Advisories

WDPN32 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (CHAMPI) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.5N 147.3E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 158 NM EAST-SOUTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT
SYSTEM EXHIBITING A NASCENT PINHOLE EYE COUPLED WITH VIGOROUS 
VORTICAL HOT TOWERS (VHTS) DEEPENING WITHIN THE SOUTHERN AND EASTERN 
EYEWALL SECTORS. A 170623Z SSMIS 91GHZ MICROWAVE PASS REVEALED AN 
EXTREMELY COMPACT INNER CORE OF STRONG CONVECTION WITH A PINHOLE 
MICROWAVE EYE, WHILE A STATIONARY BANDING COMPLEX (SBC) IS SITUATED 
ALONG THE SOUTHERN FLANK, WRAPPING TOWARD THE EASTERN FLANK 
APPROXIMATELY 60-75 NM DISTANT FROM THE INNER CORE. THE CLOSED EYE IS 
NOW FULLY RESOLVED ON GUAM WSR-88D WEATHER RADAR, SHOWING THE INNER 
CORE STRUCTURALLY ISOLATED FROM THE SBC. INCIPIENT SIGNATURES OF 
SECONDARY EYEWALL FORMATION (SEF) ARE DETECTABLE IN CURRENT RADAR 
SCANS. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON 
THE PINHOLE EYE RESOLVED IN MSI, CONCURRENT MICROWAVE PASSES, AND 
REAL-TIME RADAR DATA. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM 
CONFIDENCE. SUBJECTIVE AND OBJECTIVE SATELLITE ESTIMATION SCHEMES 
FREQUENTLY UNDER-REPRESENT VORTICES WITH PINHOLE EYES, INTRODUCING A 
PRONOUNCED LOW BIAS; HOWEVER, ADJUSTED AND RAW CIMSS ADT ESTIMATES OF 
T6.0 AND T6.5 ARE ASSESSED TO BE MORE DYNAMICALLY REPRESENTATIVE, AND 
THE JTWC INITIAL INTENSITY (115 KNOTS) IS HEDGED TOWARD THESE HIGHER 
ESTIMATES. ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE FOR 
CONTINUED INTENSIFICATION, CHARACTERIZED BY WEAK DEEP-LAYER VWS (10-15 
KTS), WARM SEA SURFACE TEMPERATURES (29-30C), ROBUST OHC, AND 
EXCELLENT RADIAL OUTFLOW ALOFT AIDED BY AN ACTIVE EQUATORWARD OUTFLOW 
CHANNEL. IMMINENT SEF AND AN ASSOCIATED EYEWALL REPLACEMENT CYCLE 
(ERC) REPRESENT THE SOLE DYNAMICAL LIMITATIONS TO NEAR-TERM 
INTENSIFICATION.

INITIAL WIND RADII BASIS: PERSISTENCE WITH EARLIER SAR DATA. 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T6.0 - 115 KTS
   CIMSS SATCON: 87 KTS AT 170600Z
   CIMSS ADT: 109 KTS AT 170630Z
   CIMSS AIDT: 103 KTS AT 170630Z
   CIMSS D-MINT: 101 KTS AT 170344Z
   CIMSS D-PRINT: 111 KTS AT 170630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE INITIAL INTENSITY HAS BEEN RAISED
SIGNIFICANTLY AND THE RESULTING 12 HOUR FORECAST INTENSITY HAS BEEN
INCREASED TO 130 KNOTS, AS THE SYSTEM IS REACHING ITS CLOSEST POINT
OF APPROACH (CPA) TO GUAM. 

