WDPN31 PGTW 190300 MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W WARNING NR 21// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 190000Z0 TO 240000Z6 NOV 2004. A. TYPHOON (TY) 29W (MUIFA), LOCATED APPROXIMATELY 200 NM EAST- NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED SOUTHWESTWARD AT 01 KNOT OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED ON 182330Z7 MULTISPECTRAL SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 90, 102, AND 115 KNOTS. RECENT ANIMATED ENHANCED WATER VAPOR IMAGERY REVEALS THE POLE- WARD OUTFLOW CHANNEL HAS BEEN SIGNIFICANTLY DIMINISHED, AND AN 182248Z5 SSMI MICROWAVE PASS SHOWS A TIGHTLY CURVED EYE. B. DURING THE NEXT 12 TO 24 HOURS, TY 29W IS FORECAST TO BEGIN TRACKING SOUTHWESTWARD UNDER THE INFLUENCE OF THE SUBTROPICAL STEER- ING RIDGE LOCATED OVER SOUTHEAST ASIA. THE MAJOR SHORTWAVE TROUGH WHICH IS CURRENTLY SITUATED OVER THE RYUKYU ISLANDS HAS WEAKENED THE RIDGE TO THE EAST OF TY 29W, AND THE ENVIRONMENT SUPPORTING THE QUASI-STATIONARY FLOW IS RESPONDING TO THE CHANGE IN RIDGE STRENGTH. AFTER TAU 24 TO TAU 36, THE SYSTEM SHOULD REMAIN ON A GENERAL SOUTH- WESTWARD TRACK AS NO SIGNFICIANT CHANGE TO THE STEERING RIDGE IS ANTICIPATED. THE AVAILABLE DYNAMIC AIDS CONSISTING OF AVN, UKMO, COAMPS, MM5, WBAR, JTYM, JGSM, GFDN, AND NOGAPS ARE IN GOOD AGREE- MENT. WBAR AND JTYM DEPICT A SLIGHTLY POLEWARD SOLUTION WHILE MM5 AND COAMPS ARE MORE EQUATORWARD. THIS FORECAST IS BASED ON A CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS WITH LESS EMPHASIS ON WBAR AND JTYM. C. TY 29W IS IN AN ENVIRONMENT BOUNDED TO THE NORTHWEST BY MODER- ATE TO HIGH VERTICAL WIND SHEAR. THIS SHEAR HAS WEAKENED THE POLEWARD OUTFLOW CHANNEL AND CONSEQUENTLY, THE EYEWALL STRUCTURE HAS BROKEN DOWN. DURING THE NEXT 24 HOURS, THE INTENSITY OF TY 29W WILL CONTINUE TO DECREASE AS THE SYSTEM MOVES OVER THE PHILIPPINES. AS THE SYSTEM ENTERS THE SOUTH CHINA SEA, IT IS EXPECTED TO SLIGHTLY REGAIN STRENGTH, HOWEVER THE INTENSIFICATION SHOULD BE MINIMAL. D. CURRENT WIND RADII ARE BASED ON CONTINUITY FROM THE PREVIOUS FORECAST AND ON A 181808Z6 AMSU-B MICROWAVE PASS. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE SIZED SYSTEM. E. DURING THE EXTENDED TAUS, TY 29W IS FORECAST TO TRACK WESTWARD INTO VIETNAM. LANDFALL IS EXPECTED BETWEEN TAU 96 AND TAU 120. THE INTENSITY OF THE SYSTEM WILL QUICKLY WEAKEN ONCE THE SURFACE INFLOW IS DISRUPTED AND DRY AIR ENTRAINMENT BEGINS. 3. FORECAST TEAM: LEFFLER/CHRISTIAN/LEWIN//