Advisories

WDPN32 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (CHAMPI) WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.7N 123.4E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 292 NM SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A CONTRACTING
AND WARMING EYE SURROUNDED BY RAPIDLY COOLING, INCREASINGLY SYMMETRIC 
CLOUD TOPS, INDICATIVE OF AN INTENSIFYING TYPHOON (TY). TY 29W 
ENTERED A POOL OF HIGH OCEANIC HEAT CONTENT (OHC) AROUND 222100Z 
AND LEVERAGED THE ENHANCED SURFACE ENTHALPY FLUXES TO RAPIDLY 
ORGANIZE AND RE-INTENSIFY. ADDITIONALLY, THE SYSTEM HAS ESTABLISHED 
AN EXTREMELY STRONG, DIVERGENT POLEWARD OUTFLOW CHANNEL AUGMENTING 
THE EXISTING RADIAL OUTFLOW OVER THE INNER CORE. THIS SYNERGISTIC 
COMBINATION HAS DRIVEN RAPID RE-INTENSIFICATION OVER THE PAST 6-8 
HOURS. A 230606Z GMI COLOR-ENHANCED 89 GHZ MICROWAVE IMAGE INDICATES 
THAT THE INNER EYEWALL HAS FULLY RE-ESTABLISHED, WITH A REMNANT 
SECONDARY EYEWALL EVIDENT ONLY ALONG THE EASTERN QUADRANT. ANIMATED
RADAR DATA FROM THE CENTRAL WEATHER BUREAU (CWB) IN TAIWAN DEPICTS
RAPID EYE CONTRACTION TO A DIAMETER OF 17-20 NM, A ROBUST INNER 
EYEWALL, AND A SECONDARY OUTER EYEWALL MOST PREVALENT ALONG THE 
EASTERN FLANK. SURFACE OBSERVATIONS FROM YONAGUNI ISLAND AT 230800Z 
INDICATED NORTHEASTERLY WINDS AT 53G76 KTS AND A RAPIDLY FALLING MEAN 
SEA LEVEL PRESSURE (MSLP) OF 959.9 MB. THE EYE OF TY 29W IS EXPECTED 
TO PASS DIRECTLY OVER THE ISLAND WITHIN THE NEXT 1-2 HOURS. THE 
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON CONCURRENT 
RADAR, MICROWAVE, AND MSI DATA. THE INITIAL INTENSITY IS ASSESSED 
WITH MEDIUM CONFIDENCE BASED ON A SYNTHESIS OF THE OBJECTIVE AND 
SUBJECTIVE INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL CONDITIONS 
REMAIN FAVORABLE, CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES 
(SSTS), HIGH OHC, LOW VERTICAL WIND SHEAR (VWS), AND VIGOROUS DUAL-
CHANNEL OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE AND OBJECTIVE BEST TRACK. 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED SOUTHEAST OF HONSHU. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.0 - 90 KTS
   CIMSS SATCON: 111 KTS AT 230515Z
   CIMSS ADT: 109 KTS AT 230540Z
   CIMSS AIDT: 102 KTS AT 230540Z
   CIMSS D-MINT: 98 KTS AT 230606Z
   CIMSS D-PRINT: 98 KTS AT 230600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 29W CONTINUES TO TRACK NORTH-NORTHWESTWARD
ALONG THE WESTERN PERIPHERY OF THE DEEP-LAYER STR TO THE EAST. 
SHORT-TERM TROCHOIDAL WOBBLES ARE ANTICIPATED OVER THE NEXT FEW 
HOURS AS THE SYSTEM CROSSES YONAGUNI ISLAND AND EMERGES INTO THE 
SOUTHERN EAST CHINA SEA (ECS). AS THE SYSTEM REACHES ITS CLOSEST 
POINT OF APPROACH TO NORTHEASTERN TAIWAN, SEVERAL MESOSCALE AND 
GLOBAL MODELS (INCLUDING GFS AND ECMWF) DEPICT TOPOGRAPHIC INTERACTION 
WITH THE ISLANDS CENTRAL MOUNTAIN RANGE, INDUCING A QUASI-STATIONARY 
PERIOD OR CYCLONIC LOOP BETWEEN TAU 12 AND TAU 18. COMPLEX TERRAIN 
INTERACTIONS WITH TAIWAN FREQUENTLY INDUCE ERRATIC MOTION, MAKING 
A SHORT-TERM TRACK DEVIATION POSSIBLE AFTER THE SYSTEM PASSES 
YONAGUNI ISLAND. THE JTWC FORECAST REFLECTS THIS POTENTIAL BY 
DEPICTING A SLIGHTLY MORE NORTHWESTWARD VECTOR AND SHARP DECELERATION 
THROUGH TAU 12. POLEWARD MOTION SHOULD RESUME AFTER TAU 12, FOLLOWED 
BY RAPID NORTHEASTWARD ACCELERATION AFTER TAU 36 AS AN APPROACHING 
MID-LATITUDE TROUGH ERODES THE NORTHWESTERN PERIPHERY OF THE STR 
AND CAPTURES THE SYSTEM IN STRONG SOUTHWESTERLY STEERING FLOW. 
LANDFALL ALONG THE WESTERN COAST OF KYUSHU IS FORECAST AROUND TAU 
72, AFTER WHICH THE SYSTEM WILL RAPIDLY RE-EMERGE OVER THE WESTERN 
PACIFIC, TRACKING SOUTH OF SHIKOKU AND HONSHU THROUGH TAU 96. 
REGARDING INTENSITY, THE SYSTEM HAS REACHED ITS NEAR-TERM PEAK, 
AND AFTER CROSSING YONAGUNI ISLAND, WILL ENCOUNTER SIGNIFICANTLY 
LOWER OHC DESPITE WARM SURFACE WATERS. THE EXPECTED SLOW TRANSLATION 
SPEED WILL ENHANCE OCEANIC UPWELLING AND INNER-CORE MIXING, RAPIDLY 
COOLING UNDERLYING SSTS. CONSEQUENTLY, TY 29W WILL BEGIN A WEAKENING 
TREND, PARTICULARLY AFTER TAU 12. BEYOND TAU 24, ENVIRONMENTAL 
CONDITIONS WILL STEADILY DETERIORATE DUE TO INCREASING WESTERLY 
VWS AND MID-LEVEL DRY AIR ENTRAINMENT. THE SYSTEM WILL INITIATE 
EXTRATROPICAL TRANSITION (ETT) BY TAU 60, UNDERGOING RAPID BAROCLINIC 
TRANSFORMATION AT LANDFALL AND COMPLETING ETT NO LATER THAN TAU 96. 
AS THE SYSTEM TRAVERSES KYUSHU, COMBINED UPPER-LEVEL SHEAR AND 
FRICTIONAL DISRUPTION WILL LIKELY WEAKEN THE SYSTEM BELOW 35 KTS; 
HOWEVER, UPON RE-EMERGING OVER OPEN WATER, ROBUST BAROCLINIC FORCING 
WILL DRIVE POST-TROPICAL RE-INTENSIFICATION. 

