09W(SAOLA) peaks at Super Typhoon Intensity//10W(HAIKUI) to reach Typhoon Intensity by 48h//11W intensifying next 24h//3009utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON 09W(SAOLA), 10W(HAIKUI) AND 11W.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: SUPER TYPHOON (STY) 09W (SAOLA) CONTINUES TO DEFY THE ODDS, HAVING MAINTAINED A STEADY 135 KNOT INTENSITY OVER THE PAST 18 HOURS IN THE FACE OF PERSISTENT, MODERATE EASTERLY SHEAR. ANIMATED ENHANCED INFRARED (EIR) IMAGERY INDICATED THAT THE CLOUD TOP TEMPERATURES WARMED BY ABOUT 10C BETWEEN 0000Z AND 0300Z, BUT THEY HAVE SINCE RECOVERED WHILE THE EYE TEMPERATURE REMAINS ABOVE 15C. ANIMATED VISIBLE IMAGERY SHOWS A STADIUM EYE APPROXIMATELY 18NM WIDE, CONFIRMED BY ANALYSIS OF TAIWAN RADAR DATA. A 300517Z AMSR2 89GHZ MICROWAVE IMAGE REVEALS A WELL-DEFINED INNER EYEWALL WITH A CLEAR SECONDARY EYEWALL BEGINNING TO FORM UP AROUND 40-50NM OUT FROM THE CENTER, AND IS CONFIRMED BY THE SAME FEATURE SEEN IN THE RADAR DATA. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE VISIBLE, INFRARED, RADAR AND AMSR2 DATA. THE INITIAL INTENSITY REMAINS SET AT 135 KNOTS, CONSISTENT WITH THE BULK OF THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES AS WELL AS THE SUBJECTIVE ESTIMATES SUCH AS ADT, AIDT, DPRINT AND DMINT, ALL OF WHICH FALL IN THE RANGE OF 129-135 KNOTS. ADDITIONALLY, AN EARLIER 292156Z RCM-3 SAR PASS SHOWED A MAXIMUM WIND OF 136 KNOTS IN THE SOUTHWESTERN QUADRANT, PROVIDING ADDITIONAL CONFIDENCE IN INTENSITY TRENDS. THE SYSTEM CONTINUES TO TRACK WEST-NORTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF AN EXTENSION OF THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. CONDITIONS REMAIN GENERALLY FAVORABLE WITH WARM SSTS, AND GOOD RADIAL OUTFLOW WHICH IS ABLE TO PUSH BACK ON THE MODERATE EASTERLY SHEAR.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: STY 09W WILL CONTINUE TRACKING WEST-NORTHWEST THROUGH TAU 48 UNDER THE INFLUENCE OF THE STR TO THE NORTHEAST. A COMBINATION OF FACTORS, INCLUDING THE TRACK OF TROPICAL STORM 10W SOUTH OF OKINAWA AND THE PASSAGE OF A STRONG MID-LATITUDE TROUGH TO THE NORTH, WILL ERODE THE STEERING RIDGE, LOOSEN THE STEERING GRADIENT AND LEAD TO A SLOW-DOWN IN THE TRACK SPEED AFTER TAU 24. IN THE LEE OF THE TROUGH PASSING BY TO THE NORTH, AND TRANSIENT DEEP-LAYER ANTICYCLONE WILL BUILD IN TO THE WEST OF SHANGHAI, AND PUSH STY 09W ONTO A MORE WESTWARD TRACK THROUGH TAU 72. THE SYSTEM IS EXPECTED TO PASS VERY CLOSE TO HONG KONG BUT REMAIN OFFSHORE THROUGH THE FORECAST PERIOD. AFTER TAU 72, THE TRANSIENT ANTICYCLONE IS ABSORBED INTO THE LARGER STR TO THE NORTHEAST AND THE STEERING FLOW QUICKLY WEAKENS, LEAVING STY 09W WITHOUT MUCH STEERING INFLUENCE, AND THE SYSTEM WILL BECOME QUASI-STATIONARY BY THE END OF THE FORECAST. IN TERMS OF INTENSITY, WITH CLEAR EVIDENCE EMERGING OF A SECONDARY EYEWALL, THE ONSET OF AN EYEWALL REPLACEMENT CYCLE (EWRC) IS IMMINENT IF NOT ALREADY OCCURRING. THUS, THE SYSTEM IS EXPECTED TO SLOWLY WEAKEN THROUGH THE NEXT 