06W(KHANUN)to approach KYUSHU by 48/72H at Typhoon intensity//05E(DORA) powerful CAT 4 US//06E(EUGENE) intensifying//0521utc

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY, JMA RADAR DATA AND A 051732Z AMSR2 37GHZ MICROWAVE IMAGE INDICATE THAT TS 06W (KHANUN) HAS REMAINED REMARKABLY STABLE OVER THE PAST DAY, WITH NO MAJOR CHANGES IN STRUCTURE OR INTENSITY. THE SYSTEM REMAINS VERY LARGE, WITH A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) EMBEDDED WITHIN A BROAD REGION OF LIGHT WINDS, SURROUNDED BY A BAND OF STRONGER WINDS WITH A RADIUS OF MAXIMUM WINDS (RMW) OF ABOUT 85NM. THE AMSR2 IMAGE SHOWS WEAK CONVECTIVE BANDING ACROSS THE MAJORITY OF THE NORTHEASTERN QUADRANT, WITH MORE IMPRESSIVE CONVECTION PRESENT FROM NORTHWEST TO SOUTHEAST OF THE CENTER, CONFIRMED BY THE RADAR DATA. AN EARLIER 050922Z RCM-1 SAR PASS INDICATING MAXIMUM WINDS OF ABOUT 60 KNOTS ACROSS THE SOUTHERN PERIPHERY, WITH SOME ISOLATED AREAS OF WINDS UP TO 64 KNOTS IN THE SOUTHWEST QUADRANT. THE SAR PROVIDES HIGH CONFIDENCE TO THE INITIAL INTENSITY, EVEN THOUGH THE BULK OF THE OBJECTIVE AND SUBJECTIVE DVORAK-BASED INTENSITY ESTIMATES ARE READING MUCH LOWER. THE SYSTEM HAS SLOWED SIGNIFICANTLY AS IT HAS APPROACHED THE CHANNEL BETWEEN TOKUNOSHIMA AND AMAMI OSHIMA ISLANDS BUT OVERALL CONTINUES TRACKING EASTWARD ALONG THE NORTHERN EDGE OF A NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST. THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE, WITH LOW VERTICAL WIND SHEAR (VWS) OFFSET BY CONTINUED UPWELLING DUE TO THE SLOW FORWARD MOTION, WEAK OUTFLOW ALOFT, AND DRY MID-LEVEL AIR OVER TOP OF THE SYSTEM.

