[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 051437
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


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