MODEL DISCUSSION: NUMERICAL TRACK GUIDANCE IS IN GENERAL AGREEMENT 
ON THE SYNOPTIC EVOLUTION, THOUGH MULTIPLE MODELS DEPICT NEAR-TERM 
BIFURCATION DUE TO TOPOGRAPHIC INTERACTION WITH NORTHERN TAIWAN.
THE PRIMARY MODELS DEPICTING SIGNIFICANT TERRAIN-INDUCED DEVIATIONS 
ARE EC-AIFS, EGRR, HAFS-A, AND HWRF, WITH GFS SHOWING A SIMILAR
EFFECT TO A LESSER DEGREE. ONLY THE MESOSCALE GUIDANCE DEPICTS THE
SYSTEM MAINTAINING A NORTHWESTWARD TRAJECTORY AND DISSIPATING OVER
EASTERN CHINA. OTHER MODELS THAT DEPICT INITIAL ERRATIC MOTION
STILL RESUME A POLEWARD RECURVATURE AFTER TAU 24, WHILE THE REMAINDER 
OF THE CONSENSUS MAINTAINS A STEADY NORTHWESTWARD TRACK INTO THE ECS 
BEFORE RECURVING NORTHEASTWARD. THE ECMWF AND ECMWF ENSEMBLE (ECEPS) 
MEAN ANCHOR THE WESTERN EDGE OF THE TRACK ENVELOPE, WHILE THE DATA-
DRIVEN AI MODELS AND AI CONSENSUS BOUND THE EASTERN EDGE. CROSS-TRACK 
SPREAD INCREASES TO 200 NM BY TAU 96; HOWEVER, ALONG-TRACK TIMING 
SPREAD IS MUCH MORE PRONOUNCED, REACHING 300 NM AT TAU 72 (BETWEEN 
THE SLOWER ECMWF AND FASTER AI CONSENSUS) AND EXPANDING TO NEARLY 
700 NM BETWEEN THE ECEPS AND PROGRESSIVE GFS BY TAU 96. THE JTWC TRACK 
FORECAST IS PLACED NEAR THE OPERATIONAL GOOGLE DEEPMIND (GDM) THROUGH 
TAU 48, TRANSITIONING TO THE AI CONSENSUS THROUGH TAU 96. INTENSITY 
GUIDANCE IS IN GOOD AGREEMENT, DEPICTING A STEADY WEAKENING TREND 
THROUGH TAU 72 FOLLOWED BY STABILIZATION OR SLIGHT BAROCLINIC 
RE-INTENSIFICATION AS THE SYSTEM COMPLETES ETT. THE JTWC INTENSITY 
FORECAST CLOSELY TRACKS THE GDM SOLUTION THROUGH THE FORECAST PERIOD. 

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