UNCLAS//N03144// MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (YANYAN) WARNING NR 14// RMKS/ WDPN31 PGTW 190300 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 190000Z0 TO 220000Z4 JAN 03. A. TROPICAL STORM (TS) 01W (YANYAN), LOCATED APPROXIMATELY 140 NM EAST-SOUTHEAST OF SAIPAN, HAS TRACKED EASTWARD AT 07 KNOTS OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED ON 182330Z7 VISIBLE AND INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 45 AND 55 KNOTS AND A 182223Z8 QUIKSCAT PASS DEPICTING 50 KNOT WINDS NEAR THE CIRCULATION CENTER. A 182229Z4 SSM/I PASS DEPICTS DRY AIR ALONG THE WESTERN QUADRANT. B. TS 01W IS FORECAST TO TRACK NORTHEASTWARD THROUGH THE PERIOD UNDER THE INFLUENCE OF A LOW TO MID-LEVEL SUBTROPICAL RIDGE TO THE EAST. A MID-LATITUDE SYSTEM LOCATED OVER SOUTHERN JAPAN IS EXPECTED TO DEEPEN AND PROPAGATE EASTWARD. TS 01W IS FORECAST TO INTERACT WITH THE SYSTEM BY THE END OF THE PERIOD AND BEGIN TRANSITIONING INTO AN EXTRATROPICAL SYSTEM BY 48 TO 72 HOURS. 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 THROUGH 48 HOURS. AVN, EGRR, AND JGSM WEAKEN THE SYSTEM AFTER 48 HOURS. GFDN, NOGAPS, JTYM, COAMPS, AND AFWA INTERACT TS 01W WITH THE APPROACHING SYSTEM MORE AGGRESSIVELY, RESULTING IN A FASTER TRACK. OUR FORECAST IS BASED ON PERSISTENCE AND A BLEND OF THE AVAILABLE DYNAMIC AIDS. C. TS 01W IS EXPECTED TO WEAKEN AS IT TRACKS NORTH OF THE UPPER LEVEL RIDGE AXIS INTO INCREASING VERTICAL SHEAR. D. INITIAL AND FORECAST WIND RADII ARE BASED ON A 182223Z8 QUIKSCAT PASS AND CLIMATOLOGY FOR AN AVERAGE SIZED SYSTEM. FORECAST TEAM: WINGEART/GRUBER/LAM/STATEN/KUMAGA// NNNN