MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (HAISHEN) WARNING NR 019// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 11W (HAISHEN), LOCATED APPROXIMATELY 273 NM EAST- SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED A WELL-DEFINED 28-NM ROUND EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE. THE INITIAL INTENSITY OF 125 KTS IS BASED ON AN OVERALL ASSESSMENT OF MULTI- AGENCY DVORAK ESTIMATES RANGING FROM T6.0 (115 KTS) TO T6.5 (127 KTS) AND REFLECTS THE WEAKENING TREND. TY 11W IS STILL IN AN OVERALL FAVORABLE ENVIRONMENT WITH LOW (05-10KT) NORTHEASTERLY VERTICAL WIND SHEAR (VWS), EXCELLENT RADIAL OUTFLOW, AND WARM (30-31C) SEA SURFACE TEMPERATURES (SST). HOWEVER, A MAJOR SHORTWAVE TROUGH APPROACHING FROM THE NORTHWEST IS BEGINNING TO CAUSE SUBSIDENCE AND EROSION ALONG THE NORTHWEST QUADRANT. THE CYCLONE IS TRACKING UNDER THE STEERING INFLUENCE OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST, NOW EAST- SOUTHEAST OF HOKKAIDO, JAPAN. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE LAST PROGNOSTIC REASONING MESSAGE. B. THE APPROACHING SHORTWAVE TROUGH WILL WEAKEN THE STEERING STR AND ALLOW TY 11W TO TRACK MORE NORTH-NORTHWESTWARD, PASS JUST TO THE WEST OF KYUSHU, JAPAN, ACROSS THE KOREA STRAIT, MAKE LANDFALL JUST SLIGHTLY WEST OF BUSAN, SOUTH KOREA SHORTLY AFTER TAU 48, THEN DRAG NORTHWARD ALONG THE RUGGED MOUNTAIN RANGES OF THE KOREAN PENINSULA. INCREASING VWS, COOLING SSTS, AND EVENTUALLY, LAND INTERACTION WILL GRADUALLY THEN RAPIDLY ERODE THE SYSTEM, AND BY TAU 72 WILL BE REDUCED TO 30 KTS AFTER IT CROSSES INTO NORTH KOREA. CONCURRENTLY, THE CYCLONE WILL BEGIN EXTRA- TROPICAL TRANSITION AROUND TAU 48 AS IT ENTERS THE BAROCLINIC ZONE AND TRANSFORM INTO A COLD CORE LOW BY TAU 72. NUMERICAL MODELS REMAIN IN TIGHT AGREEMENT WITH JGSM AND ECMWF OUTLYING TO THE RIGHT OF THE MAIN PACK BEYOND TAU 36. THERE IS OVERALL HIGH CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID JUST LEFT OF THE MULTI-MODEL CONSENSUS BEYOND TAU 36 TO OFFSET THE OUTLIERS.// NNNN NNNN