MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (MAYSAK) WARNING NR 009// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 10W (MAYSAK), LOCATED APPROXIMATELY 566 NM SOUTH OF KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS TIGHTLY-CURVED BANDING WRAPPING INTO A CONSOLIDATING LOW- LEVEL CIRCULATION CENTER (LLCC). A 292150Z GMI 37GHZ COLOR COMPOSITE IMAGE DEPICTS A THICK CYAN RING, INDICATIVE OF AN IMMINENT RAPID INTENSIFICATION PHASE, AND A WELL-DEFINED MICROWAVE EYE FEATURE, WHICH SUPPORTS THE INITIAL POSITION AND RECENT TRACK MOTION WITH GOOD CONFIDENCE. UPPER-LEVEL ANALYSIS INDICATES A VERY FAVORABLE ENVIRONMENT WITH AN ENHANCED POLEWARD OUTFLOW CHANNEL INTO A BROAD UPPER LOW POSITIONED TO THE NORTHEAST, GOOD EQUATORWARD OUTFLOW AND LOW VERTICAL WIND SHEAR (VWS). ADDITIONALLY, SST VALUES (30-31C) AND HIGH OCEAN HEAT CONTENT VALUES ARE CONDUCIVE FOR FURTHER DEVELOPMENT. THE 29/12Z 500MB ANALYSIS INDICATES AN UPPER LOW NEAR 25N 135E ASSOCIATED WITH THE AFOREMENTIONED BROAD 200MB LOW; THIS SYNOPTIC ENVIRONMENT HAS LED TO A WEAK STEERING ENVIRONMENT WITH SLOW / QUASI-STATIONARY TRACK MOTION OVER THE PAST DAY. CURRENTLY, THE SYSTEM HAS TURNED ONTO A SLOW NORTHWESTWARD TRACK. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. THE UPPER LOW TO THE NORTHEAST IS FORECAST TO TRACK WESTWARD WHILE WEAKENING OVER THE NEXT SIX HOURS AS IT TRACKS ALONG THE NORTHERN PERIPHERY OF TY 10W. THIS WILL ALLOW THE STEERING SUBTROPICAL RIDGE (STR) TO BUILD EAST OF THE SYSTEM SUPPORTING A STEADY NORTHWARD TO NORTH-NORTHWESTWARD TRACK THROUGH TAU 48. THE PRESENCE OF AN EXTENSION OF THE STR TO THE NORTH, OVER WESTERN JAPAN AND THE KOREAN PENINSULA WILL ALSO INFLUENCE THE FORECAST TRACK PRODUCING A NORTH-NORTHWESTWARD TRACK THROUGH TAU 60 AS THE SYSTEM SKIRTS TO THE WEST OF OKINAWA. THE STR EXTENSION SHOULD ERODE AFTER TAU 60 WITH THE APPROACH OF A DEEP MIDLATITUDE SHORTWAVE TROUGH OVER EASTERN CHINA THEREFORE TY 10W SHOULD TRACK MORE POLEWARD. WITH THE EXCEPTION OF AFUI, NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT AT TAU 60 (WEST OF OKINAWA) WITH A 90NM SPREAD IN SOLUTIONS. UNDER VERY FAVORABLE CONDITIONS, TY 10W IS FORECAST TO RAPIDLY INTENSIFY OVER THE NEXT 36 HOURS WITH A PEAK INTENSITY OF 120 KNOTS AT TAU 36. SLIGHT WEAKENING IS ANTICIPATED BY TAU 72 AS SST VALUES COOL SLIGHTLY TO 28-29C. C. IN THE EXTENDED PERIOD, TY 10W IS FORECAST TO ACCELERATE NORTH- NORTHEASTWARD AS IT BEGINS EXTRA-TROPICAL TRANSITION (ETT) AND BEGINS TO INTERACT WITH THE AFOREMENTIONED MIDLATITUDE SHORTWAVE TROUGH. SIGNIFICANT WEAKENING WILL OCCUR AFTER TAU 90 AS THE SYSTEM TRACKS OVER THE MOUNTAINOUS KOREAN PENINSULA AND ENCOUNTERS INCREASING VWS ASSOCIATED A MIDLATITUDE JET. TY 10W WILL COMPLETE ETT BY TAU 120 AS IT GAINS FRONTAL CHARACTERISTICS AND TRACKS UNDER THE JET. NUMERICAL MODELS DIVERGE WITH A 185NM SPREAD IN SOLUTIONS AT TAU 120. THE JTWC FORECAST TRACK IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS, CLOSER TO THE ECMWF / EEMN SOLUTIONS. OVERALL THERE IS FAIR CONFIDENCE IN THE JTWC FORECAST TRACK DUE TO THE ERRATIC INITIAL MOTION AND UNCERTAINTY IN EXTENDED PERIOD.// NNNN NNNN