Western Pacific: congested cyclonic traffic! 07/03utc updates

JTWC ARE ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON 13W, 14W, 15W. INVEST 91W WAS UP-GRADED TO MEDIUM AT 06/2030UTC.

TS 13W(LUPIT). WARNING 18 ISSUED AT 07/03UTC.THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM 13W (LUPIT) TOOK A TEMPORARY JOG TOWARD THE SOUTHEAST BUT HAS RESUMED AN EAST-NORTHEASTWARD TRAJECTORY AS IT MAKES LANDFALL OVER NORTHERN TAIWAN. THE SYSTEM IS FORECAST TO HEAVILY INTERACT WITH THE COMPLEX TERRAIN OF TAIWAN OVER THE NEXT 6 TO 12 HOURS, SO THERE IS LOW CONFIDENCE IN THE SHORT-TERM TRACK AND INTENSITY FORECASTS. THE SOUTHWESTERLY MONSOON FLOW IS SPLIT TO THE WEST AND EAST OF TAIWAN, WITH THE LATTER REGION CONTINUING TO EXHIBIT SOME EVIDENCE OF LEE SURFACE TROUGH FORMATION TO THE NORTHEAST OF TAIWAN, WHICH COULD IMPACT THE TRACK AND REDEVELOPMENT OF THE LLCC ONCE IT EXITS BACK OVER OPEN WATER EAST- NORTHEAST OF TAIPEI. BETWEEN 12H AND 36H, LUPIT IS FORECAST TO TRACK NORTHEASTWARD TOWARD KYUSHU AND WILL BE LOCATED TO THE NORTHWEST OF OKINAWA, JAPAN AROUND 24-30H. THE TIMING AND POSITION OF THE TRACK WILL DEPEND UPON THE REORGANIZATION OF THE LLCC ONCE THE SYSTEM CROSSES THE LONGITUDE OF THE TAIWAN CENTRAL MOUNTAIN RANGE. INTENSIFICATION TO A PEAK INTENSITY OF AROUND 50 KNOTS IS EXPECTED PRIOR TO LANDFALL IN KYUSHU. EXTRATROPICAL TRANSITION SHOULD BEGIN AS LUPIT CROSSES HONSHU, WITH TRANSITION COMPLETE BY 96H UPON EXITING JAPAN.

TS 13W(LUPIT).SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD CIRCULATION BEGINNING TO BECOME DEFORMED BY THE HIGH TERRAIN OF TAIWAN, WITH THE ONSHORE FLOW TO THE SOUTH OF THE LOW-LEVEL CIRCULATION CENTER (LLCC) GENERATING A BAND OF DEEP CONVECTION. THE INITIAL POSITION WAS PLACED WITH MEDIUM CONFIDENCE BASED ON A 062237UTC SSMIS 91GHZ MICROWAVE IMAGE AND RADAR, INDICATING THAT THE LLCC HAD TAKEN A TEMPORARY JOG TOWARD THE SOUTHEAST WITH A TURN BACK TOWARD THE EAST-NORTHEAST OVER THE LAST 6 HOURS. THE INITIAL INTENSITY IS HELD AT 40 KNOTS BASED ON NO CHANGE TO THE DVORAK ASSESSMENTS FROM PGTW AND RJTD OVER THE LAST 6 HOURS.

TS 13W(LUPIT). MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN GOOD AGREEMENT, WITH ONLY A SLIGHT WESTWARD SHIFT AFTER THE SYSTEM REDEVELOPS NORTHEAST OF TAIWAN. THE CONSENSUS MEMBERS ARE TIGHTLY CLUSTERED, WITH ONLY A 130 KM SPREAD AT 72H. THE FORECAST TRACK FOLLOWS THE PREVIOUS WARNING CLOSELY, WITH THE GREATEST UNCERTAINTY ASSOCIATED WITH THE ALONG-TRACK ERRORS AS LUPIT ACCELERATES TOWARD THE NORTHEAST DURING ITS EAST CHINA SEA TRANSIT. THE LARGE-SCALE SYNOPTIC PATTERN RENDERS MEDIUM CONFIDENCE TO THE TRACK FORECAST BEYOND 72 HOURS, WITH LOW CONFIDENCE IN THE NEAR TERM AS LUPIT INTERACTS WITH THE TERRAIN OF TAIWAN. THE INTENSITY FORECAST LIKEWISE FOLLOWS CONSENSUS. BOTH HWRF AND COAMPS-TC HAVE BACKED OFF A BIT ON THEIR FORECAST PEAK INTENSITY, WITH THE SYSTEM MOSTLY LIKELY STAYING BELOW TYPHOON INTENSITY. AT THIS TIME, THERE IS NOT ENOUGH CERTAINTY IN WHAT WILL REMAIN OF THE LLCC AFTER INTERACTION WITH TAIWAN, SO THE REINTENSIFICATION FORECAST REMAINS CONSERVATIVE. MUCH WILL DEPEND UPON THE EXTENT TO WHICH THE INNER CORE OF LUPIT WILL REMAIN INTACT OVER THE NEXT 24 HOURS.

