MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 21W (CHABA) WARNING NR 22// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 21W (CHABA), LOCATED APPROXIMATELY 100 NM SOUTH-SOUTHWEST OF KADENA AB, OKINAWA, JAPAN HAS TRACKED NORTH-NORTHWESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. STY CHABA HAS CONTINUED TO RAPIDLY INTENSIFY, NOW ASSESSED AT 145 KNOTS BASED ON SUBJECTIVE AND OBJECTIVE DVORAK INTENSITY ESTIMATES. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SHARP 5-NM EYE FEATURE SURROUNDED BY A VERY INTENSE CONVECTIVE CORE. THE POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE SEEN IN EIR AND RADAR IMAGERY. A 030544Z SSMI 85GHZ MICROWAVE IMAGE SHOWS A DEEP RING OF CONVECTION EXTENDING 25-NM FROM THE CENTER OF THE EYE. CONVECTIVE BANDING IS PRESENT ALONG THE WESTERN AND SOUTHERN PERIPHERIES OF THE STORM. THE WIND RADII HAVE BEEN ADJUSTED BASED ON A RECENT SCATTEROMETER PASS AND OBSERVATIONS FROM KADENA AB, OKINAWA AND MIYAKO-JIMA. STY 21W HAS STRENGTHENED DUE TO VERY WARM SEA SURFACE TEMPERATURES (SSTS) AND A ROBUST POLEWARD OUTFLOW CHANNEL ALONG THE LEADING EDGE OF AN APPROACHING MID-LATITUDE TROUGH CURRENTLY POSITIONED OVER EASTERN CHINA. HOWEVER, MICROWAVE AND SATELLITE IMAGERY ARE STARTING TO SHOW A TILT IN THE EYE OF THE SUPER TYPHOON DUE TO PERSISTENT 15 TO 20 KNOT SOUTHWESTERLY VERTICAL WIND SHEAR (VWS). STY 21W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. STY CHABA WILL CONTINUING MOVING TO THE NORTH-NORTHWEST AS IT PASSES TO THE WEST OF OKINAWA. AFTERWARDS, STY 21W WILL TURN NORTHWARD AND THEN NORTHEASTWARD AS IT ROUNDS THE STR AXIS. THE ROBUST OUTFLOW AND WARM SSTS WILL ALLOW FOR A SLIGHT INTENSIFICATION BEFORE THE INCREASING VWS FURTHER TILTS THE STORM AND BEGINS THE WEAKENING PHASE. THE STRONG ZONAL WESTERLY FLOW AND ASSOCIATED HIGH (30+ KNOT) VWS IS CURRENTLY SITUATED JUST SOUTH OF MAINLAND JAPAN AND SOUTH KOREA. STY CHABA WILL REACH THIS AREA NEAR TAU 36, WHICH WILL CAUSE THE SYSTEM TO ELONGATE TO THE NORTHEAST AND RAPIDLY WEAKEN. THE CYCLONE WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT EMBEDS WITHIN THE MID-LATITUDE WESTERLY FLOW ALONG THE WESTERN EDGE OF MAINLAND JAPAN. IT WILL CONTINUE TO WEAKEN AS IT TRACKS OVER THE COOL WATERS IN THE SEA OF JAPAN AND THEN ACROSS THE RUGGED JAPANESE TERRAIN. STY CHABA WILL COMPLETE ETT AS IT RE-EMERGES OVER THE WESTERN PACIFIC OCEAN. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGHOUT THE FORECAST. ADDITIONALLY, GLOBAL MODEL FIELDS SHOW NO CHANGE TO THE LOCATION OF THE MID-LATITUDE WESTERLIES; THEREFORE, ONLY MINIMAL CHANGES TO THE FORECAST TRACK ARE EXPECTED. GIVEN THESE FACTORS, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST.// NNNN NNNN