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Tropical Depression SIX


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TROPICAL DEPRESSION SIX DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT SUN JUL 20 2003
 
TROPICAL DEPRESSION SIX IS A LITTLE BETTER ORGANIZED TONIGHT THAN 24
HR AGO.  WHILE THE LOW-LEVEL CENTER IS STILL POORLY DEFINED...
THERE HAS BEEN SOME INCREASE IN THE CONVECTIVE CURVATURE NEAR THE
CENTER.  SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB...AND 30
KT FROM SAB AND AFWA.  BASED ON THIS AND RECENT WARMING OF THE
CLOUD TOPS...THE SYSTEM WILL REMAIN A 30 KT DEPRESSION AT THIS
TIME.

THE INITIAL MOTION REMAINS 275/20.  THE DEPRESSION REMAINS ON THE
SOUTH SIDE OF THE STRONG ANTICYCLONE OVER THE CENTRAL ATLANTIC...
AND SHOULD REMAIN THERE FOR 72 HR OR SO.  THIS SHOULD CONTINUE A
BRISK WESTWARD OR WEST-NORTHWESTWARD MOTION.  ALL GUIDANCE AGREES
WITH THIS...AS WILL THE OFFICIAL FORECAST.  AFTER 72 HR...THE
FORECAST GETS TRICKIER AS THE CYCLONE APPROACHES A DE-AMPLIFYING
DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES.  WHILE DETAILS
DIFFER...THE GFS AND THE NOGAPS BUILD A PORTION OF THE ATLANTIC
RIDGE WESTWARD TOWARD FLORIDA.  IF THIS OCCURS...THE CYCLONE WOULD
LIKELY CONTINUE WEST-NORTHWEST AT A SLOWER SPEED.  THIS SCENARIO IS
CURRENTLY SUPPORTED BY MOST GUIDANCE...AND THE OFFICIAL FORECAST
GOES ALONG WITH IT.  AN ALTERNATE SCENARIO COMES FROM THE UKMET...
WHICH KEEPS ENOUGH OF A WEAKNESS TO TURN THE CYCLONE NORTHWESTWARD
THOUGH THE BAHAMAS AND JUST EAST OF FLORIDA.  THE UKMET IS
CURRENTLY A RIGHT OUTLIER...BUT CANNOT BE RULED OUT YET.

THE INTENSITY FORECAST IS PROBLEMATIC.  FIRST...THE CYCLONE IS
POORLY ORGANIZED.  SECOND...WHILE LARGE-SCALE MODELS BUILD AN
UPPER-LEVEL ANTICYCLONE WESTWARD TO PROVIDE A PATTERN FAVORABLE FOR
DEVELOPMENT...THE MODELS CONSISTENTLY OVERDID SUCH FORECASTS DURING
CLAUDETTE...AND CURRENT SATELLITE IMAGERY INDEED SHOWS THE CYCLONE
GETTING CLOSER TO SOUTHWESTERLY AND SOUTHERLY UPPER-LEVEL FLOW
WHICH COULD SLOW OR HALT DEVELOPMENT.  THIRD...AFTER 48 HR THE
SYSTEM WILL BE NEAR OR OVER HISPANIOLA AND CUBA...AND THE
DIFFERENCE BETWEEN NEAR AND OVER COULD HAVE HUGE IMPACTS ON THE
INTENSITY.  FINALLY...NONE OF THE INTENSITY GUIDANCE FORECASTS MUCH
DEVELOPMENT.  THE OFFICIAL INTENSITY FORECAST WILL COMPROMISE
BETWEEN THESE POSSIBILITIES BY FORECASTING SLOW STRENGTHENING FOR
48-72 HR...THEN LITTLE CHANGE UNTIL THE CYCLONE REACHES THE GULF OF
MEXICO.  HOWEVER...THIS IS A LOW CONFIDENCE INTENSITY FORECAST.

FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0300Z 13.7N  54.6W    30 KT
 12HR VT     21/1200Z 14.1N  57.6W    35 KT
 24HR VT     22/0000Z 15.0N  61.5W    40 KT
 36HR VT     22/1200Z 16.1N  65.4W    45 KT
 48HR VT     23/0000Z 17.2N  69.0W    50 KT
 72HR VT     24/0000Z 19.5N  76.0W    55 KT
 96HR VT     25/0000Z 22.0N  81.0W    55 KT
120HR VT     26/0000Z 24.5N  85.5W    60 KT
 
 
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