Tropical Depression SIX

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TROPICAL DEPRESSION SIX DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062010
500 PM EDT SAT AUG 21 2010
 
SATELLITE IMAGES INDICATE THAT THE AREA OF LOW PRESSURE SOUTHWEST OF
THE CAPE VERDE ISLANDS HAS BECOME CONSIDERABLY BETTER ORGANIZED
DURING THE PAST SEVERAL HOURS. THE LOW APPEARS TO HAVE BECOME
MORE SEPARATED FROM THE LARGE AREA OF SOUTHWESTERLY FLOW WHICH HAS
BEEN PRESENT OVER THE TROPICAL ATLANTIC FOR THE PAST SEVERAL
DAYS....THOUGH IT IS STILL A BIT ELONGATED TO THE NORTHEAST. A LONG
CURVED BAND OF CONVECTION ALSO WRAPS AROUND THE SOUTHERN AND
WESTERN SEMICIRCLE. THE INITIAL INTENSITY WILL BE 25 KT...WHICH
AGREES WITH DVORAK CLASSIFICATIONS FROM TAFB/SAB OF T1.5...25
KT...AND A 25 KT ASCAT PASS FROM THIS MORNING.
 
A LARGE UPPER-LEVEL ANTICYCLONE IS FORECAST TO BE NEAR THE
DEPRESSION...WHICH SHOULD CAUSE ONLY WEAK TO MODERATE NORTHEASTERLY
SHEAR FOR THE NEXT SEVERAL DAYS. COMBINED WITH WARM SSTS...AT LEAST
STEADY STRENGTHENING IS EXPECTED UNTIL THE END OF THE FORECAST
PERIOD. BY THAT TIME...SOME INCREASE IN SOUTHWESTERLY SHEAR IS
POSSIBLE AS THE CYCLONE APPROACHES THE MID-OCEANIC TROUGH.  THE
INTENSITY GUIDANCE IS IN RELATIVELY GOOD AGREEMENT FOR SUCH A WEAK
SYSTEM WITH ALL RELIABLE GUIDANCE MAKING THE DEPRESSION A HURRICANE
WITHIN A FEW DAYS. THE NHC FORECAST IS CLOSE TO THE SHIPS/LGEM
MODELS...SHOWING A LARGE POWERFUL HURRICANE OVER THE CENTRAL
ATLANTIC OCEAN IN A FEW DAYS.
 
THE INITIAL MOTION ESTIMATE IS 285/7. A WEST-NORTHWEST MOTION WITH
INCREASING FORWARD SPEED IS EXPECTED AS THE DEPRESSION LEAVES THE
STRONG WESTERLY LOW-LEVEL FLOW ENVIRONMENT OF THE TROPICAL ATLANTIC
AND BECOMES STEERED BY A RIDGE OVER THE CENTRAL ATLANTIC OCEAN.
MOST OF THE MODELS SHOW THE CYCLONE TURNING TOWARD THE NORTHWEST
DUE TO A WEAKNESS IN THE RIDGE ALONG 50W IN ABOUT 3 DAYS. MODEL
GUIDANCE IS FAIRLY CLUSTERED AROUND THIS SOLUTION...WITH THE BIG
OUTLIERS TO THE NORTHEAST BEING THE CMC AND THE ECMWF MODELS. THESE
MODELS SHOW THE SYSTEM MOVING NORTHWEST SOON...WHICH ALLOWS THE
SYSTEM TO RECURVE TOWARD THE NORTH DUE TO A TROUGH ALONG 50W. THE
OFFICIAL FORECAST IS CLOSE TO...BUT SLIGHTLY TO THE LEFT OF...THE
DYNAMICAL MODEL CONSENSUS.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/2100Z 11.0N  32.1W    25 KT
 12HR VT     22/0600Z 11.5N  33.2W    35 KT
 24HR VT     22/1800Z 12.6N  35.4W    45 KT
 36HR VT     23/0600Z 13.6N  38.2W    55 KT
 48HR VT     23/1800Z 14.4N  41.4W    65 KT
 72HR VT     24/1800Z 17.5N  47.5W    85 KT
 96HR VT     25/1800Z 21.0N  52.0W    95 KT
120HR VT     26/1800Z 24.5N  55.5W    95 KT
 
$$
FORECASTER BLAKE
 
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