MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (LEKIMA) WARNING NR 24// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 10W (LEKIMA), LOCATED APPROXIMATELY 168 NM SOUTH OF SHANGHAI, CHINA, HAS TRACKED NORTH-NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A SLIGHT WEAKENING TREND WITH A COMPACT CENTRAL DENSE OVERCAST FEATURE. A 091446Z GMI 89GHZ IMAGE AND RADAR IMAGERY INDICATE CONCENTRIC EYEWALLS WITH SPIRAL BANDING. OVERALL, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. CURRENTLY, THERE ARE NO SURFACE OBSERVATIONS AVAILABLE NEAR THE CENTER, HOWEVER, A 09/15Z OBSERVATION FROM DACHEN DAO, APPROXIMATELY 25NM EAST OF THE CENTER, INDICATED 070/33 KNOTS WITH SLP NEAR 968.6MB. UPPER-LEVEL ANALYSIS REVEALS LOW VERTICAL WIND SHEAR AND ROBUST POLEWARD OUTFLOW ENHANCED BY A SHORTWAVE TROUGH TO THE NORTHWEST. THEREFORE, INTERACTION WITH LAND / FRICTIONAL EFFECTS ARE THE PRIMARY WEAKENING MECHANISM. TY 10W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 10W IS FORECAST TO TRACK NORTHWARD THROUGH TAU 72 ALONG THE WESTERN PERIPHERY OF THE STR, WHICH REORIENTS NORTH-SOUTH. 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 THIS PORTION OF THE JTWC FORECAST TRACK. C. AFTER TAU 72, TY 10W WILL TRACK UNDER STRONG SOUTHWESTERLY FLOW ASSOCIATED WITH A DEEP SHORTWAVE TROUGH OVER NORTHEAST CHINA, WHICH WILL FURTHER WEAKEN THE SYSTEM DUE TO INCREASING VERTICAL WIND SHEAR AND CONVERGENCE ALOFT. NUMERICAL MODEL GUIDANCE DIVERGES WITH SEVERAL MODELS JUMPING ERRONEOUSLY TO MIDLATITUDE VORTICITY CENTERS. THE REMAINDER OF THE GUIDANCE INDICATES A SLOW NORTHEASTWARD TRACK OVER THE GULF OF POHAI. TY 10W IS FORECAST TO DISSIPATE BY TAU 96 AS IT TRACKS CLOSE TO THE UPPER-LEVEL JET. OVERALL, TRACK CONFIDENCE REMAINS HIGH.// NNNN NNNN