Tropical Depression TWELVE

ZCZC MIATCDAT2 ALL
TTAA00 KNHC DDHHMM
TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT THU SEP 04 2003
 
AIR FORCE RESERVE RECON REPORTS THIS EVENING...ALONG WITH SATELLITE
AND SURFACE REPORTS...INDICATE THAT TD-12 HAS CHANGED LITTLE. TWO
FLIGHTS THROUGH THE TIGHT LOW-LEVEL CIRCULATION CENTER INDICATED
SURFACE PRESSURES OF 1004 AND 1005 MB. THEREFORE...TD-12 IS BEING
MAINTAINED AS A 30-KT TROPICAL CYCLONE FOR THIS ADVISORY.
 
THE INITIAL MOTION ESTIMATE IS 090/06...BASED ON THE GENERAL TREND
IN THE RECON AND SATELLITE FIX POSITIONS. 05/00Z UPPER-AIR DATA
INDICATE THE DEPRESSION HAS ALREADY BEEN CAUGHT UP BY A BROAD
MID-LEVEL TROUGH OVER THE SOUTHEASTERN UNITED STATES. THERE ARE AT
LEAST 2 MORE SHORTWAVE TROUGHS UPSTREAM THAT SHOULD MOVE
SOUTHEASTWARD AND GRADUALLY ACT TO TURN THE DEPRESSION MORE
EAST-NORTHEASTWARD AND EVENTUALLY NORTHEASTWARD. THE DEPRESSION
CURRENTLY HAS A SHALLOW CIRCULATION...BUT A RECENT BURST OF DEEP
CONVECTION HAS DEVELOPED JUST EAST OF THE CENTER...AND THAT SHOULD
HELP TO STRENGTHEN THE VERTICAL CIRCULATION. THIS SHOULD CAUSE THE
DEPRESSION TO BE STEERED MORE BY THE DEEP-LAYER WEST-SOUTHWESTERLY
FLOW...WHICH IS SIMILAR TO WHAT THE GLOBAL MODELS ARE INDICATING.
THE OFFICIAL FORECAST TRACK IS A LITTLE TO THE RIGHT OF THE
PREVIOUS TRACK AND IS CLOSE TO THE GLOBAL MODEL CONSENSUS.
 
THE RECENT BURST OF CONVECTION NEAR AND JUST EAST OF THE CENTER MAY
BE THE START OF MORE PERSISTENT DEEP CONVECTIVE DEVELOPMENT...AND
POSSIBLY STEADY STRENGTHENING. THE SOUTHWESTERLY SHEAR IS FORECAST
TO WEAKEN SLIGHTLY IN 12 TO 24 HOURS...SO THE INTENSITY FORECAST
HAS BEEN INCREASED SLIGHTLY IN LINE WITH THE SHIPS INTENSITY MODEL.
 
THERE IS A LARGE AREA OF RAIN ASSOCIATED WITH THE DEPRESSION TO THE
EAST OF THE CENTER...AND THESE RAINS ARE ALREADY AFFECTING PORTIONS
OF FLORIDA.  REGARDLESS OF WHETHER THIS SYSTEM BECOMES A TROPICAL
STORM OR NOT...IT POSES A SIGNIFICANT RAINFALL/FLOODING THREAT.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/0300Z 27.7N  85.5W    30 KT
 12HR VT     05/1200Z 27.8N  84.4W    35 KT
 24HR VT     06/0000Z 28.3N  83.2W    45 KT
 36HR VT     06/1200Z 29.0N  81.9W    35 KT...INLAND
 48HR VT     07/0000Z 30.0N  80.5W    40 KT...OVER WATER
 72HR VT     08/0000Z 32.0N  78.3W    40 KT
 96HR VT     09/0000Z 34.0N  75.0W    35 KT
120HR VT     10/0000Z 36.0N  71.5W    35 KT
 
 
NNNN