MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (HAGIBIS) WARNING NR 025// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 20W (HAGIBIS), LOCATED APPROXIMATELY 406 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT SATELLITE FIXES FROM PGTW AND RJTD ON A 23 NM EYE. THE INTENSITY OF 115 KNOTS IS CONSISTENT WITH A CONSENSUS OF SUBJECTIVE DVORAK CURRENT INTENSITY AND OBJECTIVE ESTIMATES FROM MULTIPLE REPORTING AGENCIES. TYPHOON 20W HAS CONTINUED A SLOW WEAKENING TREND WHILE TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE OVER THE PAST SIX HOURS. A REORGANIZATION OF THE CONVECTIVE STRUCTURE IS ONGOING. CONVECTIVE BANDING ON THE PERIPHERY OF THE SYSTEM IS BECOMING SHALLOWER, BUT DEEP CONVECTION PERSISTS AROUND THE EYE. ENVIRONMENTAL ANALYSIS INDICATES LOW TO MODERATE (10-15 KNOT) VERTICAL WIND SHEAR, STRONG POLEWARD OUTFLOW ALOFT AND MARGINAL SEA SURFACE TEMPERATURES (ABOUT 27-28C). 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. THE FORECAST PERIOD HAS BEEN REDUCED TO 48 HOURS BASED ON THE TIMELINE OF ANTICIPATED EXTRATROPICAL TRANSITION. B. TY 20W WILL CONTINUE TO TRACK POLEWARD AND GRADUALLY TURN TOWARD THE NORTHEAST AFTER TAU 12 AS IT CONTINUES ALONG THE WESTERN PERIPHERY OF THE STEERING RIDGE. SLOW BUT STEADY WEAKENING IS EXPECTED PRIOR TO LANDFALL (JUST AFTER TAU 24) UNDER THE DUAL INFLUENCES OF INCREASING VERTICAL WIND SHEAR AND LAND INTERACTION WITH THE NORTHERN PORTION OF THE STORM CIRCULATION. THE SYSTEM CENTER IS EXPECTED TO PASS CLOSE TO THE TOKYO AREA AROUND TAU 30 BEFORE THE SYSTEM ACCELERATES QUICKLY OUT TO SEA TO THE EAST OF HONSHU AHEAD OF AN APPROACHING MID-LATITUDE TROUGH. TY 20W WILL BECOME FULLY EMBEDDED WITHIN THIS APPROACHING TROUGH AND TRANSITION INTO A STRONG EXTRATROPICAL LOW PRESSURE SYSTEM BY TAU 48. NUMERICAL MODEL TRACK FORECAST GUIDANCE REMAINS IN VERY GOOD AGREEMENT IN TERMS OF DIRECTION AND FORWARD SPEED. THERE IS HIGH CONFIDENCE TO THE JTWC FORECAST TRACK, WHICH LIES NEAR THE MULTI-MODEL CONSENSUS.// NNNN NNNN