24 HOURS. THE EXACT AMOUNT OF WEAKENING AND HOW LONG IT MAY TAKE FOR THE EWRC TO COMPLETE ARE UNKNOWN BUT CURRENTLY EXPECTED TO WRAP UP BY AROUND TAU 24. THE SYSTEM WILL BY THEN BE TAPPING INTO THE DIFFLUENT EASTERN SIDE OF THE DEEP TROUGH MOVING BY TO THE NORTH, ALLOWING FOR A SHARP INCREASE IN POLEWARD OUTFLOW. THIS SHOULD ALLOW THE SYSTEM TO MAINTAIN INTENSITY OR EVEN INTENSIFY SLIGHTLY UP THROUGH TAU 36. THEREAFTER AS THE SYSTEM APPROACHES THE COAST OF SOUTHEAST CHINA, SOUTHERLY SHEAR WILL RAPIDLY INCREASE. COMBINED WITH A REDUCTION IN SSTS, INGESTION OF DRY CONTINENTAL AIR INTO THE CORE AND DISRUPTION OF THE LOW-LEVEL INFLOW AS IT TRACKS SOUTH OF HONG KONG, THE SYSTEM WILL RAPIDLY WEAKEN TO JUST 50 KNOTS BY THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT OVER THE PAST COUPLE OF MODEL RUNS, WITH NEARLY ALL OF THE CONSENSUS MEMBERS NOW AGREEING ON AN ARCING TRACK THAT REMAINS OFFSHORE AND RUNS PARALLEL TO THE CHINESE COAST AFTER TAU 48. THE LATEST ECMWF AND EGRR TRACKERS ARE THE ONLY OUTLIERS ON THE NORTHERN SIDE OF THE ENVELOPE WHICH SHOW A LANDFALL IN THE VICINITY OF HONG KONG AROUND TAU 48, THEN TRACK THE SYSTEM ALONG THE COASTLINE THROUGH THE REMAINDER OF THE FORECAST. THE JTWC FORECAST LIES JUST SOUTH OF THE CONSENSUS MEAN, AND JUST NORTH OF THE GFS DETERMINISTIC AND ENSEMBLE MEAN TRACKERS. CONFIDENCE IS HIGH OVERALL, BUT VERY SMALL DEVIATIONS OR WOBBLES IN THE CENTER OF THE SYSTEM, ESPECIALLY AS IT UNDERGOES EYEWALL REPLACEMENT COULD LEAD TO A SHIFT IN THE FORECAST TRACK OVER LAND. INTENSITY GUIDANCE IS IN GOOD AGREEMENT OVERALL, THOUGH THE HAFS-A TAKES THE SYSTEM INLAND WELL EAST OF HONG KONG AND THUS MUST BE DISCOUNTED FROM THE INTENSITY CONSENSUS. THE CTCX IS CLOSEST THE JTWC FORECAST, SHOWING A WEAKENING PHASE DUE TO THE EWRC FOLLOWED BY A BRIEF RECOVERY BEFORE SHARP WEAKENING AFTER TAU 48. THE VAGARIES ASSOCIATED WITH THE EWRC, SUCH AS THE LENGTH OF THE CYCLE AND THE ULTIMATE LOW POINT IN THE INTENSITY GENERATE MEDIUM TO LOW CONFIDENCE IN THE INTENSITY FORECAST.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS THE PREVIOUSLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) HAS MOVED ONCE MORE UNDER AN AREA OF DEEP CONVECTION AND IS NOW OBSCURED. VORTICAL HOT TOWERS CONTINUE TO FIRE ALONG THE SOUTHERN SIDE OF THE TILTED VORTEX BUT HAVE YET TO BE ABLE TO ROTATE UPSHEAR, AND HENCE THE SYSTEM HAS YET TO INTENSIFY. A LACK OF RECENT MICROWAVE IMAGERY MAKES ANALYSIS OF THE VORTEX TILT AND THE INITIAL POSITION A LOW CONFIDENCE AFFAIR. REANALYSIS OF PREVIOUS INTENSITY DATA INCLUDING A 292116Z SMAP PASS RESULTED IN A DOWNGRADE OF THE INTENSITY OF BOTH THE 291800Z AND 300000Z INTENSITIES TO 45 KNOTS. THE INITIAL POSITION REMAINS SET AT 45 KNOTS, WITH MEDIUM CONFIDENCE, HEDGED LOWER THAN THE AGENCY CURRENT INTENSITY ESTIMATES BASED ON THE EARLIER SMAP DATA, AS WELL AS A T3.0 ADT, 42 KNOT AIDT, AND SATCON OF 48 KNOTS. THE SYSTEM IS MOVING TOWARDS THE NORTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE WITH WARM SSTS, MODERATE EQUATORWARD OUTFLOW AND A DEVELOPING POLEWARD OUTFLOW CHANNEL TEMPERED BY LOW TO MODERATE NORTHERLY WIND SHEAR.