000
WTNT41 KNHC 290242
TCDAT1
TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL162010
1100 PM EDT TUE SEP 28 2010

TROPICAL DEPRESSION SIXTEEN CONTINUES TO HAVE A STRUCTURE MORE
CHARACTERISTIC OF A WESTERN NORTH PACIFIC/NORTH INDIAN OCEAN
MONSOON DEPRESSION.  SURFACE OBSERVATIONS CONTINUE TO INDICATE
WINDS OF 20 KT OR LESS OVER AN AREA ENCOMPASSING 100 N MI IN
DIAMETER FROM THE CENTER...AND THAT THE STRONGEST WINDS AND
CONVECTION ARE 250-300 N MI AWAY FROM THE CENTER IN THE
SOUTHEASTERN QUADRANT.  AN EARLIER AIR FORCE RESERVE HURRICANE
HUNTER MISSION IN THIS AREA FOUND FLIGHT-LEVEL WINDS SUPPORTING AN
INITIAL INTENSITY OF 30 KT.  SURFACE OBSERVATIONS INDICATE THAT THE
CENTRAL PRESSURE IS NEAR 997 MB.

THERE ARE MULTIPLE LOW-LEVEL CLOUD SWIRLS PRESENT...AND THE CENTER
APPEARS TO RE-FORM FROM TIME TO TIME.  THE INITIAL MOTION OF 035/7
IS THUS A BIT UNCERTAIN.  OTHER THAN THAT...THERE IS NO CHANGE IN
THE FORECAST PHILOSOPHY FROM THE PREVIOUS ADVISORY...AND ONLY MINOR
CHANGES TO THE FORECAST TRACK.  A COMBINATION OF A DEEP-LAYER
TROUGH OVER THE SOUTHEASTERN UNITED STATES AND EASTERN GULF OF
MEXICO AND A LOW/MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC SHOULD
STEER THE CYCLONE NORTH-NORTHEASTWARD WITH ACCELERATION FOR THE
NEXT 12-24 HOURS...FOLLOWED BY A QUICK NORTHWARD MOTION.  THERE IS
SOME SPREAD IN BOTH THE SPEED AND DIRECTION OF MOTION BY 48 HR. 
THE GFS... GFDL...AND HWRF ARE MUCH FASTER AND TO THE LEFT OF THE
REST OF THE GUIDANCE...WHILE THE NOGAPS...GFDN...AND GFS ENSEMBLE
MEAN ARE SLOWER AND TO THE RIGHT.  THESE DIFFERENCES LIKELY RESULT
FROM THE MODEL HANDLING OF THE DEPRESSION INTERACTING WITH A
DEVELOPING BAROCLINIC LOW OVER THE EASTERN UNITED STATES.  THE NEW
FORECAST TRACK IS DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE CLOSE TO
THE CONSENSUS MODELS.

THE DEPRESSION IS CURRENTLY IN AN ENVIRONMENT OF 15 KT OF
SOUTHWESTERLY VERTICAL WIND SHEAR...WHICH THE LARGE-SCALE MODELS
FORECAST TO INCREASE DURING THE NEXT 12-24 HR.  THUS...NEITHER THE
ENVIRONMENT NOR THE CURRENT STRUCTURE ARE CONDUCIVE FOR SIGNIFICANT
STRENGTHENING.  THE INTENSITY FORECAST IS THE SAME AS IN THE
PREVIOUS ADVISORY...WITH MODEST STRENGTHENING ALONG THE LINES OF
THE SHIPS AND LGEM MODELS.  EXTRATROPICAL TRANSITION IS EXPECTED TO
BEGIN IN ABOUT 24 HR OR SO AND BE COMPLETE BY 36-48 HR.  THE
CYCLONE IS FORECAST TO BE ABSORBED BY THE EASTERN U. S. BAROCLINIC
LOW AFTER 48 HR...AS FORECAST BY MOST OF THE DYNAMICAL GUIDANCE.
 
UNLESS THE STRUCTURE CHANGES RADICALLY IN THE NEXT 12-24 HOURS...IT
IS LIKELY THAT THERE WILL CONTINUE TO BE A LARGE AREA OF LIGHT
WINDS NEAR THE CENTER.  THE STRONGEST WINDS SHOULD OCCUR IN AREAS
WELL TO THE EAST OF THE FORECAST TRACK.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/0300Z 21.9N  81.9W    30 KT
 12HR VT     29/1200Z 23.3N  81.2W    35 KT
 24HR VT     30/0000Z 26.3N  80.2W    40 KT
 36HR VT     30/1200Z 30.6N  79.3W    40 KT...POST-TROP/EXTRATROP
 48HR VT     01/0000Z 36.3N  78.0W    35 KT...POST-TROP/EXTRATROP
 72HR VT     02/0000Z...ABSORBED BY EXTRATROPICAL LOW
 
$$
FORECASTER BEVEN