MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (LEKIMA) WARNING NR 29// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 10W (LEKIMA), LOCATED APPROXIMATELY 153 NM NORTH-NORTHWEST OF SHANGHAI, CHINA, HAS TRACKED NORTHWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A BROAD, DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION FLARING OVER THE EAST AND NORTH QUADRANTS. A 102256Z SSMIS 91GHZ IMAGE SHOWS BROAD, FRAGMENTED BANDING WRAPPING AROUND THE BROAD LLCC. OVERALL, THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS ASSESSED AT 45 KNOTS BASED ON THE CONVECTIVE STRUCTURE. UPPER-LEVEL ANALYSIS REVEALS LOW VERTICAL WIND SHEAR (5-10 KNOTS) AND STRONG POLEWARD OUTFLOW ENHANCED BY A SHORTWAVE TROUGH TO THE NORTHWEST. THEREFORE, INTERACTION WITH LAND AND FRICTIONAL EFFECTS ARE THE PRIMARY WEAKENING MECHANISM. TS 10W IS TRACKING ALONG THE WESTERN PERIPHERY OF A NORTH-SOUTH ORIENTED SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 10W IS FORECAST TO CONTINUE TRACKING NORTHWARD ALONG THE EASTERN COAST OF CHINA THROUGH TAU 48 ALONG THE WESTERN PERIPHERY OF THE STR. THE SYSTEM IS FORECAST TO RAPIDLY WEAKEN AS IT TRACKS OVER THE EASTERN COAST OF CHINA. NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK. AT TAU 48, TS 10W IS EXPECTED TO DISSIPATE DUE TO STRONG VERTICAL WIND SHEAR (30-40 KNOTS) AS IT TRACKS CLOSE TO THE UPPER-LEVEL JET ASSOCIATED WITH A DEEP SHORTWAVE TROUGH OVER NORTHEAST CHINA.// NNNN NNNN