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#109397 (Received by flhurricane at: 4:34 PM 07.Sep.2006) TCDAT1 TROPICAL STORM FLORENCE DISCUSSION NUMBER 17 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062006 500 PM EDT THU SEP 07 2006 FLORENCE REMAINS AN UNUSUALLY LARGE...NOW MORE THAN 900 NMI DIAMETER... NON-CLASSICAL TROPICAL CYCLONE. THE WIND FIELD WAS EXPANDED AGAIN...ESPECIALLY IN THE NORTHEASTERN QUADRANT...BASED ON SURROUNDING SHIP AND BUOY REPORTS. THE OUTER CONVECTIVE STRUCTURE HAS CHANGED LITTLE TODAY...WHEREAS INNER CORE CONVECTION HAS BEGUN TO DEVELOP OVER AND TO THE WEST OF THE CENTER FOR THE FIRST TIME. SINCE FLORENCE IS SUCH A LARGE SYSTEM...CONVECTIVE FLUCTUATIONS IN THE OUTER REGIONS LIKELY WILL HAVE LITTLE EFFECT ON THE WIND SPEEDS SINCE THE LATTER ARE DRIVEN MORE BY THE SHARP PRESSURE GRADIENT BETWEEN THE CYCLONE AND THE LARGE HIGH SITUATED TO THE NORTH. NOW THAT INNER CORE CONVECTION HAS DEVELOPED...STEADY STRENGTHENING IS FORECAST FOR THE NEXT 96 HOURS WITH SLOW WEAKENING EXPECTED AFTER THAT DUE TO INCREASING VERTICAL SHEAR AND COOLER WATERS. THE INITIAL MOTION ESTIMATE IS 300/12. FLORENCE REMAINS ON TRACK SO THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS TRACK FORECAST OR REASONING. THE GLOBAL MODELS REMAIN TIGHTLY CLUSTERED ON TAKING FLORENCE WEST-NORTHWESTWARD AROUND THE SOUTHERN PORTION OF THE SUBTROPICAL RIDGE THROUGH 72 HOURS...AND THEN TURNING THE CYCLONE NORTHWEST AND NORTHWARD INTO A BREAK IN THE RIDGE THAT IS FORECAST BY ALL THE MODELS TO DEVELOP IN 72-96 HOURS. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE PREVIOUS TRACK AND THE NHC MODEL CONSENSUS... AND BRINGS FLORENCE VERY NEAR BERMUDA IN ABOUT 96 HOURS. FORECAST POSITIONS AND MAX WINDS INITIAL 07/2100Z 20.6N 54.9W 45 KT 12HR VT 08/0600Z 21.5N 56.6W 50 KT 24HR VT 08/1800Z 22.8N 59.0W 55 KT 36HR VT 09/0600Z 24.0N 61.3W 65 KT 48HR VT 09/1800Z 25.2N 63.3W 75 KT 72HR VT 10/1800Z 28.1N 65.7W 90 KT 96HR VT 11/1800Z 32.0N 66.0W 95 KT...NEAR BERMUDA 120HR VT 12/1800Z 38.0N 63.5W 90 KT $$ FORECASTER STEWART |