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TROPICAL DEPRESSION SEVEN-E DISCUSSION NUMBER 1
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT SUN AUG 26 2001
SATELLITE IMAGERY SHOWS THAT THE AREA OF DISTURBED WEATHER OFF THE
SOUTHEST COAST OF MEXICO HAS BECOME BETTER ORGANIZED. THERE IS GOOD
ROTATION...AND BANDING FEATURES ARE BECOMING BETTER DEFINED.
ALSO...A TRMM SATELLITE OVERPASS AT 311 UTC INDICATE THAT A
POORLY-DEFINED CIRCULATION CENTER HAS DEVELOPED. THE SYSTEM IS
BEING UPGRADED TO A TROPICAL DEPRESSION AT THIS TIME. VERTICAL
SHEAR OVER THE AREA APPEARS TO BE FAIRLY WEAK AND THE SST IS NEAR 29
DEG C. THEREFORE...STRENGTHENING IS FORECAST. THE OFFICIAL WIND
SPEED FORECAST IS RATHER CONSERVATIVE...OWING TO THE UNCERTAINTIES
IN INTENSITY PREDICTION.
AT FIRST GLANCE...THE TRACK FORECAST SEEMS STRAIGHTFORWARD. THE
GLOBAL MODELS...AVN...U.K. MET...AND NOGAPS...ALL SHOW A PRONOUNCED
500 MB RIDGE TO THE NORTH OF THE TROPICAL CYCLONE FOR THE NEXT
COUPLE OF DAYS. HOWEVER THESE SAME MODELS REFUSE TO MOVE THE
CYCLONE VERY MUCH TO THE WEST. APPARENTLY THE DEPRESSION IS
EMBEDDED WITHIN A BROAD LOW- TO MID-LEVEL CYCLONIC CIRCULATION TO
THE SOUTH OF THE RIDGE. THUS THE SOUTHWESTERLY FLOW ON THE
SOUTHEAST SIDE OF THE BROAD CYCLONIC CIRCULATION COULD COUNTERACT
THE WESTWARD STEERING DUE TO THE SUBTROPICAL RIDGE. IN PARTIAL
DEFERENCE TO THE GLOBAL MODELS...THE OFFICIAL FORECAST SLOWS THE
FORWARD MOTION SIGNIFICANTLY OVER THE NEXT FEW DAYS.
FORECASTER PASCH
FORECAST POSITIONS AND MAX WINDS
INITIAL 26/0900Z 19.1N 108.9W 30 KTS
12HR VT 26/1800Z 19.6N 110.3W 35 KTS
24HR VT 27/0600Z 20.0N 112.2W 40 KTS
36HR VT 27/1800Z 20.0N 114.0W 45 KTS
48HR VT 28/0600Z 20.0N 115.5W 50 KTS
72HR VT 29/0600Z 20.0N 117.5W 60 KTS
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