ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006 1100 AM EDT TUE SEP 12 2006 THE CLOUD PATTERN ASSOCIATED WITH THE TROPICAL WAVE THAT EMERGED FROM AFRICA YESTERDAY HAS BECOME SIGNIFICANTLY BETTER ORGANIZED THIS MORNING. A FAIRLY WELL-DEFINED CURVED CONVECTIVE BAND HAS FORMED OVER THE WESTERN SEMICIRCLE OF THE SYSTEM AND DVORAK CLASSIFICATIONS ARE AT T1.5 FROM TAFB AND SAB. TWO REPORTS OF NORTHERLY 19 KT AND SOUTHERLY 10 KT WINDS...FROM SHIPS WITH CALL SIGNS PBCJ AND UCAB RESPECTIVELY...CONFIRM THE PRESENCE OF A CLOSED SURFACE CIRCULATION. BASED ON THE ABOVE DATA...ADVISORIES ARE BEING INITIATED ON TROPICAL DEPRESSION EIGHT. PRESENTLY THE SYSTEM APPEARS TO BE IN AN ENVIRONMENT OF WEAK EASTERLY SHEAR AND IT SHOULD BE TRAVERSING SEA SURFACE TEMPERATURES OF AROUND 28C. HOWEVER...WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL TROUGH NEAR 40W-45W NORTH OF 15N AND THE GLOBAL MODELS INDICATE THAT THIS FEATURE WILL PERSIST FOR THE NEXT COUPLE OF DAYS. IF THIS SCENARIO VERIFIES...THE ENVIRONMENT COULD BECOME LESS CONDUCIVE FOR STRENGTHENING. THE OFFICIAL FORECAST SHOWS ONLY SLOW STRENGTHENING OVER THE NEXT COUPLE OF DAYS BUT PRESUMES THAT THE CYCLONE WILL BE ABLE TO EVENTUALLY STRENGTHEN INTO A HURRICANE. THIS OFFICIAL FORECAST IS SOMEWHAT LOWER THAN THE CURRENTLY AVAILABLE INTENSITY GUIDANCE. INITIAL MOTION IS ESTIMATED TO BE 270/16. OVER THE NEXT SEVERAL DAYS...THE CYCLONE IS LIKELY TO BE STEERED BY EASTERLY FLOW TO THE SOUTH OF A MID-LEVEL SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC. LATER IN THE FORECAST PERIOD....THERE ARE DIFFERENCES OF OPINION AMONGST THE DYNAMICAL TRACK PREDICTION MODELS. THE U.K. MET OFFICE AND ECMWF GLOBAL MODELS TURN THE SYSTEM NORTHWARD TO THE EAST OF 50W...WHEREAS THE GFS FORECASTS LESS OF A WEAKNESS IN THE RIDGE NEAR 50W AND TAKES THE SYSTEM FARTHER SOUTH AND WEST. THE OFFICIAL TRACK FORECAST IS BETWEEN THESE POSSIBILITIES AND FAIRLY CLOSE TO THE TRACK DEPICTED IN THE 0600 UTC GFDL RUN. THIS MORNING...DROPSONDES ARE BEING LAUNCHED FROM A DC-8 AIRCRAFT IN THE VICINITY OF THE SYSTEM AS PART OF THE AFRICAN MONSOON MULTIDISCIPLINARY ANALYSIS PROJECT...AMMA. THESE SOUNDING DATA ARE BEING INCORPORATED INTO THE GLOBAL TELECOMMUNICATIONS SYSTEM AND...HOPEFULLY...INTO THE GLOBAL MODELS TO IMPROVE THE INITIALIZATION OF THIS TROPICAL CYCLONE. FORECAST POSITIONS AND MAX WINDS INITIAL 12/1500Z 12.5N 23.0W 25 KT 12HR VT 13/0000Z 12.7N 25.3W 30 KT 24HR VT 13/1200Z 13.0N 28.4W 35 KT 36HR VT 14/0000Z 13.5N 31.5W 40 KT 48HR VT 14/1200Z 14.0N 34.8W 50 KT 72HR VT 15/1200Z 15.5N 41.5W 65 KT 96HR VT 16/1200Z 17.0N 47.0W 75 KT 120HR VT 17/1200Z 19.0N 51.0W 85 KT $$ FORECASTER PASCH NNNN
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Page last modified: Tuesday, 12-Sep-2006 14:35:01 UTC