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Tropical Depression EIGHT


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TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082007
500 AM EDT THU SEP 13 2007
 
SATELLITE IMAGES AND MICROWAVE DATA INDICATE THAT THE CLOUD PATTERN
HAS NOT BECOME ANY BETTER ORGANIZED DURING THE PAST FEW HOURS AND
THE LOW-LEVEL CENTER IS LOCATED TO THE NORTH OF A LARGE CIRCULAR
AREA OF DEEP CONVECTION. INITIAL INTENSITY REMAINS AT 30 KNOTS. THE
DEPRESSION STILL HAS THE OPPORTUNITY TO BECOME A TROPICAL STORM
SINCE THE SHEAR IS EXPECTED TO DECREASE IN THE NEXT DAY OR SO.
THEREAFTER...ALL GLOBAL MODELS FORECAST STRONG UPPER-LEVEL
WESTERLIES OVER THE EASTERN CARIBBEAN AND THE ADJACENT ATLANTIC
WATERS ASSOCIATED WITH A STRONGER THAN NORMAL UPPER-LEVEL TROUGH.
THIS PATTERN IS LIKELY TO INHIBIT THE DEPRESSION FROM
STRENGTHENING SIGNIFICANTLY. WEAKENING IS INDICATED BY THE END OF
THE FORECAST PERIOD AS THE CYCLONE APPROACHES THE AREA WELL TO THE
NORTHEAST OF THE LEEWARD ISLANDS WHERE THE SHEAR IS EXPECTED TO BE
LARGE.
 
THE DEPRESSION IS MOVING TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT
9 KNOTS AROUND A WEAK MID-LEVEL HIGH PRESSURE SYSTEM. SINCE STEERING
CURRENTS ARE FORECAST TO FURTHER WEAKEN...THE DEPRESSION IS
EXPECTED TO DECREASE IN FORWARD SPEED DURING THE NEXT 12 TO 24
HOURS. THE CYCLONE SHOULD THEN CONTINUE ON THIS GENERAL SLOW
WEST-NORTHWEST TRACK THROUGH 5 DAYS.  TRACK GUI DACE IS IN GOOD
AGREEMENT BRINGING THE CYCLONE ON A SLOW WEST-NORTHWEST MOTION AND
WEAKENING. THE UK AND ECMWF MODELS KEEP THE CYCLONE A LITTLE BIT
LONGER BUT THIS IS NOT REALISTIC GIVEN THE ANTICIPATED HIGHLY
UNFAVORABLE UPPER-LEVEL ENVIRONMENT AHEAD OF THE CYCLONE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0900Z 13.9N  47.5W    30 KT
 12HR VT     13/1800Z 14.5N  48.8W    35 KT
 24HR VT     14/0600Z 14.8N  49.6W    40 KT
 36HR VT     14/1800Z 15.0N  50.5W    45 KT
 48HR VT     15/0600Z 15.5N  51.5W    45 KT
 72HR VT     16/0600Z 16.5N  54.0W    45 KT
 96HR VT     17/0600Z 17.5N  57.0W    40 KT
120HR VT     18/0600Z 19.0N  60.0W    35 KT
 
$$
FORECASTER AVILA
 
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