MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (LINGLING) WARNING NR 021// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 15W (LINGLING), LOCATED APPROXIMATELY 117 NM SOUTHWEST OF OSAN AB, HAS TRACKED NORTHWARD AT 27 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THAT TY 15W REMAINS A RAPIDLY DECAYING SYSTEM. THE PREVIOUS EYE FEATURE HAS FILLED WITH CONVECTION, THUS THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON A SMALL DIMPLE IN THE CENTER OF THE CIRCULATION AS EVIDENT IN THE 070000Z HIMAWARI-8 VISIBLE 1KM IMAGERY AND SUPPORTED BY CURRENT COMPOSITE RADAR DATA. THE INITIAL INTENSITY IS ASSESSED AT 75 KTS BASED MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T4.5/77KTS FROM PGTW AND RJTD. THESE ESTIMATES ARE SLIGHTLY HIGHER THAN THE ADVANCED DVORAK TECHNIQUE ESTIMATE OF T4.3/67KTS FROM CIMSS, WHICH IS REFLECTED IN THE DECREASE IN INTENSITY. UPPER-LEVEL ANALYSIS REVEALS THAT TY 15W IS TRACKING THROUGH AN UNFAVORABLE ENVIRONMENT WITH STRONG (25-30 KTS) VERTICAL WIND SHEAR (VWS) AND COOL (25-26 CELSIUS) SEA SURFACE TEMPERATURE (SST) BEING OFFSET SOMEWHAT BY STRONG POLEWARD OUTFLOW. AS THE MOTION OF THE SYSTEM IS IN-PHASE WITH THE VWS, RELATIVE SHEAR AFFECTING THE SYSTEM IS LOW, ALLOWING THE STORM TO DECAY AT A SLOWER RATE. TY 15W REMAINS TRACKING NORTHWARD ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) AND WILL TURN TO A MORE NORTH-NORTHEAST TRACK PRIOR TO TAU 12. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 15W WILL MAKE LANDFALL OVER RUGGED TERRAIN PRIOR TO TAU 12 ALONG THE SOUTHWEST COAST OF NORTH KOREA, CONTINUING ON A NORTH- NORTHEAST TRACK THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. CONCURRENTLY, IT WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS THE SYSTEM ACCELERATES WITH MIDLATITUDE WESTERLIES. DUE TO INCREASING VWS VALUES AND LAND INTERACTION, TY 15W WILL RAPIDLY DECAY AS IT TRANSITS ACROSS THE KOREAN PENINSULA. BY TAU 24, THE SYSTEM IS FORECAST TO COMPLETE ETT. THROUGHOUT THE FORECAST, NUMERICAL MODELS ARE IN TIGHT AGREEMENT, PLACING HIGH CONFIDENCE IN THE ENTIRE JTWC TRACK FORECAST.// NNNN NNNN