MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (NEOGURI) WARNING NR 20// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 08W (NEOGURI), LOCATED APPROXIMATELY 189 NM SOUTH- SOUTHWEST OF KADENA AB, OKINAWA, HAS TRACKED NORTH-NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY IN COMBINATION WITH RADAR IMAGERY FROM ISHIGAKIJIMA DEPICT A SLOW WEAKENING TREND FOR THE ENTIRE EYEWALL BUT WITH GREATER IMPACT ALONG THE NORTHWESTERN QUADRANT. THE CURRENT INTENSITY OF 110 KNOTS IS SLIGHTLY HIGHER THAN THE DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD, WHICH RANGE FROM 90 TO 102 KNOTS. THE EYE DIAMETER HAS DECREASED FROM 40 TO 30 NM OVER THE PAST SIX HOURS, BUT ANIMATED WATER VAPOR IMAGERY SUGGESTS THE EYEWALL HAS STABILIZED IN THE PAST FEW HOURS. A DIGGING MID-LATITUDE TROUGH, TO THE NORTHWEST OF TY 08W, HAS BEEN AMPLIFYING THE UPPER LEVEL POLEWARD OUTFLOW OVER THE PAST 12 HOURS, HELPING TO MAINTAIN THE INTENSITY OF THE SYSTEM. RECENTLY, AS THE TROUGH CONTINUES TO DIG TO THE SOUTHWEST OVER EASTERN CHINA, INCREASED SUBSIDENCE ALONG THE NORTHWESTERN QUADRANT OF TY 08W HAS HINDERED DEVELOPMENT AND IS LEADING TO THE WEAKENING OBSERVED IN THE PAST SIX HOURS. THE TRACK HAS SHIFTED SLIGHTLY MORE TO THE WEST THAN THE PREVIOUS FORECAST SUGGESTED AS TY 08W TRACKS ALONG THE SOUTH- WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) ANCHORED NEAR IWO TO. TRACK SPEEDS HAVE BEEN CONSISTENT OVER THE PAST 12 HOURS. 3. FORECAST REASONING. A. THIS FORECAST HAS SEVERAL PHILOSOPHY CHANGES AS MODEL GUIDANCE, RECENT OBSERVATIONS, AND SATELLITE IMAGERY SUPPORT A CHANGE. THE PRIMARY CHANGE IS ASSOCIATED WITH THE INTENSITY FORECAST. THE PREVIOUS FORECAST INDICATED AN EYEWALL REPLACEMENT CYCLE WAS UNDER WAY, AND THIS FORECAST SHIFTS TO A STEADY WEAKENING TREND WITH NO EXPECTATION OF AN INCREASE IN THE INTENSITY OVER THE NEXT 12 TO 24 HOURS. ADDITIONALLY, THE WEAKENING TREND WAS ACCELERATED AFTER TY 08W MAKES LANDFALL. THE SECOND CHANGE IS TO THE TRACK SPEED BEYOND TAU 36. BASED ON THE MODEL GUIDANCE, TRACK SPEEDS HAVE BEEN DECREASED AT THE TAU 48, 72 AND 96 TIMES. B. TY 08W IS FORECAST TO SHIFT TO A MORE NORTHWARD TRACK OVER THE NEXT 12 HOURS AND REMAIN ON A STEADY NORTHWARD TRACK THROUGH TAU 24. THE DIGGING MID-LATITUDE TROUGH TO THE NORTHWEST OF TY 08W WILL TRACK EASTWARD AND CAUSE THE STR TO SHIFT AFTER TAU 24, CAUSING TY 08W TO TRACK MORE NORTHEASTWARD AFTER TAU 36. THE TROUGH HAS BEEN AMPLIFYING THE UPPER LEVEL POLEWARD OUTFLOW OVER THE PAST 12 HOURS, HELPING TO MAINTAIN THE INTENSITY OF THE SYSTEM BUT AS IT SHIFTS EASTWARD, THE TROUGH WILL STIFLE THE STRONG POLEWARD OUTFLOW, LEADING TO A STRONGER WEAKENING TREND BY TAU 48. THE TIMING OF LANDFALL IN SOUTHERN JAPAN HAS BEEN SHIFTED FROM THE PREVIOUS FORECAST AND IS EXPECTED AROUND 00Z ON THE 10TH. THE SEA SURFACE TEMPERATURES REMAIN VERY FAVORABLE THROUGH TAU 24, BUT WILL QUICKLY DECREASE ONCE THE SYSTEM APPROACHES 30N. INCREASING VERTICAL WIND SHEAR FROM THE MID-LATITUDE WESTERLIES WILL ALSO BEGIN TO IMPACT THE STRUCTURE OF TY 08W AFTER TAU 36. BEYOND TAU 48 A COMBINATION OF THESE ELEMENTS, IN ASSOCIATION WITH THE TRACK OVER THE SOUTHERN JAPANESE TERRAIN, WILL LEAD TO A THE BEGINNING OF EXTRA-TROPICAL TRANSITION (ETT) BY TAU 72. C. BEYOND TAU 72, TY NEOGURI WILL CONTINUE THE ETT PROCESS, ACCELERATING TO THE NORTHEAST UNDER THE COMBINED INFLUENCE OF A DEEP MID-LATITUDE LOW OVER NORTHERN JAPAN AND THE STR. TY NEOGURI IS EXPECTED TO BY FULLY EXTRA-TROPICAL BY TAU 96. THE AVAILABLE DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT, LENDING TO HIGH CONFIDENCE IN THE JTWC TRACK FORECAST TO THE MULTI-MODEL CONSENSUS.// NNNN NNNN