178 
 WTNT43 KNHC 262034
 TCDAT3
 TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER   5
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL132007
 500 PM EDT WED SEP 26 2007
 
 THE CYCLONE'S CLOUD PATTERN IS WELL-ORGANIZED WITH DISTINCT BANDING
 FEATURES OVER THE SOUTHERN SEMICIRCLE AND A FAIRLY SYMMETRIC
 UPPER-LEVEL OUTFLOW.  SATELLITE-BASED INTENSITY ESTIMATES FROM TAFB
 AND SAB ARE BOTH AT TROPICAL STORM STRENGTH.  HOWEVER...LOOKS CAN
 BE DECEIVING...AND RECENT DATA FROM AN AIR FORCE HURRICANE HUNTER
 MISSION INDICATE THAT THE SYSTEM IS NOT YET A TROPICAL STORM.  THE
 ADVISORY INTENSITY REMAINS 30 KT...AND THIS MAY BE A GENEROUS
 ESTIMATE SINCE THE HIGHEST FLIGHT-LEVEL WINDS WERE ONLY 29 KT. 
 GIVEN THE ORGANIZATION OF THE SYSTEM...DECREASING SHEAR...AND VERY
 WARM WATERS...STRENGTHENING IS LIKELY.  THE OFFICIAL WIND SPEED
 FORECAST IS SIMILAR TO THE SHIPS GUIDANCE...AND COULD BE
 CONSERVATIVE.
 
 AIRCRAFT FIXES INDICATE THAT THE CYCLONE IS MEANDERING OR MAY BE
 EXECUTING A COUNTERCLOCKWISE LOOP.  THE TRACK FORECAST REASONING IS
 ABOUT THE SAME AS EARLIER TODAY.  A MID-TROPOSPHERIC RIDGE IS
 EXPECTED TO BUILD EASTWARD GRADUALLY FROM NORTHERN MEXICO INTO THE
 GULF OVER THE NEXT FEW DAYS.  THIS SHOULD EVENTUALLY STEER THE
 TROPICAL CYCLONE IN A GENERALLY WESTWARD DIRECTION TOWARD THE COAST
 OF MEXICO.  HOWEVER THE MODELS ARE NOT IN VERY GOOD AGREMMENT.  THE
 U.K. MET. OFFICE MODEL TRACK IS ON THE NORTH SIDE OF THE GUIDANCE
 SUITE WITH A WEST-NORTHWESTWARD MOTION ACROSS THE COAST IN ABOUT 66
 HOURS.  THE HWRF MODEL KEEPS THE SYSTEM MEANDERING OFFSHORE AND
 WEAKENS IT LATE IN THE FORECAST PERIOD.  THE GFDL MODEL SHOWS
 LANDFALL IN ABOUT 36 HOURS...IN CONTRAST TO THE MUCH SLOWER ECMWF
 WHICH DOES NOT SHOW THE CYCLONE CROSSING THE COASTLINE UNTIL NEARLY
 84 HOURS.  THE OFFICIAL FORECAST IS ABOUT IN THE MIDDLE OF THESE
 VARIOUS OBJECTIVE TRACKS.
 
 THE MEANDERING MOTION DELAYS THE ISSUANCE OF A TROPICAL STORM WATCH
 FOR THE GULF COAST OF MEXICO A LITTLE MORE...BUT THE WATCH COULD BE
 ISSUED LATER TONIGHT OR EARLY TOMORROW. 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      26/2100Z 21.3N  94.5W    30 KT
  12HR VT     27/0600Z 21.2N  94.8W    35 KT
  24HR VT     27/1800Z 20.9N  95.1W    45 KT
  36HR VT     28/0600Z 20.7N  95.6W    50 KT
  48HR VT     28/1800Z 20.5N  96.3W    55 KT
  72HR VT     29/1800Z 20.2N  97.8W    20 KT...INLAND
  96HR VT     30/1800Z...DISSIPATED
  
 $$
 FORECASTER PASCH