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM (TS) 10W (HAIKUI) IS FORECAST TO CONTINUE TRACKING WEST-NORTHWEST ALONG THE SOUTHWEST SIDE OF THE STEERING RIDGE THROUGH THE BULK OF THE FORECAST PERIOD. GLOBAL MODEL FIELDS HAVE COME INTO MUCH BETTER AGREEMENT ON THE EVOLUTION OF THE UPPER-LEVEL PATTERN OVER THE LAST COUPLE OF RUNS, PROVIDING INCREASED CONFIDENCE IN THE TRACK GUIDANCE. OVER THE COURSE OF THE FIRST 72 HOURS OF THE FORECAST, THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST IS EXPECTED TO EXTEND SOUTHWESTWARD, WITH A SHARP RIDGE AXIS DEVELOPING ALONG A LINE EXTENDING FROM WEST OF SHANGHAI TO TOKYO. THIS WILL SERVE TO KEEP THE TRACK OF 10W ON A MORE DEPRESSED TRAJECTORY, PASSING SOUTH OF OKINAWA AROUND TAU 48 AND MOVING INTO THE EAST CHINA SEA. AFTER TAU 72, THE MODELS DO BEGIN TO DIVERGE ON HOW THEY HANDLE A SHARP MID-LATITUDE TROUGH MOVING EAST OUT OF MONGOLIA; HOW DEEP WILL IT BE AND HOW FAST WILL IT ERODE THE RIDGE. THE GFS AND NAVGEM MODELS SHOW A WEAKER TROUGH, WHICH DOES NOT BREAK DOWN THE RIDGE AS MUCH, FORCING THE SYSTEM ONTO A FLATTER TRACK, MAKING LANDFALL IN THE VICINITY OF WENZHOU, CHINA BY TAU 96. THE ECMWF ON THE OTHER HAND, AND THE GFS ENSEMBLE INTERESTINGLY ENOUGH, SHOW A STRONGER TROUGH WHICH ERODES THE RIDGE ALLOWING THE SYSTEM TO RECURVE NORTH TOWARDS SHANGHAI BY TAU 120. CURRENT ASSESSMENT OF THE GLOBAL MODEL FIELDS SUGGESTS THE ECMWF SOLUTION MAY BE THE BETTER OPTION, AT LEAST FOR THE MOMENT IF FOR NO OTHER REASON THAN ITS CONSISTENCY OVER THE PAST 48 HOURS WHEREAS THE GFS HAS BEEN EXHIBITING GIGANTIC SWINGS FROM RUN TO RUN. THE JTWC FORECAST TAKES THE SYSTEM INLAND SOUTH OF SHANGHAI AROUND TAU 96 THEN TRACKS NORTHWARD ACROSS EASTERN CHINA THROUGH TAU 120. IN TERMS OF INTENSITY, THE SYSTEM WILL CONTINUE TO STRUGGLE FOR THE NEXT 48 HOURS AS IT CONTINUES TO BE CONSTRAINED BY VORTEX TILT AND MODERATE SHEAR. BY AROUND TAU 48, THE SHEAR IS EXPECTED TO BACK OFF SIGNIFICANTLY, WHICH SHOULD ALLOW THE VORTEX TO SYMMETRIZE AND START A PERIOD OF RAPID INTENSIFICATION AS THE SYSTEM PASSES SOUTH OF OKINAWA AND INTO THE EAST CHINA SEA. LAND INTERACTION WILL LEAD TO RAPID WEAKENING AFTER LANDFALL.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT WITH THIS RUN, WITH EVEN THE GFS GIVING UP ON THE ERRATIC TRACK THAT IT WAS DEPICTING OVER THE PAST 36 HOURS. ALL CONSENSUS MEMBERS NOW AGREE ON A WEST-NORTHWEST TRACK THROUGH TAU 48 BUT DO SHOW SOME DIVERGENCE AFTER THIS POINT AS DESCRIBED ABOVE. THE HAFS-A AND COAMPS-TC, WHILE NOT MEMBERS OF THE TRACK CONSENSUS, SHOULD BE NOTED AS BEING SOUTHWARD OUTLIERS, TAKING THE SYSTEM OVER NORTHERN TAIWAN OR JUST NORTHEAST OF TAIWAN BY THE END OF THE FORECAST. THE GFS TRACKS JUST NORTH OF MIYAKOJIMA WHILE THE ECMWF HAS SHIFTED A BIT SOUTH AND NOW KEEPS THE TRACK SOUTH OF OKINAWA BY ABOUT 25NM. THE RESULT IS A TIGHTENING OF THE GUIDANCE ENVELOPE THOUGH TAU 48. AFTER THIS