Advisories

WDPN32 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (CHAMPI) WARNING NR 032//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.9N 125.4E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 361 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 43 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPANSIVE 
SYSTEM, WITH A 25NM WIDE, CLOUD-FILLED EYE WITH MULTIPLE MESOVORTICES 
EVIDENT ROTATING AROUND THE INNER EDGE OF THE EYEWALL. EYE 
TEMPERATURES REMAIN ABOVE 13C, THOUGH CLOUD-TOP TEMPERATURES HAVE 
WARMED CONSIDERABLY SINCE 0000Z, NOW MEASURED AT -53C. ANIMATED WATER 
VAPOR IMAGERY AND ATMOSPHERIC MOTION VECTOR ANALYSIS REVEAL ROBUST 
RADIAL OUTFLOW SUPERIMPOSED ON TYPHOON 29W, COUPLED WITH AN ENHANCED 
POLEWARD OUTFLOW CHANNEL SUPPORTED BY A MESOSCALE ANTICYCLONE ALOFT 
JUST EAST OF THE SYSTEM. A 220510Z PARTIAL AMSR3 89GHZ MICROWAVE 
IMAGE REVEALED A FRAGMENTED INNER EYEWALL, OPEN ALONG THE SOUTHWESTERN 
FLANK, A DISTINCT MOAT FEATURE, AND A NASCENT SECONDARY EYEWALL THAT 
IS PARTICULARLY EVIDENT IN THE EASTERN SEMICIRCLE OF THE INNER CORE, 
ROUGHLY DOUBLE THE SIZE OF THE INNER EYEWALL. SURFACE OBSERVATIONS 
FROM THE SOUTHWESTERN RYUKYU ISLANDS AND SOUTHEASTERN TAIWAN EXCEEDING 
35 KNOTS SUPPORT THE INITIAL WIND RADII ASSESSMENT WITH HIGH 
CONFIDENCE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE 
BASED ON THE EYE FEATURE IN BOTH THE MSI AND THE AMSR3 IMAGERY. THE 
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON A BLEND 
OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES BELOW. 
ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE OVERALL, WITH WARM SSTS, 
ROBUST OUTFLOW ALOFT, AND LOW DEEP-LAYER VERTICAL WIND SHEAR (VWS). 
HOWEVER, THE ONSET OF YET ANOTHER EYEWALL REPLACEMENT CYCLE (ERC), 
CONCURRENT WITH THE UPWELLING OF SLIGHTLY COOLER OCEANIC WATERS, HAS 
RESULTED IN A MARGINALLY LESS FAVORABLE ENVIRONMENT AND A CONTINUED 
WEAKENING TREND.

