Typhoon 06W(KHANUN) peaks at CAT 4 US CPA to OKINAWA within 12/24h// TC 04B to landfall near KUAKATA/BANGLADESH//0103utc

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: AFTER A RECENT SHORT-TERM BOUGHT OF WEAKENING, TYPHOON (TY) 06W (KHANUN) HAS ONCE AGAIN EXHIBITED SIGNS OF SLIGHT INTENSIFICATION. DEEP CONVECTION HAS ONCE MORE FLARED UP AND ROTATED UPSHEAR, REESTABLISHING A SOLID EYEWALL ON THE NORTHWESTERN SIDE, WHERE PREVIOUS MICROWAVE IMAGERY SUGGESTED A FRAGMENTARY EYEWALL. WHILE HIGH-RESOLUTION MODEL CROSS-SECTIONS AND THE MOST RECENT SOUNDING FROM MINAMI DAITO JIMA STILL SHOW A WEDGE OF DRY AIR CENTERED AT ABOUT 300MB, THE FLARE UP OF CONVECTION ON THE NORTHERN SIDE HAS PUSHED BACK AGAINST THIS INTRUSION AND ALLOWED THE SYSTEM TO INTENSIFY. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON A 25NM WIDE EYE IN THE VISIBLE AND INFRARED SATELLITE IMAGERY. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON THE OVERALL AGREEMENT OF BOTH OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES INCLUDING THE DPRINT AND DMINT ESTIMATES OF 119 KNOTS AND 123 KNOTS RESPECTIVELY. HOWEVER, CONFIDENCE IS JUST MEDIUM IN LIGHT OF A SIGNIFICANT DIFFERENCE BETWEEN A 312129Z SMAP PASS SHOWING A MAXIMUM 1-MIN CONVERTED WIND OF 81 KNOTS AND A SAR PASS FROM 310914Z WITH A MAXIMUM OF 91 KNOTS. THE VERY LARGE DISCREPANCIES IN THE AVAILABLE INTENSITY ESTIMATES INTRODUCING A FAIR AMOUNT OF UNCERTAINTY IN THE INITIAL INTENSITY. THE SYSTEM HAS STARTED TO TRACK ON A MORE WEST-NORTHWEST (300 DEG VICE THE EARLIER 315 DEG), AS THE STEERING SHIFTS TO THE SUBTROPICAL RIDGE (STR) CENTERED OVER THE BOHAI GULF. THE OVERALL ENVIRONMENT REMAINS FAVORABLE, WITH LOW NORTHERLY SHEAR AND WARM SSTS THOUGH UPPER-LEVEL OUTFLOW IS A BIT LESS ROBUST THAN SEEN IN PREVIOUS ANALYSES, WITH THE SYSTEM STILL TAPPING INTO AN OUTFLOW CHANNEL INTO THE TUTT-CELL SOUTHWEST OF SHANGHAI. OTHERWISE OUTFLOW IS RESTRICTED TO RELATIVELY WEAK EQUATORWARD FLOW AND LOCALIZED RADIAL OUTFLOW IN THE VICINITY OF THE SYSTEM ITSELF.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY KHANUN HAS STARTED TO BEND ONTO A MORE WEST-NORTHWESTWARD TRACK NOW THAT THE PRIMARY STEERING MECHANISM HAS SHIFTED OVER TO THE DEEP-LAYER STR TO THE NORTH. THIS GENERAL MOTION IS EXPECTED TO CONTINUE THROUGH THE FIRST 48 HOURS OF THE FORECAST, THOUGH TRACK SPEEDS ARE EXPECTED TO BEGIN TO SLOW DOWN AFTER TAU 24 AS THE UPPER-LEVEL STEERING PATTERN BEGINS TO WEAKEN. AFTER ROUGHLY TAU 36, THE STR TO THE NORTH WILL SLIDE TO THE SOUTHWEST, WHILE SIMULTANEOUSLY A NEAR EQUATORIAL RIDGE (NER) BUILDS IN TO THE SOUTHEAST AND THE STR TO THE EAST REMAINS FIRMLY ENTRENCHED TO THE EAST OF JAPAN, TRAPPING TY 06W IN THE MIDDLE OF A WEAK AND COMPETING STEERING PATTERN. AS A RESULT, BY TAU 48, TY 06W WILL BECOME QUASI-STATIONARY AND MEANDERING ERRATICALLY IN THE CENTRAL PORTION OF THE EAST CHINA SEA. BY TAU 96 THE SYSTEM WILL BEGIN TO SLOWLY TRACK NORTHEASTWARD AS THE NER TO THE SOUTH ASSUMES THE DOMINATE STEERING ROLE. WHILE THE FORECAST TRACK CALLS FOR A TURN TO THE NORTHEAST, IT MUST BE REITERATED THAT TRACK SPEEDS ARE VERY LOW, LESS THAN 3 KNOTS FOR THE BULK OF FORECAST AFTER TAU 48, AND ERRATIC AND HIGHLY UNCERTAIN TRACK MOTIONS SHOULD BE ANTICIPATED. TY 06W HAS LIKELY REACHED PEAK INTENSITY AND IS EXPECTED TO MAINTAIN ITS CURRENTLY INTENSITY FOR THE NEXT 6 TO 12 HOURS AS IT PASSES TO THE SOUTHWEST OF OKINAWA. AFTER PASSING OKINAWA THE SYSTEM WILL BEGIN A GRADUAL WEAKENING TREND DUE TO REDUCED OUTFLOW ALOFT, PERSISTENT DRY AIR INTRUSION FROM THE NORTH AND A MODEST INCREASE IN SHEAR. AS THE SYSTEM BECOMES QUASI-STATIONARY AROUND TAU 48, THE SYSTEM GENERATE SIGNIFICANT UPWELLING, WITH THE HAFS-A DEPICTING SST REDUCTIONS ON THE ORDER OF 4C OR MORE IN THE EAST CHINA SEA, LEADING TO A RAPID WEAKENING TREND AFTER TAU 48.

