WDPN31 PGTW 211500 
MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (FAXAI) WARNING NR 40//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 211200Z6 TO 241200Z9 DEC 01.
   A. TYPHOON (TY) 31W (FAXAI), LOCATED APPROXIMATELY 345 NM 
EAST-NORTHEAST OF CHUUK, HAS TRACKED NORTHWESTWARD AT 10 KNOTS 
DURING THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 211130Z8 
INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON 
SATELLITE CURRENT INTENSITY ESTIMATES OF 102 AND 115 KNOTS. A 
211012Z7 SPECIAL SENSOR MICROWAVE IMAGE (SSM/I) PASS AND ANIMATED 
INFRARED SATELLITE IMAGERY REVEAL THAT THE SYSTEM HAS A SMALL EYE 
WITH A DIAMETER OF APPROXIMATELY 14 NM, AND HAS RAPIDLY INTENSIFIED 
OVER THE PAST 12 HOURS. ANIMATED WATER VAPOR IMAGERY INDICATES THAT 
THE UPPER LEVEL RIDGE NORTH OF THE SYSTEM HAS WEAKENED SLIGHTLY, 
RESULTING IN A POLEWARD OUTFLOW CHANNEL FAVORABLE FOR DEVELOPMENT.
   B. TY 31W HAS BEEN TRACKING NORTHWESTWARD DURING THE PAST 6 
HOURS, BUT IS EXPECTED TO BEGIN TRACKING MORE WEST-NORTHWESTWARD 
OVER THE NEXT 12 HOURS. THE MID-LEVEL SUBTROPICAL RIDGE NORTH OF THE 
SYSTEM IS EXPECTED TO MAINTAIN ITS STRENGTH FOR THE NEXT 48 TO 72 
HOURS. AS A RESULT, TY 31W SHOULD TRACK WEST-NORTHWESTWARD THROUGH 
THE REST OF THE FORECAST PERIOD. THE AVAILABLE DYNAMIC AIDS 
CONSISTING OF GEOPHYSICAL FLUID DYNAMICS NAVY (GFDN), NOGAPS (NGPS), 
NCEP AVIATION (AVN), UK MET OFFICE (EGRR), JMA TYPHOON (JTYM) AND 
GLOBAL SPECTRAL (JGSM) MODELS ARE IN GOOD AGREEMENT WITH THIS 
SCENARIO, EXCEPT FOR AVN. AVN IS CONSIDERED AN OUTLIER SINCE IT 
APPEARS TO BREAK DOWN THE SUBTROPICAL RIDGE TOO QUICKLY AND, 
THEREFORE, WAS NOT CONSIDERED IN THIS FORECAST. TOWARD THE END OF 
THE FORECAST PERIOD, THE OTHER MODELS GRADUALLY ERODE THE WESTERN 
PORTION OF THE SUBTROPICAL RIDGE ACROSS OR JUST WEST OF THE MARIANA 
ISLANDS. THE AMOUNT OF ACTUAL RIDGE EROSION THAT OCCURS WILL 
DETERMINE WHETHER OR NOT TY 31W PASSES OVER OR WELL TO THE NORTH OF 
GUAM. THE CURRENT FORECAST TRACK IS AN EXTENSION OF THE PREVIOUS 
FORECAST AND LIES BETWEEN THE JGSM-EGRR MODELS TO THE NORTH AND THE 
GFDN-NOGAPS-JTYM MODELS TO THE SOUTH.
   C. SATELLITE INTENSITY ESTIMATES INDICATE THAT TY 31W HAS 
RAPIDLY INTENSIFIED DURING THE PAST 12 HOURS. INTENSIFICATION IS 
EXPECTED TO CONTINUE FOR ANOTHER 18 TO 36 HOURS AS THE CYCLONE MOVES 
UNDER A VERY FAVORABLE UPPER-LEVEL OUTFLOW PATTERN. 
   D. CURRENT WIND RADII ARE BASED ON RECENT QUIKSCAT AND SSMI GALE 
WIND ANALYSES. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR A 
SMALLER THAN AVERAGE SIZE TROPICAL CYCLONE. 
FORECAST TEAM: VILPORS/WAUGAMAN/NUTONGLA//



NNNN