FORECAST DISCUSSION: TY 29W CONTINUES TO TRANSLATE STEADILY
WEST-NORTHWESTWARD ALONG THE EQUATORWARD PERIPHERY OF THE DEEP-LAYER
STR. THE TRANSIT OF A SERIES OF MID-LATITUDE SHORTWAVE TROUGHS TO THE
NORTH WILL REORIENT THE RIDGING AFTER TAU 24, STEERING TY 29W ALONG A 
MORE NORTHWESTWARD TRAJECTORY THROUGH THE REMAINDER OF THE FORECAST. 
BY TAU 120, THE STR WILL HAVE SHIFTED NORTHEAST OF TY 29W, COINCIDENT 
WITH THE DEVELOPMENT OF A BROAD STEERING WEAKNESS OVER THE EAST CHINA 
SEA IVO OKINAWA. CONSEQUENTLY, TY 29W WILL BOTH DECELERATE AS THE 
PRESSURE GRADIENT RELAXES AND INITIATE RECURVATURE POLEWARD TOWARD 
THIS WEAKNESS. THE TRACK HAS FLATTENED SLIGHTLY OVER THE PAST SIX 
HOURS. HOWEVER, AS RAPID INTENSIFICATION (RI) PROGRESSES, AND IN 
PARTICULAR IF SEF INITIATES, TROCHOIDAL CORE WOBBLE WILL INTRODUCE 
SHORT-TERM TRACK VARIATION, WHICH MAY SHIFT THE EXACT CPA POSITION 
RELATIVE TO GUAM DURING THE NEXT 12 HOURS. REGARDING INTENSITY: TY 
29W HAS COMPLETED A PERIOD OF EXTREME RAPID INTENSIFICATION (ERI) 
WITHIN AN OPTIMAL ENVIRONMENT. THERMODYNAMIC PROFILES REMAIN HIGHLY 
CONDUCIVE FOR EXTENDED DEVELOPMENT, AND THE FORECAST CALLS FOR THE 
SYSTEM TO ATTAIN SUPER TYPHOON STATUS (130 KNOTS) BY TAU 12 
COINCIDENT WITH ITS CPA TO GUAM. HOWEVER, THE PROBABILITY OF AN ERC 
(ASSESSED AT 35 PERCENT BY THE CIMSS M-PERC MODEL) INJECTS INCIPIENT 
INTENSITY UNCERTAINTY. SHOULD AN ACTIVE ERC INITIATE PRIOR TO CPA, 
SURFACE WINDS WILL LIKELY PLATEAU OR TEMPORARILY DECAY; ABSENT A 
NEAR-TERM ERC, THE CYCLONE IS HIGHLY PROBABLE TO EXCEED SUPER TYPHOON 
CRITERIA AT CPA. POST-CPA, TY 29W IS FORECAST TO EXTEND 
INTENSIFICATION TO 140 KNOTS PRIOR TO A PROJECTED SECONDARY ERC PHASE 
RESOLVED BY THE HAFS-A SUITE. POST-TAU 96, WEAKENING WILL COMMENCE AS 
THE CORE INTERSECTS LOWER SST THERMODYNAMIC FIELDS AND ELEVATED VWS. 

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN EXCELLENT AGREEMENT,
PARTICULARLY THROUGH TAU 72. CROSS-TRACK DISPERSION AT CPA IS 
CONFINED TO A MERE 15 NM, ALTHOUGH SHORT-TERM TROCHOIDAL MOTION WILL 
GOVERN CPA DEVIATIONS. CROSS-TRACK SPREAD WIDENS TO 80 NM AT TAU 72 
AND 175 NM BY TAU 120. EC-AIFS REPRESENTS THE SOLE EQUATORWARD 
OUTLIER, GOOGLE DEEPMIND AND THE AI CONSENSUS (AICN) OCCUPY THE 
SOUTHERN BOUNDARY OF THE GROUP, AND GFS/GEFS ENSEMBLE MEAN ANCHOR THE 
POLEWARD LIMITS. THE JTWC TRACK CLOSELY MIRRORS AICN THROUGH THE 
FORECAST WITH HIGH CONFIDENCE. INTENSITY GUIDANCE EXHIBITS ELEVATED 
SCATTER. HAFS-A, DTOP, DEEPMIND, AND EXPERIMENTAL WEATHERNEXT-3 
PROJECT RUNAWAY ERI, CAPPING PEAK INTENSITY NEAR 155-165 KNOTS BY TAU 
48 PRIOR TO ERC-INDUCED STABILIZATION AND DOWNSTREAM DECAY POST-TAU 
96. COAMPS-TC PROJECTS A SHORT-TERM PEAK NEAR 125 KNOTS BEFORE CORE 
DISSIPATION INDUCED BY ERC DEPRESSES WINDS TO 110 KNOTS AT TAU 36, 
FOLLOWED BY RE-INTENSIFICATION TO 130 KNOTS BY TAU 72. THE JTWC 
INTENSITY FORECAST ALIGNS WITH DEEPMIND THROUGH TAU 24, FOLLOWS THE 
BROAD SHAPE OF HAFS-A (~25 KNOTS LOWER) THROUGH TAU 72, AND RE-
CONVERGES WITH THE HAFS-A CURVE BY TAU 120. GIVEN THE COMPLEXITIES 
SURROUNDING CORE-SCALE ERC DYNAMICS, THE INTENSITY FORECAST IS 
ASSESSED WITH MEDIUM 
CONFIDENCE THROUGH TAU 72, DROPPING TO LOW CONFIDENCE THEREAFTER. 

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