WDPN31 PGTW 090900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W (CHAN-HOM) WARNING NR 019// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 16W (CHAN-HOM), LOCATED APPROXIMATELY 413 NM SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS OF DEEP CONVECTION WRAPPING INTO AN OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE BANDING IN THE MSI LOOP AS WELL AS THE LOW LEVEL FEATURES PRESENT IN A 090438Z ATMS 88.2GHZ IMAGE. THE INITIAL INTENSITY OF 70 KTS IS PLACED WITH HIGH CONFIDENCE AND IS HEDGED BETWEEN MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T4.0 (65 KTS, PGTW), T4.5 (77 KTS, RJTD) AND A 090437Z CIMSS SATCON INTENSITY ESTIMATE OF 65 KTS. TY CHAN-HOM IS TRACKING ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST AND THROUGH AN OVERALL UNFAVORABLE ENVIRONMENT WITH MODERATE TO HIGH (25 KTS) VERTICAL WIND SHEAR (VWS) OFFSET BY WARM (27-28 CELSIUS) SEA SURFACE TEMPERATURES (SST) AND ROBUST POLEWARD OUTFLOW ALOFT, ENHANCED BY THE JET POSITIONED TO THE NORTH OVER JAPAN. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY CHAN-HOM WILL TRACK GENERALLY EAST-NORTHEASTWARD OVER THE NEXT 24 HOURS. DURING THIS TIME, THE SYSTEM WILL GRADUALLY WEAKEN TO 55 KNOTS BY TAU 24, LARGELY DUE TO INCREASING VWS WHICH IS EXPECTED EXCEED 30 KTS BY TAU 24. AFTER THIS TIME, THE TRACK WILL BECOME GENERALLY EAST-NORTHEASTWARD TO EASTWARD AS THE SYSTEM TRACKS ALONG THE NORTHERN PERIPHERY OF THE STEERING STR AND APPROACHES THE BAROCLINIC ZONE. BY TAU 36, CONTINUED HIGH VWS WILL LEAD TO FURTHER WEAKENING TO 50 KTS AS THE SYSTEM BEGINS EXTRATROPICAL TRANSITION. BY TAU 72, THE SYSTEM WILL BECOME FULLY EMBEDDED IN THE AFOREMENTIONED WESTERLY FLOW ALOFT AND WILL COMPLETE ETT, BECOMING A COLD CORE LOW. NUMERICAL MODEL SOLUTIONS HAVE CONTINUED TO STRUGGLE WITH THE LATER PORTION OF THE TRACK FOR TY 16W, HOWEVER THEY ARE BEGINNING TO CONVERGE ON A SOLUTION WHICH BRINGS THE CYCLONE CENTER ON A SOUTHEASTWARD TRACK AFTER TAU 36 DUE TO A REPOSITIONING OF THE STEERING RIDGE AFTER THIS TIME. SPECIFICALLY, THERE IS A 160 NM SPREAD IN ACROSS TRACK SOLUTIONS AT TAU 36 THAT INCREASES TO 585 NM BY TAU 72. DUE TO THE THE LARGE SPREAD IN MODEL SOLUTIONS THERE IS OVERALL POOR CONFIDENCE IN THE JTWC FORECAST, WHICH IS PLACED CLOSE TO THE JTWC MULTI-MODEL CONSENSUS.// NNNN