374 
 WTNT42 KNHC 232108
 TCDAT2
 TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER   1
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 5 PM EDT TUE AUG 23 2005
  
 DATA FROM AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT...ALONG
 WITH OBSERVATIONS FROM THE BAHAMAS AND NEARBY SHIPS...INDICATE THE
 BROAD LOW PRESSURE AREA OVER THE SOUTHEASTERN BAHAMAS HAS BECOME
 ORGANIZED ENOUGH TO BE CLASSIFIED AS TROPICAL DEPRESSION TWELVE.
 THE INITIAL INTENSITY OF 30 KT IS BASED RECON WINDS OF 39 KT AT 800
 FT...AND SHIP A8CI9 REPORTING 30-KT SUSTAINED WINDS AT 18Z IN THE
 NORTHEAST QUADRANT. UPPER-LEVEL OUTFLOW IS WEAK...BUT IMPROVING AS
 A SMALL ANTICYCLONE HAS BEEN DEVELOPING ABOVE THE LOW-LEVEL CENTER.
 
 THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 310/07. THE LOW-LEVEL
 CENTER HAS BEEN REFORMING WITHIN A LARGE CLEAR AREA NOTED IN
 SATELLITE IMAGERY. HOWEVER...FLIGHT-LEVEL RECON WINDS CLEARLY
 INDICATE A BROAD BUT OTHERWISE WELL-DEFINED LOW-LEVEL WIND FIELD.
 THERE HAVE BEEN SEVERAL SMALL VORTICES DEVELOP WITHIN THE
 CONVECTION IN THE EASTERN SEMICIRCLE AND THEN ROTATE WESTWARD OUT
 FROM UNDER THE CONVECTION. THE INITIAL POSITION IS ROUGHLY THE
 GEOMETRIC CENTER OF ALL THE SMALL SWIRLS...BUT SOME RE-ORGANIZATION
 OF THE CENTER WITHIN THE CONVECTION IS POSSIBLE. TD-12 IS EXPECTED
 TO CONTINUE MOVING SLOWLY NORTHWESTWARD TOWARD A WEAKNESS IN THE
 MID-LEVEL SUBTROPICAL RIDGE. THIS WEAKNESS SHOWS UP BEST IN 500 MB
 DATA...AND THEN DISAPPEARS BELOW AND ABOVE THAT LEVEL. BY 36-48
 HOURS...ALL OF THE GLOBAL MODELS AND THE GFDL MODEL FORECAST THE
 WEAKNESS TO FILL AND BE REPLACED BY A BROAD EAST-WEST ORIENTED
 RIDGE. THIS SHOULD HELP TO DRIVE THE CYCLONE MORE WESTWARD ACROSS
 SOUTHERN FLORIDA IN 60-72 HOURS...AND THEN INTO THE EASTERN GULF OF
 MEXICO BY 96 HOURS. THIS SCENARIO IS CONSISTENT WITH THE NHC MODEL
 CONSENSUS AND THE DEVELOPING SYNOPTIC PATTERN.
 
 THE INTENSITY FORECAST IS A LITTLE TRICKY DUE TO THE UNCERTAINTY ON
 EXACTLY WHEN A WELL-DEFINED CENTER WILL DEVELOP AND HOW SOON
 CONVECTION WRAPS AROUND THE WEST SIDE OF THE CIRCULATION. THE
 UPPER-LEVEL FLOW IS FORECAST TO REMAIN STRONGLY DIFLUENT FROM THE
 NORTH FOR THE NEXT 24-36 HOURS...AND THEN BECOME NORTHEASTERLY TO
 EASTERLY AFTER THAT. SINCE THE SHEAR IS ALSO FORECAST TO REMAIN
 RELATIVELY LOW AT AROUND 10 KT AND SSTS WILL BE NEAR 31C UNDER THE
 CENTER...AT LEAST STEADY INTENSIFICATION APPEARS TO BE IN ORDER. IF
 CENTRAL CONVECTION DEVELOPS WITHIN THE NEXT 24 HOURS...THEN THIS
 SYSTEM COULD REACH HURRICANE STRENGTH BEFORE IT MAKES LANDFALL. THE
 OFFICIAL INTENSITY FORECAST IS SLIGHTLY LOWER THAN THE SHIPS MODEL.
  
 THE NWS RULES GOVERNING THE NAMING OF TROPICAL CYCLONES SPECIFY
 THAT...WITHIN A BASIN...WHEN A CYCLONE FORMS FROM THE REMNANT OF A
 PREVIOUSLY EXISTING CYCLONE...THE OLD NAME/NUMBER IS RETAINED.
 TROPICAL DEPRESSION TWELVE HAS A COMPLEX GENESIS THAT LIKELY
 INCLUDES A MID-LEVEL REMNANT OF FORMER TROPICAL DEPRESSION TEN. A
 REVIEW OF SATELLITE AND RAWINSONDE DATA OVER THE PAST WEEK OR SO
 SUGGESTS THAT A SECOND DISTURBANCE APPROACHED AND COMBINED WITH THE
 MID-LEVEL REMNANT OF TROPICAL DEPRESSION TEN ON 20 AUGUST. BECAUSE
 IT IS IMPOSSIBLE TO DETERMINE WHICH OF THESE TWO SYSTEMS IS
 ASSOCIATED WITH TODAY'S GENESIS...WE HAVE ELECTED TO USE THE
 DESIGNATION TWELVE RATHER THAN TEN FOR THE NEW DEPRESSION. THIS
 SITUATION DIFFERS FROM LAST YEAR'S REGENERATION OF IVAN...IN WHICH
 THE LOW-LEVEL REMNANT OF THAT SYSTEM REMAINED A DISTINCT FEATURE
 THAT COULD BE FOLLOWED CONTINUOUSLY UNTIL IT REGENERATED.
 
 FORECASTER STEWART
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      23/2100Z 23.2N  75.5W    30 KT
  12HR VT     24/0600Z 24.0N  76.5W    35 KT
  24HR VT     24/1800Z 25.0N  77.7W    40 KT
  36HR VT     25/0600Z 25.7N  78.5W    45 KT
  48HR VT     25/1800Z 26.0N  79.4W    60 KT
  72HR VT     26/1800Z 26.3N  81.0W    50 KT...INLAND
  96HR VT     27/1800Z 26.5N  83.5W    60 KT
 120HR VT     28/1800Z 27.5N  86.0W    65 KT
  
  
 $$