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#37635 (Received by flhurricane at: 10:40 AM 05.Aug.2005) TCDAT4 TROPICAL DEPRESSION NINE DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT FRI AUG 05 2005 HOW LITTLE WE KNOW ABOUT THE GENESIS OF TROPICAL CYCLONES. SATELLITE IMAGES DURING THE DAY YESTERDAY SHOWED A DISTINCT DISTURBANCE IN THE DEEP TROPICS WITH ALL KNOWN FACTORS APPARENTLY FAVORABLE FOR THE SYSTEM TO BECOME A TROPICAL STORM. SURPRISINGLY THIS MORNING...VISIBLE IMAGES INDICATE THAT THE SYSTEM HAS BECOME DISORGANIZED. UNEXPECTEDLY...THE LOW-LEVEL CIRCULATION MOVED NORTHWESTWARD TOWARD RELATIVELY COOLER WATERS AND LOST MOST OF THE DEEP CONVECTION. HOWEVER...THE SYSTEM STILL MAINTAINS A LARGE AND VIGOROUS ENVELOPE WITH AT LEAST 25 KNOTS. IT IS INTERESTING TO NOTE THAT THE LAST FEW GFS RUNS WERE DEVELOPING A TROPICAL CYCLONE FROM THIS SYSTEM AND MOVED IT WESTWARD THROUGH THE ATLANTIC. HOWEVER...IN THE LATEST 6Z GFS RUN...THERE IS NO TROPICAL CYCLONE DEVELOPMENT. THE GFDL...LIKE THE GFS...ALSO CHANGED ITS TUNE AT 6Z AND NOW EVEN SHOWS DISSIPATION IN 48 HOURS. GIVEN THESE DRASTIC CHANGES SEEN IN GFS...THE OFFICIAL FORECAST ALSO MAKES A DRASTIC CHANGE IN BOTH TRACK AND INTENSITY. THE SYSTEM IS NOW KEPT AS A 25-KNOT TROPICAL DEPRESSION FOR A COUPLE OF DAYS. THEREAFTER...A MODEST DEVELOPMENT IS ANTICIPATED WHEN THE CYCLONE REACHES WARMER WATERS...IF IT SURVIVES. THE OFFICIAL FORECAST HAS BEEN SHIFTED SUBSTANTIALLY NORTHWARD FROM THE PREVIOUS ADVISORY. FORECASTER AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 05/1500Z 16.4N 37.3W 25 KT 12HR VT 06/0000Z 17.5N 39.0W 25 KT 24HR VT 06/1200Z 18.5N 41.5W 25 KT 36HR VT 07/0000Z 19.5N 43.5W 30 KT 48HR VT 07/1200Z 20.5N 45.0W 30 KT 72HR VT 08/1200Z 23.0N 48.0W 30 KT 96HR VT 09/1200Z 26.5N 52.0W 35 KT 120HR VT 10/1200Z 30.0N 55.0W 35 KT |