WDPN31 PGTW 210300 
MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (FAXAI) WARNING NR 38//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 210000Z3 TO 240000Z6 DEC 01.
   A. TYPHOON (TY) 31W (FAXAI) IS LOCATED ABOUT 110 NM NORTH OF 
POHNPEI AND HAS TRACKED WEST-NORTHWESTWARD AT 08 KNOTS DURING THE 
PAST 6 HOURS. THE WARNING POSITION IS BASED ON 202330Z0 VISIBLE AND
INFRARED SATELLITE IMAGERY. TYPHOON 31W (FAXAI) HAS CONTINUED TO 
BECOME BETTER ORGANIZED WITH IMPROVING BANDING FEATURES AND THE 
APPEARANCE OF A SMALL RAGGED EYE IN VISIBLE SATELLITE IMAGERY. TY 
31W (FAXAI) HAS CONTINUED TO RAPIDLY INTENSIFY DURING THE PAST 12 
HOURS. THE WARNING INTENSITY OF 75 KT IS BASED ON DVORAK SATELLITE 
INTENSITY ESTIMATES OF 77 KT (T4.5) FROM JTWC AND 90 KT (T5.0) FROM 
AFWA. THE INTENSITY WAS HELD DOWN SLIGHTLY SINCE IT WILL TAKE SOME 
TIME FOR THE WIND FIELD TO CATCH UP WITH THE RAPIDLY CHANGING 
CONVECTIVE PATTERN. 
   B. TY 31W HAS BEEN TRACKING STEADILY WEST-NORTHWESTWARD NOW FOR 
THE PAST 24 HOURS OR SO. THE STRONG SUBTROPICAL RIDGE TO THE NORTH 
OF THE CYCLONE IS EXPECTED TO CHANGE LITTLE DURING THE FORECAST 
PERIOD, WHICH SHOULD KEEP TY 31W MOVING IN THE GENERAL DIRECTION OF 
THE MARIANA ISLANDS. ALL OF THE GLOBAL MODELS AND OTHER DYNAMICAL 
MODELS ARE TIGHTLY CLUSTERED AROUND THE PREVIOUS FOUR JTWC FORECAST 
TRACKS, EXCEPT FOR THE AVN MODEL WHICH IS WELL NORTH OF THE MODEL 
SUITE. THE AVN IS CONSIDERED BE AN OUTLIER SINCE IT APPEARS TO BREAK 
DOWN THE SUBTROPICAL RIDGE TOO QUICKLY AND, THEREFORE, WAS NOT 
CONSIDERED IN THIS FORECAST SCENARIO. 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 JUST AN EXTENSION OF THE PREVIOUS FORECAST AND 
LIES BETWEEN THE JGSM-JTYM MODELS TO THE NORTH AND THE GFDN-NOGAPS-
UKMET MODELS TO THE SOUTH.
   C. THE INTENSITY FORECAST IS NOT AS STRAIGHT-FORWARD AS THE TRACK 
FORECAST IS. SATELLITE INTENSITY ESTIMATES INDICATE THAT TY 31W HAS 
BEEN RAPIDLY INTENSIFYING FOR ABOUT THE PAST 12 HOURS OR SO. AS 
SUCH, RAPID INTENSIFICATION IS EXPECTED TO CONTINUE FOR ANOTHER 12 
TO 18 HOURS. AFTERWARDS, A GRADUAL LEVELING OFF IN THE INTENSITY IS 
EXPECTED AS THE WIND AND MASS FIELDS TRY TO COME INTO BALANCE. BY 48 
HOURS, ANOTHER PERIOD OF RAPID INTENSIFICATION IS POSSIBLE AS THE 
CYCLONE MOVES INTO A VERY FAVORABLE UPPER-LEVEL OUTFLOW PATTERN 
CREATED BY THE STRONG POLAR JET TO THE NORTH OF 20N LATITUDE AND 
DECREASING SHEAR UNDER THE 200 MB RIDGE AXIS. GIVEN THE VERY 
FAVORABLE UPPER-LEVEL FLOW PATTERN EXPECTED LATE IN THE FORECAST 
PERIOD, IT IS NOT OUT OF THE QUESTION THAT TY 31W COULD BECOME A 
SUPER TYPHOON (130 KT) AS IT MOVES THROUGH THE SOUTHERN MARIANA 
ISLANDS BY 72 HOURS.
   D. CURRENT WIND RADII ARE BASED ON RECENT QUIKSCAT AND SSMI GALE 
WIND ANALYSES, AND SYNOPTIC DATA FROM THE CAROLINE ISLANDS. FORECAST 
WIND RADII ARE BASED ON CLIMATOLOGY FOR A SMALLER THAN AVERAGE SIZE 
TROPICAL CYCLONE. 
FORECAST TEAM: STEWART/LEEJOICE/JACOBS/LAM//