WDPN31 PGTW 171500 
MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 31W (FAXAI) WARNING NR 
24//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 171200Z1 TO 201200Z5 DEC 01.
   A. TROPICAL STORM (TS) 31W (FAXAI), LOCATED APPROXIMATELY 180 NM 
EAST-SOUTHEAST OF THE ISLAND OF POHNPEI, HAS DRIFTED WEST-
NORTHWESTWARD AT 2 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION 
IS BASED ON 171130Z3 INFRARED SATELLITE IMAGERY, RECENT MICROWAVE 
SATELLITE IMAGERY, AND SYNOPTIC DATA. THE WARNING INTENSITY IS BASED 
ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS. 
ANIMATED INFRARED SATELLITE IMAGERY INDICATES THAT THE DEEP 
CONVECTION HAS BECOME MORE PERSISTENT OVER THE LOW LEVEL CIRCULATION 
CENTER (LLCC). A 170924Z3 SPECIAL SENSOR MICROWAVE IMAGE (SSM/I) 
PASS SHOWS THAT THE SYSTEM HAS BECOME MORE ORGANIZED AND 
CONSOLIDATED AROUND THE LLCC OVER THE PAST 12 HOURS. 
   B. TS 31W REMAINS EMBEDDED IN A WEAK STEERING ENVIRONMENT WITHIN 
THE HORIZONTAL SHEAR OF THE SUBTROPICAL NORTHEASTERLIES AND 
EQUATORIAL WESTERLIES. THE SYSTEM IS EXPECTED TO REMAIN IN THIS 
ENVIRONMENT, THEREFORE, IT SHOULD CONTINUE TO TRACK IN A GENERAL 
WEST-NORTHWESTWARD DIRECTION WITH SHORT TERM FLUCTUATIONS. THE 
AVAILABLE MODELS OF AVN, GFDN, NOGAPS, JTYM, AND THE UKMET (EGRR) 
ARE IN FAIR AGREEMENT, TRACKING THE SYSTEM WEST-NORTHWESTWARD. THE 
MODELS VARY SLIGHTLY IN SPEED OF MOTION AND DIRECTION. GFDN AND NGPS 
TRACK THE SYSTEM RAPIDLY WEST-NORTHWESTWARD, WHILE AVN AND JTYM 
INDICATE A MORE NORTHWARD MOVEMENT INTO A WEAKNESS OF THE MID LEVEL 
SUBTROPICAL RIDGE. EGRR IS MORE SOUTH, DEPICTING A WEAKENING TREND 
AND SLOW TRACK. OUR FORECAST IS BASED ON PERSISTENCE AND A BLEND OF 
THE AFOREMENTIONED MODELS.
   C. 200 MB ANALYSIS INDICATES TS 31W IS IN A WEAK VERTICAL WIND 
SHEAR ENVIRONMENT WITH FAIR OUTFLOW ALOFT. CONDITIONS SHOULD REMAIN 
THE SAME AS THE SYSTEM TRACKS SOUTH OF THE UPPER LEVEL RIDGE AXIS. 
THEREFORE, TS 31W IS EXPECTED TO SLOWLY INTENSIFY THROUGH THE 
PERIOD.  
   D. WIND RADII ARE BASED ON A RECENT QUIKSCAT PASS AND CLIMATOLOGY 
FOR AN AVERAGED SIZE SYSTEM. 
FORECAST TEAM: VILPORS/WAUGAMAN/NUTONGLA//



NNNN