TS 14W(MIRINAE). WARNING 12 ISSUED AT 07/03UTC.THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM 14W (MIRINAE) CONTINUES TO TRACK TOWARD THE NORTHEAST. THE MAJOR SHORTWAVE TROUGH TO THE WEST HAS DEGRADED STRUCTURE, AND DRIER AIR HAS WRAPPED INSIDE THE SYSTEM. THE SYSTEM IS FORECAST TO ACCELERATE NORTHEASTWARD THROUGH 24H, THEN TURN EASTWARD BY 36H AS IT MERGES INTO THE STRONG EAST-WEST ORIENTED BAROCLINIC ZONE NEAR THE 38TH PARALLEL. THEREAFTER, THE SYSTEM WILL ENCOUNTER COOLER SSTS AND VERTICAL WIND SHEAR WILL BEGIN TO DOMINATE THE OUTFLOW ALOFT, LEADING TO STEADY WEAKENING THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE SYSTEM IS EXPECTED TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY 72H AND, AS IT MOVES UNDER STRONG MID- LATITUDE WESTERLIES AND DEVELOPS FRONTAL CHARACTERISTICS, WILL COMPLETE ETT NO LATER THAN 96H.

TS 14W(MIRINAE). SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH TIGHT BANDING WRAPPING INTO THE LLCC FROM THE SOUTHERN AND EASTERN PERIPHERIES. FURTHER ANALYSIS INDICATES DEEP FLARING CONVECTION IN THE NORTHWEST QUADRANT. A BULLSEYE 070014UTC METOP-B ASCATT PASS SHOWS A WELL DEFINED CENTER WITH A 40-45 KNOT WIND FIELD TO THE SOUTHEAST OF THE LLCC. THE INITIAL POSITION AND INITIAL INTENSITY OF 45 KNOTS ARE ASSESSED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED MSI AND ASCAT DATA.

TS 14W(MIRINAE).MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A 150 KM SPREAD AT 36H, INCREASING TO 260 KM SPREAD BY 96H, LENDING OVERALL HIGH CONFIDENCE IN THE FORECAST TRACK THROUGH 72H AND MEDIUM CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS SPREAD BY APPROXIMATELY 20 KNOTS BY 48H, WITH THE COAMPS-TC INDICATING A PEAK INTENSITY OF TYPHOON STRENGTH AS THE OUTLIER. THE JTWC FORECAST IS HEDGED SLIGHTLY ABOVE THE INTENSITY CONSENSUS WITH MEDIUM CONFIDENCE.

TS 15W(NIDA). WARNING 11 ISSUED AT 07/03UTC.THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM 15W (NIDA) HAS ACCELERATED EAST- NORTHEASTWARD OVER THE PAST 6 HOURS ALONG THE NORTHERN PERIPHERY OF THE DEEP SUBTROPICAL RIDGE LOCATED TO THE SOUTH. TS 15W IS EXPECTED TO MAINTAIN THIS GENERAL TRACK THROUGHOUT THE FORECAST PERIOD. VERTICAL WIND SHEAR IS FORECAST TO STEADILY INCREASE AS THE SYSTEM APPROACHES THE BAROCLINIC ZONE BY 24H. TS 15W HAS ALREADY MOVED NORTH OF THE 26C ISOTHERM AND INTERACTION WITH THE COOLER WATERS WILL ASSIST IN INITIATING EXTRATROPICAL TRANSITION.

TS 15W(NIDA). SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SLIGHTLY SHEARED, COMPACT SYSTEM WITH PERSISTENT DEEP CONVECTION THAT HAS BEEN DISPLACED TO THE EAST OF THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED MSI AND A PARTIAL 070010UTC METOP-B ASCAT PASS. THE INITIAL INTENSITY OF 55 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE HEDGED HIGHER THAN THE PGTW DVORAK ESTIMATE AND LOWER THAN THE MORE AGGRESSIVE ADT AND SATCON ESTIMATES.

TS 15W(NIDA). MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT WITH MINIMAL SPREAD OF 130 KM AT 36H. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST WITH HIGH CONFIDENCE AND SLIGHTLY AHEAD OF THE CONSENSUS BASED ON RECENT ACCELERATION. SIMILARLY, THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH ALL MODELS INDICATING A SHORT PERIOD OF CONSTANT INTENSITY FOLLOWED BY STEADY WEAKENING. THE JTWC FORECAST FOLLOWS THE BULK OF THE GUIDANCE WITH HIGH CONFIDENCE.

07/06UTC. INVEST 91W. THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED NEAR 32N 146.4E IS NOW LOCATED NEAR 33.6N 147.2E, APPROXIMATELY 715 KM EAST-SOUTHEAST OF TOKYO, JAPAN. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) AND A 070259UTC AMSR2 36GHZ IMAGE DEPICT A CONSOLIDATING LOW-LEVEL CIRCULATION (LLC) WITH CONVECTION BEING SHEARED TOWARD THE EAST. UPPER-LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH WEAK POLWARD OUTLOW AND WARM SEA SURFACE TEMPERATURES OF 28 TO 29C, OFFSET BY CONVERGENCE ON THE WESTERN BOUNDARY AND STRONG VERTICAL WIND SHEAR (20 TO 30 KNOTS). GLOBAL MODELS ARE IN AGREEMENT THAT THE SYSTEM WILL TRACK TO THE NORTHEAST. HOWEVER, THEY ARE SPLIT ON WHETHER 91W WILL CONSOLIDATE AND INTENSIFY TO WARNING CRITERIA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1007 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS MEDIUM.

TS 13W,TS 14W AND TS 15W. KML MAPS AT 07/03UTC.

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