Advisories

WDPN32 PGTW 171500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (CHAMPI) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.6N 146.1E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 96 NM SOUTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE OVERALL STRUCTURE OF TY 29W IN ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY HAS DETERIORATED OVER THE PAST SIX HOURS, AS THE
THE PREVIOUSLY CLOUD-FREE, PINHOLE EYE HAS FILLED IN DUE TO AN ONGOING 
EYEWALL REPLACEMENT CYCLE (ERC). THE EYE REMAINS DETECTABLE IN EIR 
IMAGERY, AND APPEARS TO BE SLIGHTLY LARGER THAN SIX HOURS AGO. 
HOWEVER, THE EYE TEMPERATURES ARE VERY COLD (APPROXIMATELY -50C). 
ANIMATED RADAR IMAGERY FROM GUAM SHOWS THAT THE EYE TOOK A A TEMPORARY 
WEST-SOUTHWESTWARD TROCHOIDAL JOG OVER THE PAST SIX HOURS; HOWEVER, 
THE INTEGRATED MOTION VECTOR REMAINS STABLE AT 280 DEGREES AT 14 KNOTS 
BASED ON THE BEST TRACK. OVER THE PAST TWO HOURS, THE SYSTEM HAS 
RESUMED A WEST-NORTHWESTWARD HEADING AMID TROCHOIDAL OSCILLATION. 
RADAR DATA CLEARLY RESOLVES A CONCENTRIC EYEWALL MORPHOLOGY, 
HIGHLIGHTED BY A THICKENING INNER EYEWALL, A DISTINCT RADAR MOAT, AND 
A SECONDARY OUTER EYEWALL SITUATED APPROXIMATELY 30 NM DISTANT FROM 
THE GEOMETRIC CENTER-STRONG STRUCTURAL SIGNATURES CONFIRMING ERC 
PROGRESSION. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE 
BASED ON THE RADAR EYE FIXES. THE INITIAL INTENSITY IS ASSESSED WITH 
MEDIUM CONFIDENCE. ALTHOUGH THE EYE HAS FILLED WITHIN THE PAST TWO 
HOURS, THE SYSTEM LIKELY ATTAINED PEAK INTENSITY IMMEDIATELY PRIOR TO 
ERC INITIATION, WITH SURFACE WIND ENERGETICS TEMPORARILY LAGGING THE 
STRUCTURAL EVOLUTION. THIS IS REINFORCED BY CONCURRENT SUBJECTIVE AND 
OBJECTIVE SATELLITE ESTIMATES, WHICH CONVERGE AT 120 KNOTS. THE 
ENVIRONMENT REMAINS HIGHLY CONDUCIVE INDEPENDENT OF CORE-SCALE ERC 
DYNAMICS, SUPPORTED BY LOW DEEP-LAYER VWS, EXTREMELY WARM SSTS (29-
30C), AND VIGOROUS RADIAL OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) FAR TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   CIMSS ADT: 112 KTS AT 171130Z
   CIMSS AIDT: 122 KTS AT 171130Z
   CIMSS D-MINT: 120 KTS AT 171033Z
   CIMSS D-PRINT: 122 KTS AT 171130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: EQUATORWARD OUTFLOW CHANNEL; EYEWALL REPLACEMENT
CYCLE (ERC).

