MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W (GONI) WARNING NR 28// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 16W (GONI), LOCATED APPROXIMATELY 504 NM SOUTH- SOUTHWEST OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A 22-NM ROUND EYE, WHICH PROVIDES GOOD CONFIDENCE IN THE CURRENT POSITION. A 201806Z NOAA-19 89GHZ IMAGE DEPICTS AN ERODING EYEWALL OVER THE NORTHERN SEMI-CIRCLE WITH TIGHTLY-CURVED CONVECTIVE BANDING. UPPER-LEVEL ANALYSIS INDICATES NEAR-RADIAL OUTFLOW WITH WEAK CONVERGENT FLOW AND MODERATE NORTHERLY VERTICAL WIND SHEAR OVER THE NORTHERN PERIPHERY OF THE SYSTEM. THE CURRENT INTENSITY IS ASSESSED AT 105 KNOTS BASED ON A DVORAK CURRENT INTENSITY ESTIMATES OF T5.5 (102 KNOTS) FROM PGTW. TY 16W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A NARROW, EAST-WEST ORIENTED STR TO THE NORTH. THE STR IS RELATIVELY WEAK DUE TO THE PRESENCE OF THE TWO TROPICAL CYCLONES AS WELL AS A STRONG SUBTROPICAL WESTERLY JET PERSISTING OVER THE KOREAN PENINSULA AND JAPAN. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. WITHIN THE NEXT 12 HOURS, TY 16W IS FORECAST TO SLOW AS THE STR STEERING INFLUENCE TO THE NORTH WEAKENS. BASED ON THE RECENT 500MB ANALYSES, THE STR TO THE NORTH IS WEAKENING RAPIDLY AS THE WESTERLIES STRENGTHEN AND THE ANTICYCLONE OVER CHINA RETROGRADES. THE 20/12Z 500MB ANALYSIS SHOWS A BROAD WEAKENESS BETWEEN THE WESTERN AND EASTERN RIDGES. AFTER TAU 12, THE WESTERN BRANCH OF THE STR OVER CHINA IS EXPECTED TO WEAKEN FURTHER AND RECEDE WESTWARD, THEREFORE, TRACK MOTION THROUGH TAU 24 IS EXPECTED TO SLOW FURTHER WITH POSSIBLE QUASI-STATIONARY MOTION DUE TO THE WEAK STEERING ENVIRONMENT. DYNAMIC MODEL GUIDANCE IS UNANIMOUS IN DEPICTING A SIGNIFICANT SLOW DOWN WITH MAJOR DIFFERENCES IN THE TIMING OF THE POLEWARD TURN, THEREFORE, THERE IS UNCERTAINTY IN THIS PHASE OF THE SYSTEM. AFTER TAU 12, THE STR IS FORECAST TO RE-BUILD EAST OF THE SYSTEM PROVIDING A POLEWARD ORIENTED TRACK, WHICH SHOULD ALLOW THE SYSTEM TO SLOWLY TRACK NORTHWARD. AVAILABLE MODEL TRACKERS AND ENSEMBLE GUIDANCE SUPPORT THIS NORTHWARD TRACK. TY 16W SHOULD WEAKEN GRADUALLY THROUGH THE FORECAST PERIOD DUE TO LAND INTERACTION AND INCREASED UPPER-LEVEL CONVERGENCE ASSOCIATED WITH THE UPPER-LEVEL SUBTROPICAL WESTERLIES ENCROACHING ON THE WESTERN PERIPHERY OF THE SYSTEM. C. IN THE EXTENDED PERIOD, TY 16W WILL TURN NORTHEASTWARD AS IT TRACKS ALONG THE NORTHWESTERN PERIPHERY OF THE STR. DYNAMIC GUIDANCE IS IN POOR AGREEMENT, THEREFORE, THERE IS LOW OVERALL CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN