MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (KHANUN) WARNING NR 11// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 08W (KHANUN), LOCATED APPROXIMATELY 205 NM SOUTH OF CHEJU-DO, HAS TRACKED NORTH-NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND AN 180037Z SSMIS 85 GHZ IMAGE DEPICT A DEEP CONVECTIVE SPIRAL FEEDER BAND WRAPPING INTO A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) FROM THE NORTHERN SEMI-CIRCLE. TS KHANUN'S DEEP CONVECTIVE STRUCTURE HAS NOT CHANGED OVER THE LAST SIX HOURS. THEREFORE, THE CURRENT INTENSITY IS MAINTAINED AT 50 KNOTS BASED ON A COMBINATION OF ANALOGOUS DVORAK ESTIMATES OF 55 KNOTS AND STEADY ADT ESTIMATES OF 47-51 KNOTS OVER THE PAST 16 HOURS. THE CURRENT POSITION IS BASED ON THE ABOVE MENTIONED IMAGERY WITH HIGH CONFIDENCE. THE SYSTEM CONTINUES TO TRACK BETWEEN THE WESTERN PERIPHERY OF A HIGH AMPLITUDE DEEP LAYER SUBTROPICAL RIDGE (STR) CENTERED SOUTH OF HONSHU, JAPAN, AND A STATIONARY MID-LATITUDE TROUGH OVER EASTERN ASIA. UPPER-LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH WEAK TO MODERATE (10-20 KNOTS) EASTERLY VERTICAL WIND SHEAR. ANIMATED WATER VAPOR IMAGERY SHOWS GOOD POLEWARD OUTFLOW INTO THE CREST OF THE HIGHLY AMPLIFIED STR AND EQUATORWARD OUTFLOW HAS BEEN SQUELCHED BY AN UPPER-LEVEL TROUGH LOCATED EAST OF TAIWAN EXTENDING EQUATORWARD TO LUZON. 3. FORECAST REASONING. A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 08W WILL CONTINUE TO TRACK WITHIN THE POLEWARD SYNOPTIC PATTERN DURING THE REMAINDER OF THE FORECAST PERIOD AND GRADUALLY WEAKEN. BY TAU 24, TS KHANUN WILL BE SURROUNDED BY COOLER (22-25C) SEA SURFACE TEMPERATURES AND BEGIN TO PERIPHERALLY INTERACT WITH THE SOUTHERN KOREAN PENINSULA. THESE UNFAVORABLE CONDITIONS WILL ONLY INCREASE INTO TAU 36 AS THE LLCC NEARS LANDFALL AND DISSIPATION OVERLAND IS EXPECTED BY TAU 36. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH THE FIRST 24 HOURS OF THE FORECAST PERIOD WITH INCREASING VORTEX TRACKER SPREAD OCCURRING OVERLAND. THE CURRENT CYCLE GFS AND ECMWF TRACK THE VORTEX TOWARDS A LOW-LEVEL MID-LATITUDE CIRCULATION, AND ASSOCIATED VORTICITY, FORMING OFF THE COAST OF HONSHU, JAPAN IN THE EXTENDED TAUS. IT SEEMS THE MAXIMUM ENERGY WITHIN THE POLAR FRONT JET IS SLIDING DOWN THE EASTERN PERIPHERY OF THE HIGH AMPLITUDE STR AND MAY CAUSE A RE- GENERATION OF THE MATURE MID-LATITUDE CYCLONE CURRENTLY SOUTH OF THE KAMCHATKA PENINSULA. HOWEVER, TS 08W IS NOT EXPECTED TO SURVIVE SUCH A JOURNEY OVER THE TERRAIN OF NORTH KOREA, MAINTAIN IT'S WARM CORE PROPERTIES IN A CONTINENTAL POLAR AIR MASS, OR MAINTAIN FORMATION UNDER THE EXPECTED HIGH VWS. THEREFORE, THE HIGH CONFIDENCE IN THE JTWC FORECAST TRACK REMAINS.// NNNN NNNN