050922Z RCM-1 SAR PASS INDICATING MAXIMUM WINDS OF ABOUT 60 KNOTS ACROSS THE SOUTHERN PERIPHERY, WITH SOME ISOLATED AREAS OF WINDS UP TO 64 KNOTS IN THE SOUTHWEST QUADRANT.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: AFTER MAKING A BRIEF PIT STOP AS IT PASSED THE RYUKU ISLANDS, OVER THE NEXT FEW HOURS, TS 06W WILL MOVE INTO THE PHILIPPINE SEA, THOUGH TRACK SPEEDS ARE EXPECTED TO REMAIN RELATIVELY SLOW. ONCE CLEAR OF THE ISLANDS, THE SYSTEM WILL MODESTLY ACCELERATE TOWARDS THE EAST-NORTHEAST UNDER THE STEERING INFLUENCE OF THE NER TO THE SOUTH. BY TAU 36, THE SYSTEM REACHES ANOTHER INFLECTION POINT IN THE STEERING REGIME, SLOWS DOWN TO NEAR QUASI-STATIONARY SPEEDS AND BEGINS TO TURN NORTHWARD. BY TAU 48, THE STRONG SUBTROPICAL RIDGE (STR) CENTERED FAR OUT IN THE NORTHERN PACIFIC TAKES OVER THE DOMINATE STEERING ROLE AND EJECTS TS 06W ON A NORTH-NORTHWESTWARD TRACK WHICH TRACKS VERY CLOSE TO THE SOUTHERN TIP OF KYUSHU BY TAU 72. THE STR IS FORECAST TO BUILD AND PUSH WESTWARD AFTER TAU 72, WHICH WILL DRIVE TS 06W ONTO A GENERALLY NORTHWARD TRACK AFTER TAU 72, CROSSING VERY CLOSE TO SASEBO BEFORE EMERGING INTO THE TSUSHIMA STRAIT BY TAU 96, THEN TRACKING UP THE EAST COAST OF THE KOREAN PENINSULA THROUGH TAU 120. WHILE THE SYSTEM HAS MOVED OUT OF THE REGION OF MOST INTENSE UPWELLING, THE CONTINUED SLOW TRACK SPEEDS MEAN THAT UPWELLING IS STILL AN ISSUE. COMBINED WITH THE DRY MID-LEVEL AIR THAT CURRENTLY LIES OVER TOP OF THE SYSTEM, AND THE LACK OF MUCH OF AN OUTFLOW CHANNEL, THE SYSTEM IS EXPECTED TO WEAKEN SLIGHTLY THROUGH THE NEXT 12 TO 24 HOURS. BY TAU 24, IT WILL HAVE MOVED FAR ENOUGH INTO THE PHILIPPINE SEA TO ACCESS WARMER, HIGHER OHC WATERS, OUTFLOW BEGINS TO IMPROVE AND THE DRY AIR IS EXPECTED TO MOISTEN UP A BIT, WHICH WILL ALLOW THE SYSTEM TO EMBARK ON A SLOW INTENSIFICATION TREND, THE PACE OF WHICH WILL BE LIMITED BY THE EXPANSIVE DIAMETER OF THE CIRCULATION. BY TAU 48, THE CIRCULATION IS FORECAST TO DECREASE IN SIZE, SSTS WILL BE AT THEIR WARMEST (29C) AND THE SYSTEM BEGINS TO TAP INTO A POLEWARD OUTFLOW CHANNEL AHEAD OF AN APPROACHING UPPER-LEVEL TROUGH, TRIGGERING A BURST OF INTENSIFICATION UP TO 70 KNOTS AS THE SYSTEM APPROACHES LANDFALL. PASSAGE OVER KYUSHU WILL LEAD TO A GENERALIZED WEAKENING DUE TO TERRAIN INTERACTION, WHICH IS EXPECTED TO CONTINUE AS THE SYSTEM MOVES NORTH JUST EAST OF THE KOREAN PENINSULA. BY TAU 120 THE SYSTEM BEGINS EXTRATROPICAL TRANSITION (ETT) AS IT INTERACTS WITH A SHARP 500MB TROUGH AND ASSOCIATED BAROCLINIC ZONE.

MODEL DISCUSSION: DETERMINISTIC TRACK SPREAD CONTINUES TO EXPAND WITH THIS RUN, WITH THREE DISTINCT GROUPINGS; THE NAVGEM AND COAMPS-TC (NAVGEM) CONTINUE TO BE THE EASTERN OUTLIERS, TAKING THE SYSTEM OVER SHIKOKU AND INTO THE EASTERN SEA OF JAPAN. THE UKMET AND UKMET ENSEMBLE MARK THE WESTERN GROUPING, TAKING THE SYSTEM OVER CHEJU DO AND NEAR PYONGYANG. THE REMAINDER OF THE CONSENSUS MEMBERS MAKE UP THE THIRD GROUPING, WHICH LIE WITHIN A 75NM WIDE ENVELOPE AT TAU 48. BY TAU 120, CROSS-TRACK SPREAD BETWEEN THE OUTLIERS IS NEARLY 600NM. BUT EVEN THE INNER NEXT OF MODELS BEGINS TO SPREAD OUT, AND BY TAU 120 THE SPREAD OF THESE MODELS IS 230NM. THE GFS AND ECMWF TRACKERS NOW KEEP THE CENTER OFFSHORE TO THE WEST OF KYUSHU, WITH LANDFALL NEAR BUSAN AROUND TAU 96, FOLLOWED BY A TRACK THROUGH THE CENTER OF THE KOREAN PENINSULA, WHILE THE GEFS, EGRR, HAFS-A AND THE CONSENSUS MEAN TRACK OVER WESTERN KYUSHU AND THE EASTERN PORTION OF THE KOREAN PENINSULA. THE JTWC TRACK HAS SHIFTED SIGNIFICANTLY TO THE WEST, ESPECIALLY AFTER TAU 72 IN LIGHT OF THE SHIFT WEST OF THE BULK OF THE GUIDANCE. INTENSITY GUIDANCE IS IN FAIR AGREEMENT, WITH THE HAFS-A AND GFS SHOWING THE NEAR-TERM WEAKENING, FOLLOWED BY VARYING DEGREES OF INTENSIFICATION. THE COAMPS-TC AND HWRF CONTINUE TO BE THE MOST AGGRESSIVE MODELS, PEAKING THE SYSTEM NEAR 90 KNOTS BY TAU 60 WHILE THE REMAINDER OF THE MODELS PEAK BETWEEN 60-70 KNOTS.