MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (HAISHEN) WARNING NR 028// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 11W (HAISHEN), LOCATED APPROXIMATELY 119 NM NORTHEAST OF OSAN AB, SOUTH KOREA, HAS TRACKED NORTHWARD AT 29 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS MID-LEVEL CONVECTION SHEARED TO THE NORTHEAST OF THE LOW LEVEL CIRCULATION CENTER WHICH HAS ENTERED THE SEA OF JAPAN. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE PARTIALLY EXPOSED LOW LEVEL CIRCULATION IN THE MSI LOOP, AS WELL AS THE REMAINING CONVECTIVE BANDING THAT CONTINUES TO WRAP INTO A LOW LEVEL CIRCULATION FEATURE IN A 070426Z AMSR2 IMAGE. THE INITIAL INTENSITY OF 60 KTS IS PLACED WITH FAIR CONFIDENCE AND IS HEDGED SLIGHTLY BELOW MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T4.0 (65 KTS, RJTD AND PGTW) AND THE 64 KTS MAX WINDS PRESENT IN THE AMSR2 WIND PRODUCT DUE TO THE WEAKENING NATURE OF THE CONVECTION. ENVIRONMENTAL CONDITIONS REMAIN MARGINAL DUE TO HIGH (20+ KTS) VERTICAL WIND SHEAR, COOL (22-23 CELSIUS) SEA SURFACE TEMPERATURES, AND WEAKENING EQUATORWARD OUTFLOW. THE SYSTEM IS BEGINNING EXTRATROPICAL TRANSITION AS IT IS BECOMING EMBEDDED IN THE DEEP WESTERLY FLOW OF THE JET ALOFT. OF NOTE, THIS UPPER LEVEL WESTERLY FLOW IS OFFSETTING THE UNFAVORABLE ENVIRONMENTAL CONDITIONS SLIGHTLY, WHICH HAS LEAD TO ONLY MODEST WEAKENING OVER THE PAST 6 HOURS. THE CYCLONE IS CONTINUING TO TRACK ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE EAST. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE LAST PROGNOSTIC REASONING MESSAGE. B. TS HAISHEN WILL CONTINUE TO TRACK POLEWARD THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD UNDER THE STEERING INFLUENCE OF THE STR. BY TAU 12, THE SYSTEM WILL MAKE A SECOND LANDFALL OVER THE KOREAN PENINSULA. THE CONTINUED UNFAVORABLE ENVIRONMENTAL CONDITIONS OF HIGH VERTICAL WIND SHEAR, COOL SEA SURFACE TEMPERATURES WHILE OVER WATER AND INTERACTION WITH UNDERLYING TERRAIN WHILE OVER LAND WILL LEAD TO A DRAMATIC WEAKENING TO 35 KTS BY TAU 12, AT WHICH TIME IT WILL HAVE BECOME FULLY EMBEDDED IN THE BAROCLINIC ZONE AND COMPLETED EXTRATROPICAL TRANSITION. THE SYSTEM IS EXPECTED TO ONLY SLIGHTLY WEAKEN THEREAFTER AS IT BECOMES AS COLD CORE LOW OVER MANCHURIA. NUMERICAL MODEL SOLUTIONS ARE IN FAIR AGREEMENT AFTER TAU 12 DUE TO THE SPREAD IN TRACK GUIDANCE DUE TO THE INTERACTION OF THE SYSTEM WITH A MAJOR SHORTWAVE TROUGH ALOFT, HOWEVER THERE IS STILL HIGH CONFIDENCE IN THE OVERALL JTWC FORECAST TRACK THROUGH THE REMAINDER OF THE FORECAST PERIOD. NNNN NNNN