Tropical Depression FOUR

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TROPICAL DEPRESSION FOUR DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT FRI AUG 13 2004
 
CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE THAT THE
TROPICAL DISTURBANCE LOCATED ABOUT 240 NMI SOUTH-SOUTHEAST OF THE
CAPE VERDE ISLANDS HAS BECOME MUCH BETTER ORGANIZED THIS MORNING.
THE SYSTEM IS BEING UPGRADED TO TROPICAL DEPRESSION FOUR BASED ON A
CONSENSUS DVORAK SATELLITE INTENSITY ESTIMATE OF T2.0...OR 30 KT...
FROM TAFB AND SAB...AND IMPROVED BANDING FEATURES. UPPER-LEVEL
OUTFLOW IS GOOD IN THE SOUTHERN SEMICIRCLE AND FAIR ELSEWHERE.

THE INITIAL MOTION ESTIMATE IS 280/13. LOCATING THE EXACT CENTER IS
DIFFICULT AT THIS TIME DUE TO CONTINUED REORGANIZATION OF THE
CENTRAL DEEP CONVECTION. HOWEVER...THE GENERAL MOTION SHOULD BE
WESTWARD FOR THE NEXT 24 TO 36 HOURS AS THE CYCLONE IS STEERED BY
THE DEEP EASTERLY FLOW TO NORTH. BY 48 HOURS...ALL THE GLOBAL
MODELS AGREE ON A MID-LEVEL TROUGH DIGGING SOUTHEASTWARD BETWEEN
35-40W LONGITUDE...WHICH SHOULD WEAKEN THE SUBTROPICAL RIDGE. A
SMALL POLEWARD STAIR-STEP IN THE TRACK MAY OCCUR AT THAT TIME...
AFTER WHICH A RETURN TO A MORE WESTWARD MOTION IS EXPECTED AS THE
TROUGH LIFTS OUT TO THE NORTHEAST OF THE CYCLONE.

BASED ON THE FORECAST TRACK...THE DEPRESSION IS EXPECTED TO MOVE
NORTH OF THE WARMEST WATER IN 36 TO 48 HOURS. THIS WILL ALSO PLACE
THE SYSTEM DEEPER INTO THE COOLER AND MORE STABLE TRADE WIND FLOW
THAT EXISTS EAST OF 50W LONGITUDE. AS SUCH...ONLY MODEST
INTENSIFICATION IS EXPECTED THROUGHOUT THE FORECAST PERIOD.
HOWEVER...IF THE CYCLONE TAKES A MORE SOUTHERLY TRACK AND STAYS
OVER WARMER WATER...THEN IT COULD BECOME A HURRICANE BY 72 HOURS.
THE INTENSITY FORECAST IS CLOSE TO THE SHIPS INTENSITY MODEL.
 
FORECASTER STEWART
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 12.2N  22.7W    30 KT
 12HR VT     14/0000Z 12.4N  24.5W    35 KT
 24HR VT     14/1200Z 12.8N  27.0W    40 KT
 36HR VT     15/0000Z 13.3N  29.5W    45 KT
 48HR VT     15/1200Z 14.0N  32.0W    50 KT
 72HR VT     16/1200Z 15.5N  36.5W    55 KT
 96HR VT     17/1200Z 16.5N  41.0W    60 KT
120HR VT     18/1200Z 17.0N  46.5W    60 KT
 
 
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