INITIAL WIND RADII BASIS: PERSISTENCE AND SURFACE OBSERVATIONS. 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.5 - 127 KTS
   RCTP: T6.0 - 115 KTS
   CIMSS SATCON: 123 KTS AT 220710Z
   CIMSS ADT: 104 KTS AT 220540Z
   CIMSS AIDT: 94 KTS AT 220540Z
   CIMSS D-MINT: 110 KTS AT 220514Z
   CIMSS D-PRINT: 102 KTS AT 220640Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: EYEWALL REPLACEMENT CYCLE. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON (TY) 29W IS CONTINUING TO DECELERATE AS 
IT MOVES DIRECTLY SOUTH OF A MARKED COL REGION OVER THE EASTERN COAST 
OF CHINA AND THE WESTERN EAST CHINA SEA (ECS). AS IT ENTERS THIS 
WEAKENED STEERING PATTERN, AND ESPECIALLY IN LIGHT OF THE IMMINENT 
SECONDARY ERC, THE SYSTEM IS FORECAST TO BOTH SLOW DOWN AND EXHIBIT 
TROCHOIDAL WOBBLE. WHILE THIS TROCHOIDAL MOTION WILL RESULT IN SHORT-
DURATION, ERRATIC TRACK EXCURSIONS, THE OVERALL FORECAST TRACK WILL 
REMAIN NORTHWESTWARD, GRADUALLY TURNING NORTHWARD THROUGH TAU 36. BY 
TAU 36, TY 29W WILL REACH THE STEERING AXIS OF THE STR AND BEGIN TO 
ACCELERATE POLEWARD. BY TAU 48, THE NORTHWESTERN FLANK OF THE STR 
WILL BEGIN TO ERODE DUE TO THE PASSAGE OF A MAJOR SHORTWAVE TROUGH, 
ALLOWING TY 29W TO TURN QUICKLY NORTHEASTWARD THROUGH THE REMAINDER 
OF THE FORECAST PERIOD. LANDFALL ALONG THE SOUTHWESTERN COAST OF 
KYUSHU IS EXPECTED SHORTLY AFTER TAU 72, WITH THE SYSTEM SKIRTING THE 
SOUTHERN COAST OF SHIKOKU THROUGH TAU 96. REGARDING INTENSITY, THE 
COMBINATION OF TRANSLATIONAL DECELERATION-INDUCED UPWELLING OF COOLER 
WATERS AND AN ONGOING ERC, WHICH IS UNLIKELY TO FULLY RESOLVE, WILL 
STEADILY WEAKEN THE SYSTEM OVER THE NEXT 12 HOURS. TY 29W WILL THEN 
MOVE INTO A DEEPER POOL OF ELEVATED OCEAN HEAT CONTENT (OHC) WATERS 
SITUATED SOUTH AND SOUTHWEST OF ISHIGAKIJIMA. AS TY 29W MOVES OVER 
THIS DEEP POOL OF HIGH OHC WATERS BETWEEN TAU 12 AND TAU 24, IT WILL 
TEMPORARILY ARREST ITS WEAKENING TREND. AS THE SYSTEM MOVES INTO THE 
SOUTHERN ECS, HOWEVER, IT WILL RESUME WEAKENING AS IT TRACKS OVER 
STEADILY DECREASING SSTS, COUPLED WITH RAPIDLY INCREASING VERTICAL 
WIND SHEAR AND DRY AIR INTRUSION INTO THE CORE. BY THE TIME THE 
SYSTEM REACHES KYUSHU, IT WILL BE RAPIDLY WEAKENING AND MAY 
POTENTIALLY HAVE DISSIPATED PRIOR TO LANDFALL. ASSUMING THE SYSTEM 
REMAINS INTACT, IT WILL BE RAPIDLY DISRUPTED BY INTENSE UPPER-LEVEL 
SHEAR AND OROGRAPHIC LAND INTERACTION. SIMULTANEOUSLY, BY TAU 72, TY 
29W WILL INITIATE EXTRATROPICAL TRANSITION (ETT) AS IT BEGINS TO 
PHASE WITH A MAJOR 500MB SHORTWAVE TROUGH APPROACHING FROM THE WEST. 
BY TAU 96, TY 29W WILL HAVE TRANSITIONED TO A BAROCLINIC 
EXTRATROPICAL LOW, IF IT HAS NOT DISSIPATED PRIOR. 

MODEL DISCUSSION: TRACK GUIDANCE, WHILE REMAINING BIFURCATED, IS 
STEADILY COMING INTO CLOSER AGREEMENT. THE DATA-DRIVEN MACHINE 
LEARNING (AI) MODELS CONTINUE TO HOLD FAST ON A FASTER RECURVE, 
MAINTAINING THE CORE WELL OFFSHORE OF TAIWAN, RECURVING THROUGH THE 
CENTRAL ECS, AND THEN MAKING LANDFALL ON KYUSHU. THE DYNAMICAL MODELS 
ALSO INDICATE RECURVATURE BUT DEPICT A MORE GRADUAL TRACK, CLIPPING 
THE NORTHEASTERN TIP OF TAIWAN AND THE FAR EASTERN TIP OF COASTAL 
CHINA BEFORE TURNING INTO THE TSUSHIMA STRAIT. THE OTHER MAIN POINT 
OF CONTENTION IS ALONG-TRACK SPEED AFTER RECURVATURE. EVEN AMONG THE 
AI MODELS, THIS SPREAD IS SIGNIFICANT, WITH THE OPERATIONAL GOOGLE 
DEEPMIND (GDM) LOSING THE VORTEX SOUTH OF SASEBO BY TAU 96, WHILE THE 
AI CONSENSUS (AICN) RACES AHEAD BY NEARLY 400NM. SIMILAR ALONG-TRACK 
SPREAD IS APPARENT BETWEEN THE DYNAMICAL AND AI MODELS AT TAU 96. THE 
JTWC FORECAST REMAINS CONSISTENT WITH EARLIER FORECASTS AND IS 
POSITIONED NEAR THE AI CONSENSUS MEAN, WITH HIGH CONFIDENCE. 
INTENSITY GUIDANCE IS IN GOOD OVERALL AGREEMENT. HAFS-A AND HWRF 
DEPICT THE TEMPORARY ARREST OF THE WEAKENING TREND WELL, MAINTAINING 
AN INTENSITY OF 95 KNOTS FROM TAU 12 TO TAU 24, BEFORE RAPIDLY 
WEAKENING THE SYSTEM AFTER TAU 24 AND REJOINING THE REMAINDER OF THE 
GUIDANCE BY TAU 36. THE JTWC FORECAST IS PLACED NEAR THE HAFS-A MODEL 
THROUGH TAU 24, THEN ALIGNS WITH THE MULTI-MODEL CONSENSUS MEAN 
THEREAFTER, WITH MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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