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD CROSS-TRACK AGREEMENT THROUGH THE FIRST 48 HOURS OF THE FORECAST, THOUGH ALONG-TRACK SPREAD INCREASES SHARPLY AFTER TAU 48 AS THE MODELS DISAGREE ON THE TRACK SPEEDS AND HOW FAR WEST THE SYSTEM REACHES BEFORE TURNING BACK TO THE EAST. THE UKMET AND UKMET ENSEMBLE CONTINUE TO TRACK THE SYSTEM INTO EASTERN CHINA, WHILE THE REMAINDER OF THE CONSENSUS MEMBERS INDICATE A SHARP TURN BACK TO THE EAST-NORTHEAST BEGINNING BY TAU 72. THE HAFS-A, JGSM, AND ECMWF TAKE THE SYSTEM A BIT FURTHER WEST (AROUND 123E) BY TAU 72, WHILE THE GFS AND GEFS BEGIN FURTHER EAST. HOWEVER, BY TAU 120, THE ECMWF, GFS, NAVGEM AND THEIR ENSEMBLE MEANS COME INTO CONCURRENCE ON A REACHING A POSITION WEST OF AMAMI OSHIMA. DISCOUNTING THE UKMET MODELS, THE CONSENSUS ENVELOPE REACHES 225NM BY TAU 120. ENSEMBLE GUIDANCE DISPLAYS VERY HIGH UNCERTAINTY, WITH A WIDE SPREAD IN THE ENSEMBLE TRACK MEMBERS, PARTICULARLY AFTER TAU 96, LENDING LOW CONFIDENCE IN THE JTWC FORECAST AFTER TAU 48. INTENSITY GUIDANCE IS IN FAIRLY GOOD AGREEMENT, WITH THE JTWC FORECAST LYING ON THE UPPER END OF THE GUIDANCE ENVELOPE THROUGH THE FORECAST PERIOD WITH MEDIUM CONFIDENCE IN THE EARLY PORTION OF THE FORECAST AND LOW CONFIDENCE THEREAFTER DUE TO THE LARGE UNCERTAINTIES IN THE AMOUNT AND STRENGTH OF THE UPWELLING AND THE IMPACT THAT WILL HAVE ON THE INTENSITY.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH SPOTTY CONVECTION FLARING UP ON THE WESTERN AND SOUTHERN SIDES OF THE CIRCULATION. ANIMATED RADAR DATA FROM BANGLADESH SHOWS THE LLCC TO GOOD EFFECT, AND COMBINED WITH THE MSI IMAGERY, PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY REMAINS SET AT 40 KNOTS WITH MEDIUM CONFIDENCE, HEDGED SLIGHTLY HIGHER THAN THE AGENCY DVORAK INTENSITY ESTIMATES OF T2.0 (30 KNOTS) FROM BOTH PGTW AND KNES, IN PERSISTENCE WITH EARLIER SCATTEROMETER DATA. CIMSS ANALYSIS REVEALS A SIGNIFICANT INCREASE IN NORTHEASTERLY SHEAR, NOW UP TO 25-30 KNOTS, BUT THE UPPER-LEVEL FLOW REMAINS DIVERGENT IN THE VICINITY OF THE CIRCULATION, PROVIDING SOME EXHAUST FOR THE FLARING CONVECTION. OUTSIDE OF THE SHEAR, THE ENVIRONMENT REMAINS SUPPORTIVE, WITH VERY WARM SSTS AND ROBUST EQUATORWARD OUTFLOW.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 04B (FOUR) IS FORECAST TO TRACK NORTHWESTWARD ALONG THE WESTERN SIDE OF THE STEERING RIDGE, WITH LANDFALL EXPECTED WITHIN THE NEXT 12 HOURS IN THE VICINITY OF KUAKATA, BANGLADESH. NO SIGNIFICANT CHANGE IN THE INTENSITY ARE EXPECTED, WITH LANDFALL AT OR NEAR 40 KNOTS. AFTER LANDFALL, THE SYSTEM WILL TRACK GENERALLY WEST-NORTHWEST WHILE SLOWLY WEAKENING DUE TO LAND INTERACTION, BEFORE DISSIPATING OVER EASTERN INDIA NO LATER THAN TAU 36.

MODEL DISCUSSION: AVAILABLE TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD, PROVIDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT, THOUGH THE JTWC FORECAST DEVIATES ABOUT FIVE KNOTS HIGHER IN THE FIRST 12 HOURS, BUT OTHERWISE ALIGNS WELL WITH THE GUIDANCE PACKAGE, WITH HIGH CONFIDENCE.