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON (TY) 29W IS TRACKING WESTWARD IN THE
AGGREGATE, ALTHOUGH ERRATIC TROCHOIDAL MOTION IS PROJECTED TO PERSIST 
PENDING COMPLETION OF THE ERC. THE EXACT FREQUENCY AND AMPLITUDE OF 
THIS MOTION, WHICH REMAIN HIGHLY UNCERTAIN, WILL GOVERN THE PRECISE 
CPA AND TRACK GEOMETRY WHEN PASSING GUAM. THE CYCLONE WILL TRANSIT THE 
SOUTHERN TIP OF GUAM WITHIN THE NEXT SIX TO EIGHT HOURS. THE CORE WILL 
THEN VEER PROGRESSIVELY NORTHWESTWARD AS THE STR TO THE NORTH SLIDES 
EASTWARD, REPLACED BY A SECONDARY HIGH-PRESSURE CELL TRANSLATING 
RAPIDLY WEST-TO-EAST TO THE NORTH. BY TAU 96, THE STR WILL POSITION 
SOUTHEAST OF HONSHU, DEVELOPING A BROAD WEAKNESS OVER THE EAST CHINA 
SEA. CONSEQUENTLY, TY 29W WILL DECELERATE SHARPLY WHILE MAINTAINING A 
GENERAL NORTHWESTWARD HEADING PAST TAU 96 AS THE STEERING GRADIENT 
RELAXES. REGARDING INTENSITY: THE ACTIVE ERC INTRODUCES COMPETING 
THERMODYNAMIC AND STRUCTURAL INFLUENCES. SPECIFICALLY, THE DURATION OF 
THE EYEWALL REORGANIZATION AND THE TIMING OF NEW EYE EMERGENCE. HAFS-A 
PROJECTS NEW EYE STABILIZATION PRIOR TO THE CYCLONE CROSSING THE 
LONGITUDE OF GUAM, WHEREAS THE HWRF DELAYS ERC COMPLETION, UNTIL POST-
PASSAGE BY GUAM. THE JTWC FORECAST FAVORS THE HWRF SCENARIO, 
PROJECTING THE CORE INTENSITY TO STABILIZE OR DECAY SLIGHTLY IN THE 
NEAR-TERM, FOLLOWED BY RE-INTENSIFICATION ONSET BY TAU 12. BY TAU 24, 
29W IS PROJECTED TO RE-ATTAIN SUPER TYPHOON INTENSITY, PROGRESSING TO 
A PEAK OF 140 KNOTS BY TAU 36. AFTER TAU 36, HAFS-A PROJECTS MULTIPLE 
ERC EXTENDING THROUGH TAU 72; HOWEVER, THE TIMING AND PERIODICITY 
REMAIN HIGHLY UNCERTAIN. THE FORECAST HOLDS INTENSITY STABLE AT 13T 
KNOTS DURING THIS TIMEFRAME, ALTHOUGH SHORT-TERM STRUCTURAL 
FLUCTUATIONS OCCURRING ABOVE AND BELOW THIS MEAN ARE PROBABLE. POST-
TAU 96, 29W WILL ENCOUNTER PROGRESSIVELY LOWER SSTS, EXACERBATED BY 
SELF-INDUCED COLD WATER UPWELLING AMID DECREASING TRANSLATION SPEEDS, 
INITIATING A GRADUAL DECAY THROUGH THE BALANCE OF THE FORECAST.  

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN EXCELLENT AGREEMENT 
THROUGHOUT THE FORECAST PERIOD. CROSS-TRACK SPREAD AT THE GUAM CPA IS 
CONFINED TO LESS THAN 20 NM. THE ENVELOPE GRADUALLY EXPANDS TO 180 NM 
BY TAU 120, BOUNDED EQUATORWARD BY NAVGEM AND POLEWARD BY THE GFS. THE 
JTWC FORECAST HEAVILY FAVORS THE AI CONSENSUS (AICN) MEAN WITH HIGH 
CONFIDENCE. SHORT-TERM TROCHOIDAL CORE OSCILLATION WILL INFLUENCE 
SPECIFIC CPA VALUES AT GUAM. ADDITIONALLY, AS THE ERC COMPLETES ITS 
CYCLE, THE INTENSE WIND FIELD RADII (34-KT, 50-KT, AND 64-KT SECTORS) 
WILL EXPAND. INTENSITY GUIDANCE EXHIBITS SOLID CONGRUENCE. DEEPMIND, 
CTCX, AND HWRF DEPICT AN INTENSITY PLATEAU THROUGH TAU 12, COINCIDENT 
WITH THE ERC, FOLLOWED BY RE-INTENSIFICATION PEAKING NEAR TAU 36. 
PROJECTED PEAKS SPREAD BETWEEN 130 KNOTS (CTCX) AND 150 KNOTS 
(DEEPMIND). THE MAJORITY OF THE SUITE PROJECTS A FLAT INTENSITY REGIME 
BETWEEN TAUS 36 AND 72, WITH WEAKENING POST-TAU 96. THE JTWC INTENSITY 
FORECAST ALIGNS WITH CTCX THROUGH TAU 12, THE FOLLOWING THE BROAD 
SHAPE OF HAFS-A THROUGH THE REMAINDER OF THE FORECAST.

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