POINT TWO GROUPS EMERGE, WITH THE NAVGEM, GFS AND UKMET ENSEMBLE TRACKING THE SYSTEM INTO CHINA NEAR WENZHOU WHILE THE ECMWF, ECENS, AND GEFS TURN THE SYSTEM POLEWARD TOWARDS SHANGHAI. THE JTWC FORECAST LIES CLOSE TO THE CONSENSUS MEAN AND THE ECMWF TRACK WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS FOR THE MOST PART IN GOOD AGREEMENT ON A SLOW INTENSIFICATION TREND TO TAU 48 FOLLOWED BY A SHARP INTENSIFICATION PERIOD THROUGH TAU 72 AND THEN RAPID WEAKENING AFTER LANDFALL. THE JTWC FORECAST IS CONSISTENT WITH THE INTENSITY CONSENSUS MEAN AND THE COAMPS-TC FORECAST.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS OF PERSISTENT DEEP CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 300531Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTS CONVECTIVE BANDING WRAPPING INTO AN ELONGATED LOW-LEVEL CIRCULATION (LLC). ANIMATED WATER VAPOR IMAGERY DEPICTS A MODERATE POLEWARD OUTFLOW CHANNEL ENHANCED BY AN UPPER-LEVEL LOW TO THE NORTHEAST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE SSMIS IMAGE IN COMBINATION WITH AGENCY DVORAK POSITION FIXES. A 300336Z AMSR2 WINDSPEED IMAGE SHOWS A 30-35 KNOTS SWATH ON THE NORTHERN SEMICIRCLE. THE INITIAL INTENSITY OF 35 KNOTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AMSR2 WINDSPEED IMAGE, RECENT ASCAT IMAGERY AND AGENCY DVORAK INTENSITY ESTIMATES. ENVIRONMENTAL CONDITIONS ARE FAVORABLE WITH MODERATE EQUATORWARD OUTFLOW, IMPROVING POLEWARD OUTFLOW INTO A UPPER-LEVEL LOW POSITION TO THE NORTHEAST, AND LOW VERTICAL WIND SHEAR.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM 11W IS FORECAST TO TRACK NORTHWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST THROUGH TAU 12. THE STR IS EXPECTED TO STRENGTHEN TO THE NORTHEAST AND EXTEND TO THE WEST, WHICH WILL TURN THE SYSTEM NORTHWESTWARD, INITIALLY, THEN WEST-NORTHWESTWARD THROUGH TAU 120. IN TERMS OF INTENSITY, 11W IS EXPECTED TO STEADLY INTENSIFY THROUGH TAU 24, AS A UPPER-LEVEL LOW TO THE NORTH SHIFTS WESTWARD WHICH WILL PROVIDE ENHANCED POLEWARD OUTFLOW. HOWEVER, AFTER TAU 36, OUTFLOW BECOMES LESS FAVORABLE WHILE VERTICAL WIND SHEAR (VWS), AND DRY AIR ENTRAINMENT INCREASE RESULTING IN A GRADUAL WEAKENING TREND.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72 WITH ONLY A 115NM SPREAD IN THE SOLUTIONS. AFTER TAU 72, THE CROSS-TRACK SPREAD INCREASES TO 347 NM BY TAU 120, SPANNING FROM AMAMI OSHIMA TO KYOTO. OVERALL, THE JTWC FORECAST TRACK FOLLOWS CLOSE TO THE MULTI-MODEL CONSENSUS AND IS PLACED WITH HIGH CONFIDENCE THROUGH TAU 72, WITH MEDIUM CONFIDENCE THEREAFTER. THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT AND SUPPORTS A STEADY INTENSIFICATION PHASE, WITH RAPID INTENSIFICATION (RI) GUIDANCE TRIGGERED OVER THE NEXT 24-36 HOURS. AFTER TAU 36, ASIDE FROM COAMPS-TC, WHICH SHOWS A GRADUAL DECREASE IN INTENSITY, THE BULK OF THE INTENSITY GUIDANCE SHOWS A STEADY WEAKENING TREND THROUGHOUT THE FORECAST PERIOD. OVERALL, THE JTWC INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE THROUGHOUT THE FORECAST PERIOD.