MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (NANGKA) WARNING NR 47// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 11W (NANGKA), LOCATED APPROXIMATELY 518 NM SOUTH- SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED NORTHWARD AT 10 KNOTS OVER THE PAST SIX HOURS. RECENT ANIMATED MSI DEPICTS A 13 NM DIAMETER EYE THAT SUPPORTS THE HIGH CONFIDENCE IN THE CURRENT POSITION. THE INITIAL INTENSITY REMAINS AT 90 KNOTS BASED ON AN OVERALL ASSESSMENT OF DVORAK INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES. TY NANGKA IS LOCATED IN AN AREA OF LOW VWS AND EXCELLENT EQUATORWARD OUTFLOW. HOWEVER, THERE IS STILL SOME DRY AIR ON THE WESTERN EDGE INHIBITING THE DEVELOPMENT. TY 11W IS TRACKING ALONG THE WESTERN PERIPHERY OF THE DEEP LAYERED SUB-TROPICAL RIDGE (STR) TO THE EAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 11W WILL CONTINUE TO TRACK POLEWARD ALONG THE WESTERN PERIPHERY OF THE STEERING STR IN THE SHORT TERM. AFTERWARD, THIS STR IS EXPECTED TO REBUILD, FORCING TY NANGKA ON A WEST-NORTHWESTWARD TRAJECTORY. THE TUTT LOCATED TO THE NORTHEAST WILL WEAKEN AND TRACK FURTHER NORTHWARD, SLIGHTLY IMPROVING THE UPPER-LEVEL CONDITIONS. ALSO, ENVIRONMENTAL CONDITIONS WILL REMAIN, ALLOWING MODEST INTENSIFICATION OVER THE NEXT 24 HOURS. AS THE SYSTEM GAINS LATITUDE, DEGRADED CONDITIONS WILL BEGIN TO WEAKEN THE CYCLONE AS IT APPROACHES AND MAKES LANDFALL OVER THE SOUTHERN COAST OF SHIKOKU. C. IN THE EXTENDED TAUS, TY NANGKA WILL TRACK NORTHEASTWARD ALONG THE THE NORTHWESTERN EDGE OF THE STR. THE COMBINED EFFECTS OF SIGNIFICANT INCREASING VWS AND COOLER SSTS WILL FURTHER WEAKEN THE SYSTEM, LEADING TO ITS DISSIPATION BY THE END OF THE FORECAST PERIOD. AVAILABLE MODEL GUIDANCE IS OVERALL IN FAIR AGREEMENT; HOWEVER, DUE TO THE CONTINUED SPREAD AND UNCERTAINTY IN THE EXTENT OF THE STR, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN