UNCLAS//N03144//
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (YANYAN) WARNING NR 
12//
RMKS/
WDPN31 PGTW 181500
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 181200Z2 TO 211200Z6 JAN 03.
   A. TROPICAL STORM (TS) 01W (YANYAN), LOCATED APPROXIMATELY 80 NM 
EAST OF ROTA, HAS TRACKED NORTHWARD AT 02 KNOTS OVER THE PAST 06 
HOURS. THE WARNING POSITION IS BASED ON RADAR IMAGERY AND AN 
181148Z3 SSM/I PASS. THE WARNING INTENSITY IS BASED ON SATELLITE 
CURRENT INTENSITY ESTIMATES OF 35 AND 45 KNOTS. RADAR IMAGERY AND 
THE LATEST SSM/I PASS INDICATE THAT THE LOW LEVEL CIRCULATION CENTER 
(LLCC) IS PARTIALLY EXPOSED AND THE DEEP CONVECTION IS IN THE 
WESTERN AND POLEWARD QUADRANTS.  
   B. TS 01W IS FORECAST TO TRACK SLOWLY NORTHWARD OVER THE NEXT 12 
TO 24 HOURS UNDER THE INFLUENCE OF A DEVELOPING LOW TO MID-LEVEL 
SUBTROPICAL RIDGE TO THE EAST-NORTHEAST OF THE SYSTEM. A MID-
LATITUDE SYSTEM LOCATED OVER THE SEA OF JAPAN IS EXPECTED TO DEEPEN 
AND PROPAGATE EASTWARD, WEAKENING THE LOW TO MID LEVEL RIDGE BY 36 
HOURS. TS 01W IS EXPECTED TO TRACK NORTHEASTWARD AFTER 24 HOURS INTO 
THE DEVELOPING WEAKNESS. THE AVAILABLE DYNAMIC AIDS CONSISTING OF 
NOGAPS, GFDN, THE JAPANESE GLOBAL SPECTRAL (JGSM) AND TYPHOON (JTYM) 
MODELS, UKMET GLOBAL SPECTRAL MODEL (EGRR), NCEP AVIATION (AVN), 
COAMPS, AND AFWA MM5, ARE IN FAIR AGREEMENT. GFDN MAINTAINS THE 
VERTICAL STACKING AND THE STRONGEST DEVELOPMENT OF THE LOW MOVING 
OFF OF JAPAN RESULTING IN A FASTER SPEED OF MOVEMENT TO THE 
NORTHEAST.  AVN ON THE OTHER HAND, DECOUPLES THE SYSTEM AND HAS THE 
LLCC MOVING SLOWLY TO THE EAST. THE REMAINING AIDS AGREE IN SLOW 
MOVEMENT POLEWARD OVER THE NEXT 24 HOURS AND THEN INCREASING 
MOVEMENT TO THE NORTHEAST. OUR FORECAST IS BASED ON PERSISTENCE AND 
A BLEND OF THE AVAILABLE DYNAMIC AIDS.
   C. TS 01W IS EXPECTED TO WEAKEN AS IT TRACKS POLEWARD NORTH OF 
THE UPPER LEVEL RIDGE AXIS INTO INCREASING VERTICAL SHEAR. 
   D. INITIAL AND FORECAST WIND RADII ARE BASED ON SYNOPTIC 
OBSERVATIONS AND CLIMATOLOGY FOR AN AVERAGE SIZED SYSTEM.
FORECAST TEAM: LEEJOICE/HEATH/EDBERG//