MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 31W (YUTU) WARNING NR 28// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 31W (YUTU), LOCATED APPROXIMATELY 501 NM EAST- NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 45-NM RAGGED EYE IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) WHICH ALSO SHOWS THE DEEP CONVECTION HAS ERODED ON THE EASTERN SIDE OF THE CYCLONE. THE INITIAL INTENSITY OF 130 KNOTS FOLLOWS MULTI-AGENCY DVORAK ESTIMATES OF T6.5-T7.0 (127- 140 KNOTS). THE ENVIRONMENT IS MARGINALLY FAVORABLE WITH LOW (10-15 KNOT) VERTICAL WIND SHEAR (VWS), GOOD RADIAL OUTFLOW, AND WARM SEA SURFACE TEMPERATURE (28-29 CELSIUS) BEING OFFSET BY DRY AIR FROM THE WEST WRAPPING AROUND TO THE EASTERN PERIPHERY OF THE CYCLONE. STY 31W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. STY 31W WILL CONTINUE TO TRACK WESTWARD TO WEST-SOUTHWESTWARD TOWARD LUZON, MAKE LANDFALL SHORTLY AFTER TAU 36 AND RE-EMERGE INTO THE SOUTH CHINA SEA (SCS) AFTER TAU 48. THE SYSTEM IS EXPECTED TO WEAKEN TO 115 KNOTS PRIOR TO LANDFALL AS DRY AIR CONTINUES TO IMPACT THE CYCLONE, WEAKEN SIGNIFICANTLY OVER LUZON, AND RE-INTENSIFY SLIGHTLY IN THE SCS. THE INTENSITY FORECAST CLOSELY FOLLOWS THE HWRF INTENSITY FORECAST, WHICH HAS A TRACK VERY SIMILAR TO THE JTWC FORECAST TRACK. THE JTWC TRACK FORECAST IS CLOSE TO THE CONSENSUS TRACK. WITH SPREAD IN THE MODELS OF ABOUT 150 NM AT TAU 72, UNCERTAINTY IN THE JTWC TRACK FORECAST IS LOW FOR THIS PORTION OF THE FORECAST. C. BEYOND TAU 72, AN APPROACHING MID-LATITUDE TROUGH WILL WEAKEN THE STR AND ALLOW STY 31W TO RECURVE NORTHWARD. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE MARGINALLY FAVORABLE WITH STRONG RADIAL OUTFLOW BEING OFFSET BY HIGH VWS AND THE ENTRAINMENT OF COOL, DRY AIR. EVERY NUMERICAL MODEL MEMBER IN THE CONSENSUS PREDICTS RECURVATURE BUT, BY TAU 120, THE SPREAD IS ABOUT 400 NM DUE TO DIFFERENCES IN THE TIMING AND DEGREE OF RECURVATURE. BASED ON THIS SPREAD, UNCERTAINTY IS LOW IN THE EXTENDED PORTION OF THE JTWC TRACK FORECAST.// NNNN NNNN