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TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER 1
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT SAT SEP 21 2002
THE AREA OF DISTURBED WEATHER IN THE TROPICAL ATLANTIC ASSOCIATED
WITH A TROPICAL WAVE HAS BECOME BETTER ORGANIZED WITH DVORAK
CLASSIFICATIONS OF 2.0 FROM BOTH TAFB AND SAB. SHIP AND BUOY DATA
YESTERDAY ALSO HINTED THAT THERE WAS A BROAD LOW-LEVEL CIRCULATION
ASSOCIATED WITH THIS DISTURBANCE. EVEN THOUGH CONVECTION HAS
WEAKENED THIS AFTERNOON...VISIBLE SATELLITE IMAGES SHOW DEVELOPING
CURVED BANDING FEATURES BENEATH A WELL-DEFINED UPPER-LEVEL
ANTICYCLONE. THUS ADVISORIES ARE INITIATED ON TROPICAL DEPRESSION
THIRTEEN.
A FAVORABLE UPPER ENVIRONMENT IS EXPECTED TO CONTINUE OVER THE
DEPRESSION AS IT MOVES WESTWARD OVER PROGRESSIVELY WARMER WATERS AT
ABOUT 15 KNOTS. SHIPS MODEL BRINGS THE DEPRESSION UP TO 91 KNOTS IN
72 HOURS. THE OFFICIAL FORECAST IS LITTLE MORE CONSERVATIVE UNTIL
SOME SIGNALS OF SIGNIFICANT INTENSIFICATION ARE NOTED.
THE SYSTEM IS SOUTH OF A MIDDLE-LEVEL RIDGE OVER THE CENTRAL
ATLANTIC WHICH SHOULD PERSIST FOR THE MAJORITY OF THE FORECAST
PERIOD. HOWEVER...THIS RIDGE IS EXPECTED TO SLOWLY ERODE ON THE
WESTERN SIDE... PARTIALLY DUE TO KYLE... AND COULD INDUCE A MORE A
TRACK MORE TO THE NORTHWEST AFTER 48 HOURS. FOR NOW THE FORECAST
WILL STAY IN THE MIDDLE OF THE GUIDANCE ENVELOPE UNTIL ANY
INTERACTIONS BETWEEN THE CYCLONES BECOME MORE CLEAR.
FORECASTER AVILA/BLAKE
FORECAST POSITIONS AND MAX WINDS
INITIAL 21/2100Z 10.4N 45.7W 30 KTS
12HR VT 22/0600Z 10.5N 48.0W 30 KTS
24HR VT 22/1800Z 11.0N 51.0W 30 KTS
36HR VT 23/0600Z 11.5N 53.5W 40 KTS
48HR VT 23/1800Z 12.5N 56.5W 50 KTS
72HR VT 24/1800Z 14.5N 61.0W 65 KTS
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