BUT STILL LEANING TOWARD THE SHIPS... THE OFFICIAL FORECAST IS JUST A LITTLE MORE CONSERVATIVE THAN THE PREVIOUS ADVISORY... BUT STILL CALLS FOR A STRONG TROPICAL STORM TO APPROACH FLORIDA WITHIN THE NEXT COUPLE OF DAYS. SINCE TROPICAL STORM FORCE WINDS COULD BE VERY CLOSE TO THE SOUTHEAST COAST OF FLORIDA AND THE NORTHERN FLORIDA KEYS IN ABOUT 36 HOURS... A TROPICAL STORM WATCH HAS BEEN ISSUED AT THIS TIME. A TROPICAL STORM WARNING AND PERHAPS A HURRICANE WATCH COULD BE ISSUED ON WEDNESDAY IF THE DEPRESSION STRENGTHENS MORE RAPIDLY THAN CURRENTLY FORECAST. THE UNCERTAINTY IN THIS FORECAST... AND THE POTENTIAL IMPACTS OF THIS TROPICAL CYCLONE... ARE QUANTIFIED IN AN EXPERIMENTAL NHC TEXT PRODUCT ISSUED WITH THIS AND EVERY ADVISORY PACKAGE DURING 2005. THIS PRODUCT PROVIDES WIND SPEED PROBABILITIES AT SPECIFIC LOCATIONS. THE PROBABILITIES OF EXPERIENCING TROPICAL STORM FORCE WINDS FROM THIS SYSTEM DURING THE NEXT FIVE DAYS ARE SIMILAR AT EACH INDIVIDUAL LOCATION THROUGHOUT THE TROPICAL STORM WATCH AREA. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 24/0300Z 23.4N 76.0W 30 KT 12HR VT 24/1200Z 24.2N 76.7W 35 KT 24HR VT 25/0000Z 25.1N 77.7W 40 KT 36HR VT 25/1200Z 25.7N 78.5W 45 KT 48HR VT 26/0000Z 26.1N 79.5W 55 KT 72HR VT 27/0000Z 26.5N 81.5W 40 KT...INLAND 96HR VT 28/0000Z 27.0N 83.5W 55 KT 120HR VT 29/0000Z 27.5N 85.5W 65 KT |
