MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 48// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 12W (LIONROCK), LOCATED APPROXIMATELY 382 NM SOUTH-SOUTHEAST OF MISAWA, JAPAN, HAS TRACKED NORTHWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS RAPIDLY DECAYING DEEP CENTRAL CONVECTION THAT IS DISPLACED JUST EAST OF THE LOW-LEVEL CIRCULATION CENTER. THE INITIAL POSITION IS BASED ON THE EIR LOOP AND ON A LOW REFLECTIVITY CIRCULATION FEATURE ON THE 291739Z AMSU-B MICROWAVE PASS WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 65 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF AGENCY AND OBJECTIVE DVORAK ESTIMATES AND REFLECTS THE WEAKENED STATE OF THE SYSTEM. UPPER LEVEL ANALYSIS INDICATES TY 12W IS SOUTH OF THE RIDGE AXIS IN AN AREA OF LOW TO MODERATE (10-15 KNOT) WESTERLY VERTICAL WIND SHEAR (VWS). ADDITIONALLY, A TROUGH TO THE WEST IS CAUSING SUBSIDENCE ALONG THE WESTERN SEMI-CIRCLE. THERE IS, HOWEVER, MODERATE SOUTHEASTWARD OUTFLOW. THESE DYNAMICS ARE EVIDENT ON EIR AND WATER VAPOR ANIMATIONS. THE CYCLONE IS TRACKING ALONG THE WESTERN PERIPHERY OF A RIDGE EXTENSION TO THE EAST. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE EXCEPT THAT THE TERMINATION PHASE OF THE FORECAST HAS BEEN CHANGED FROM EXTRA-TROPICAL TRANSITION TO DISSIPATION. B. TY LIONROCK IS EXPECTED TO BEGIN TRACKING MORE NORTHWESTWARD OVER THE NEXT 12 HOURS AS STEERING TRANSITIONS TO THE SUBTROPICAL RIDGE TO THE NORTHEAST ANCHORED NEAR 45N SOUTH OF KAMCHATKA. THE SYSTEM WILL CROSS JAPAN NEAR SENDAI AND DRIFT ACROSS THE SEA OF JAPAN (SOJ) BEFORE MAKING A FINAL LANDFALL IN RUSSIA NEAR VLADIVOSTOK. ALTHOUGH VWS IS EXPECTED TO RELAX BEFORE JAPAN, UPPER-LEVEL SUBSIDENCE AND COOLING SEA SURFACE TEMPERATURES (SSTS) WILL CONTINUE TO WEAKEN THE SYSTEM. AFTERWARD, RAPID DECAY IS EXPECTED AS THE SYSTEM TRACKS ACROSS RUGGED TERRAIN, COOLER SSTS, AND HIGH VWS (GREATER THAN 40 KNOTS) IN THE SOJ. TY 20W WILL DISSIPATE BEFORE IT MAKES LANDFALL IN RUSSIA. DYNAMIC GUIDANCE REMAINS IN TIGHT AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN