Tropical Depression FIVE

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TROPICAL DEPRESSION FIVE DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052012
500 PM AST WED AUG 01 2012
 
DURING THE DAY...VISIBLE SATELLITE IMAGES SHOWED THAT THE LOW-LEVEL
CIRCULATION OF THE LOW PRESSURE SYSTEM TO THE EAST OF
THE WINDWARD ISLANDS HAS BECOME BETTER DEFINED.  DEEP CONVECTION
HAS PULSED A BIT...AND IS SOMEWHAT LACKING OVER THE NORTHERN PART
OF THE CIRCULATION.  HOWEVER THE SYSTEM HAS NOW ACQUIRED SUFFICIENT
ORGANIZATION TO BE CLASSIFIED AS A TROPICAL DEPRESSION.  THE
INITIAL WIND SPEED IS SET AT 30 KT IN ACCORDANCE WITH DVORAK
ESTIMATES FROM TAFB AND SAB.  FORECASTING INTENSITY CHANGE IS
ALWAYS A CHALLENGE...AND IS PARTICULARLY TRUE IN THIS CASE.
MODERATE VERTICAL SHEAR...ASSOCIATED WITH A LARGE UPPER-LEVEL LOW
TO THE NORTH OF THE DEPRESSION...IS LIKELY TO AFFECT THE SYSTEM FOR
THE NEXT COUPLE OF DAYS.  THUS ONLY SLOW STRENGTHENING IS
ANTICIPATED DURING THE FIRST HALF OF THE FORECAST PERIOD.  LATER
ON...THE INTENSITY FORECAST UNCERTAINTY INCREASES.  OUR BEST TWO
GLOBAL MODELS ARE AT ODDS AS TO HOW THE SYSTEM WILL EVOLVE AS IT
MOVES OVER THE CARIBBEAN.  THE GFS FORECASTS THE UPPER-LEVEL
ENVIRONMENT TO BECOME QUITE CONDUCIVE FOR STRENGTHENING BY THE END
OF THE FORECAST PERIOD...WHEREAS THE ECMWF MODEL SHOWS THE SYSTEM
DEGENERATING INTO A TROPICAL WAVE.  THE OFFICIAL FORECAST LEANS
TOWARD TO THE GFS...BUT TIME WILL TELL.
 
THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 285/16.  GLOBAL MODELS
DEPICT A STRONG MID-TROPOSPHERIC ANTICYCLONE TO THE NORTH OF THE
TROPICAL CYCLONE FOR THE NEXT SEVERAL DAYS.  THIS STEERING PATTERN
SHOULD CAUSE A WEST-NORTHWESTWARD TO WESTWARD MOTION AT ABOUT THE
SAME SPEED THROUGH MUCH OF THE FORECAST PERIOD.  A WEAKNESS OVER
THE GULF OF MEXICO COULD CAUSE SOME SLOWING AND BIT OF A
NORTHWESTWARD TURN LATE IN THE PERIOD.  THE COMPUTER MODELS ARE IN
GOOD AGREEMENT...AND THE NHC TRACK FORECAST IS NOT FAR FROM THE
MODEL CONSENSUS.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/2100Z 12.2N  49.0W   30 KT  35 MPH
 12H  02/0600Z 12.7N  51.3W   40 KT  45 MPH
 24H  02/1800Z 13.3N  54.5W   45 KT  50 MPH
 36H  03/0600Z 13.8N  57.7W   50 KT  60 MPH
 48H  03/1800Z 14.4N  60.9W   55 KT  65 MPH
 72H  04/1800Z 15.5N  67.0W   55 KT  65 MPH
 96H  05/1800Z 16.5N  73.0W   60 KT  70 MPH
120H  06/1800Z 17.5N  78.0W   65 KT  75 MPH
 
$$
FORECASTER PASCH/BLAKE
 
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