WDPN31 PGTW 011500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (RUMBIA) WARNING NR 15// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 06W (RUMBIA), LOCATED APPROXIMATELY 217 NM SOUTHWESTWARD OF HONG KONG, HAS TRACKED WEST-NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS A SLIGHT WEAKENING TREND OVER THE PAST SIX HOURS; HOWEVER, THE SYSTEM HAS RETAINED TIGHTLY-CURVED BANDING (TCB) WRAPPING INTO THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 011202Z SSMIS IMAGE INDICATES A POSSIBLE WEAK MICROWAVE EYE FEATURE POSITIONED ON THE NORTHERN EDGE OF THE DEEP CONVECTION WITH EXPOSED, SHALLOW BANDING OVER THE NORTHERN QUADRANT DUE TO THE PERSISTENT, MODERATE TO STRONG (20 TO 30 KNOTS) VERTICAL WIND SHEAR (VWS). DUE TO THE TCB, THE DVORAK INTENSITY ESTIMATES HAVE INCREASED TO T4.0 FROM BOTH KNES AND PGTW, THEREFORE, THE INITIAL INTENSITY REMAINS ASSESSED AT 65 KNOTS. THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION BASED ON THE SSMIS IMAGE. ENVIRONMENTAL CONDITIONS ARE BECOMING INCREASINGLY MARGINAL WITH INCREASING VWS AND LAND INTERACTION WITH THE EASTERN COAST OF HAINAN ISLAND, WHICH IS DISRUPTING CONVECTIVE BANDING OVER THE WESTERN SEMI-CIRCLE. RECENT UPPER-AIR SOUNDINGS ON THE PERIPHERY OF THE SYSTEM VERIFY STRONG NORTHEASTERLY VWS. TY 06W CONTINUES TO TRACK QUICKLY ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP SUBTROPICAL RIDGE (STR). A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TY 06W IS FORECAST TO TRACK NORTHWESTWARD TO NORTH- NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH THE FORECAST PERIOD. THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK DUE TO THE TIGHT CLUSTER OF DYNAMIC MODELS WITH A 30-NM SPREAD IN SOLUTIONS AT TAU 12. THE MODELS DIVERGE SLIGHTLY AFTER LANDFALL BUT REMAIN IN CLOSE AGREEMENT. TY 06W HAS PEAKED IN INTENSITY AND IS FAST APPROACHING HAINAN ISLAND AND INCREASING VWS, SO THE SYSTEM IS FORECAST TO GRADUALLY WEAKEN UNTIL LANDFALL THEN WILL DISSIPATE BY TAU 36 OVER SOUTHERN CHINA. THE MESOSCALE MODELS, HWRF AND GFDN, NAILED THE PEAK INTENSITY FORECAST OF 65 KNOTS BUT NOW SUPPORT THE WEAKENING TREND IN ADDITION TO ALL THE OTHER RELIABLE INTENSITY GUIDANCE.// NNNN