WDPN31 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 29W (TWENTYNINE) 
WARNING NR 06//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 29W (TWENTYNINE), LOCATED APPROXIMATELY
150 NM SOUTH OF BANGK0K, THAILAND, HAS TRACKED NORTH-NORTHWESTWARD AT 
07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED 
SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED SHALLOW AND 
DISORGANIZED CONVECTION OBSCURING A WEAK LOW LEVEL CIRCULATION. THE 
INITIAL POSITION IS BASED ON A LOW REFLECTIVITY NOTCH FEATURE IN THE 
071121Z 37 GHZ SSMIS MICROWAVE PASS WITH POOR CONFIDENCE. THE INITIAL 
INTENSITY OF 25 KNOTS IS BASED ON THE PGTW DVORAK ESTIMATE OF T1.O. 
UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF LOW (05-10 
KNOT) VERTICAL WIND SHEAR (VWS) AND GOOD RADIAL OUTFLOW. SEA SURFACE 
TEMPERATURES ARE ALSO FAVORABLE AT 30 CELSIUS. HOWEVER, PROXIMITY TO 
THE MALAY PENINSULA IS CUTTING OFF MOISTURE INFLOW AND  INHIBITING 
FURTHER DEVELOPMENT. TD 29W IS TRACKING ALONG THE LOW-LEVEL 
SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE 
NORTHEAST.
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 29W WILL CONTINUE TO TRACK NORTHWESTWARD UNDER THE INFLUENCE 
OF THE STR THROUGHOUT THE FORECAST PERIOD. THE SYSTEM WILL WEAKEN TO 
20 KNOTS AS IT MAKES LANDFALL JUST SOUTH OF PRACHUAP KHIRI KHAN, 
THAILAND, NEAR TAU 06 AND CROSS THE MALAY PENINSULA. AFTER TAU 12, IT 
WILL EXIT INTO THE ANDAMAN SEA AND REGAIN TD STRENGTH AS OUTFLOW 
IMPROVES, PEAKING TO 30 KNOTS BY TAU 36. HOWEVER, JUST AFTER TAU 48, 
TD 29W WILL CROSS THE NORTHERN ANDAMAN ISLANDS AND BEGIN TO WEAKEN 
DUE LAND INTERACTION AND INCREASING VWS. BY TAU 72, TD 29W WILL 
DISSIPATE OVER THE BAY OF BENGAL. THERE IS A DISTINCT POSSIBILITY 
THAT 29W WILL NOT RECOVER AFTER IT TRACKS ACROSS THE RUGGED TERRAIN 
OF THE MALAY PENINSULA. AVAILABLE NUMERIC GUIDANCE IS IN GOOD 
AGREEMENT IN THE NEAR TERM, LEADING TO HIGH CONFIDENCE IN THE JTWC 
TRACK FORECAST UP TO TAU 24. AFTERWARD, THE MODEL ENVELOPE 
SIGNIFICANTLY SPREADS OUT AS THE CONSENSUS MEMBERS LOSE THE VORTEX -
AN INDICATION OF A VERY WEAK VORTEX. IN VIEW OF THIS, THERE IS LOW
CONFIDENCE IN THE LATTER PORTION OF THE JTWC TRACK FORECAST.//
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