WDPN31 PGTW 160300 MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W /WARNING NR 15// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 160000Z7 TO 210000Z3 OCT 2004. A. TYPHOON (TY) 27W (TOKAGE), LOCATED APPROXIMATELY 695 NM SOUTH-SOUTHEAST OF OKINAWA, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 05 KNOTS OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED ON 152330Z4 MULTISPECTRAL SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 90 AND 102 KNOTS. RECENT MULTISPECTRAL SATELLITE IMAGERY REVEALS A SMALL EYE, AND THE STRONGEST CONVECTION REMAINS IN THE SOUTHWEST QUADRANT. B. DURING THE NEXT 24 HOURS, TY 27W (TOKAGE) IS FORECAST TO TRACK NORTHWESTWARD AS A MAJOR SHORTWAVE TROUGH (MSWT) OVER JAPAN SLIGHTLY WEAKENS THE SUBTROPICAL STEERING RIDGE ANCHORED TO THE NORTHEAST. BETWEEN TAU 24 AND TAU 72, THE SYSTEM SHOULD TRACK MORE WESTWARD AS THE RIDGE REBUILDS AND THE AXIS REORIENTS AFTER TROUGH PASSAGE. BY TAU 72, A SECONDARY MSWT WILL MOVE OFF OF THE EAST COAST OF CHINA AND WEAKEN THE RIDGE AXIS. THIS WEAKENING SHOULD BE SIGNIFICANT ENOUGH TO ALLOW TY 27W TO TURN POLEWARD AND BEGIN TRACKING INTO THE EAST CHINA SEA. THE AVAILABLE DYNAMIC AIDS CONSISTING OF COAMPS, UKMO, TCLAPS, JGSM, JTYM, NOGAPS, GFDN, WBAR, AND MM5 ARE IN POOR AGREEMENT. MM5 AND WBAR RESOLVE SOLUTIONS WHICH TRACK TY 27W ALMOST IMMEDIATELY POLEWARD WHILE COAMPS AND TCLAPS RESOLVE SOLUTIONS WHICH MAINTAIN AN ALMOST DUE WEST TRACK. THE REMAINDER OF THE AIDS SHOW A GENERAL PROGRESSION TO THE NORTHWEST WITH UKMO BEING THE MOST WESTWARD OUTLIER. THIS FORECAST IS BASED ON A CONSENSUS OF ALL DYNAMIC AIDS WITH LESS EMPHASIS ON MM5, WBAR, COAMPS, AND TCLAPS. GIVEN THE POOR AGREEMENT IN THE DYNAMIC AIDS, AN ALTERNATE SCENARIO IS POSSIBLE. THIS SCENARIO CALLS FOR A STRENGTHENING OF THE RIDGE OVER CHINA WHICH WOULD PREVENT THE SYSTEM FROM TURNING POLEWARD. C. THE INTENSITY OF TY 27W IS FORECAST TO SLOWLY STRENGTHEN DURING THE NEXT 48 HOURS, AND IT IS EXPECTED TO REACH PEAK INTENSITY AT APPROXIMATELY TAU 36. RECENT ANIMATED WATER VAPOR IMAGERY REVEALS A CONSISTENT EQUATORWARD OUTFLOW CHANNEL AND AN ELONGATED POLEWARD OUTFLOW CHANNEL, HOWEVER THE POLEWARD CHANNEL HAS WEAKENED SLIGHTLY DURING THE PAST SEVERAL HOURS. ADDITIONALLY, A LARGE REGION OF DRY AIR IS SITUATED OVER THE EAST CHINA SEA. DUE TO INCREASED DRY AIR ENTRAINMENT AFTER TAU 48, THE SYSTEM IS EXPECTED TO START WEAKENING. D. CURRENT WIND RADII ARE BASED ON A 151622Z7 AMSR-E MICROWAVE PASS. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR A LARGE SIZED SYSTEM. E. TY 27W IS FORECAST TO TRACK MORE POLEWARD DURING THE EXTENDED TAUS AS THE MSWT WEAKENS THE RIDGE AXIS. ADDITIONALLY, INCREASED DRY AIR AND PASSAGE OVER COOLER SEA SURFACE TEMPERATURES AT THIS TIME WILL WEAKEN THE SYSTEM. GIVEN THE LARGE VARIANCE IN THE DYNAMIC AIDS, CONFIDENCE IN THE EXTENDED FORECAST IS LOW. FURTHERMORE, AN ALTERNATE SCENARIO EXISTS WHICH MAINTAINS THE RIDGE STRENGTH AND KEEPS THE SYSTEM FROM TURNING POLEWARD. FORECAST TEAM: LEFFLER/CHRISTIAN/LEWIN// NNNN