Advisories

WDPN31 PGTW 312100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.8N 159.1E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 425 NM WEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 49 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
WELL-DEFINED EYE EMBEDDED WITHIN A DETERIORATED CENTRAL DENSE
OVERCAST (CDO). THE 17 TO 19 NM WIDE EYE REMAINS QUITE WARM AT +10
TO +15 DEGREES CELSIUS, SURROUNDED BY CLOUD TOP TEMPERATURES OF -70
TO -75 DEGREES CELSIUS. THE TYPHOON (TY) IS TRAVERSING VERY WARM
SEA SURFACE TEMPERATURES (SST) OF 30-31 DEGREES CELSIUS AND VERY
HIGH OCEAN HEAT CONTENT OF 140 KJ PER CM2 WITHIN A REGION OF LOW
VERTICAL WIND SHEAR (VWS), WHICH HAS ENABLED EFFICIENT VENTILATION
ALOFT IN ALL DIRECTIONS. THE PRIMARY FACTOR PREVENTING
INTENSIFICATION IS THE ONGOING EYEWALL REPLACEMENT CYCLE (ERC). A
311446Z AMSR2 89 GHZ IMAGE CLEARLY REVEALS CONCENTRIC RINGS
SURROUNDING THE CENTER. HOWEVER, SATELLITE TRENDS IN THE PAST 12
HOURS INDICATE THAT THE INNER CORE HAS REMAINED PERSISTENT, AND THE
OUTER RING HAS STRUGGLED TO BECOME THE PRIMARY EYEWALL. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
WELL-DEFINED, CIRCULAR EYE. THE INITIAL INTENSITY HAS BEEN LOWERED
TO 125 KTS WITH MEDIUM CONFIDENCE, WHICH REFLECTS THE SUBJECTIVE
DVORAK FINAL T-NUMBERS THAT HAVE FALLEN TO 6.0-6.5 AND IS SUPPORTED
BY OBJECTIVE ESTIMATES FROM CIMSS RANGING FROM 120 KTS TO 136 KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T7.0 - 140 KTS 
   RCTP: T7.5 - 155 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 130 KTS AT 310330Z
   CIMSS ADT: 124 KTS AT 1730Z
   CIMSS AIDT: 120 KTS AT 1730Z
   CIMSS D-MINT: 134 KTS AT 311536Z
   CIMSS D-PRINT: 136 KTS AT 311730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL

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 12W CONTINUES TO MOVE NORTHWESTWARD,
STEERED ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYER STR
CENTERED NEAR 40N 175E. FOR THE NEXT 24 HOURS, THE SYSTEM WILL
TRACK TOWARD A WEAKNESS IN THE RIDGE, WHICH HAS BEEN INDUCED BY A
LONGWAVE TROUGH EXTENDING SOUTH OF THE KURIL ISLANDS. BY TAU 36,
THE WESTERN EXTENSION OF THE STR WILL BUILD IN AND BLOCK THE VORTEX
FROM GAINING SIGNIFICANT ADDITIONAL LATITUDE, FORCING A GRADUAL
TURN TOWARD THE WEST. BY TAU 72, A SEPARATE RIDGE CENTERED OVER THE
KOREAN PENINSULA WILL BECOME THE PRIMARY STEERING INFLUENCE,
MAINTAINING THE LARGELY WESTWARD TRAJECTORY TOWARD THE RYUKYU
ISLANDS THROUGH TAU 120. THE SYSTEM HAS A 12-24 HOUR WINDOW OF
OPPORTUNITY TO INTENSIFY WITHIN AN ENVIRONMENT OF VERY HIGH OHC AND
LOW VWS. THE FORECAST CALLS FOR THE ERC TO END WITHIN THE NEXT 12
HOURS, WHICH WILL ALLOW FOR INTENSIFICATION IN THE NEAR TERM. IF
THE ERC CAN FINISH IN THE NEXT 6 HOURS, THIS SYSTEM MAY CONCEIVABLY
REACH 140 KTS. AFTER TAU 24, ENVIRONMENTAL CONDITIONS WILL BECOME
LESS IDEAL, CHARACTERIZED BY LOWER OHC AND HIGHER VWS. ALTHOUGH THE
SST WILL REMAIN HIGH AT 29-31 DEGREES CELSIUS THROUGH TAU 120, THE
DIMINISHING UNDERLYING HEAT CONTENT WILL BE INSUFFICIENT TO SUSTAIN
A VERY HIGH-INTENSITY STORM. THEREFORE, THESE LESS FAVORABLE
CONDITIONS WILL LEAD TO GRADUAL WEAKENING THROUGH THE END OF THE
FORECAST PERIOD. SUBSEQUENT ERC EVENTS WILL LIKELY LEAD TO LESS
PREDICTABLE FLUCTUATIONS IN INTENSITY NOT CAPTURED BY THE FORECAST
AND AN EXPANSION OF THE WIND FIELD.

MODEL DISCUSSION: WITH THE EXCEPTION OF HWRF, WHICH IS A NOTABLE
POLEWARD OUTLIER, THE MODELS ARE IN VERY TIGHT AGREEMENT. THE
SPREAD IS MUCH TIGHTER THAN THE CLIMATOLOGICAL AVERAGE, INCREASING
FROM 60 NM AT TAU 48 TO 160 NM AT TAU 120. THE GUIDANCE ENVELOPE
SHOWS INTERMINGLING OF THE AI AND PHYSICS-BASED MODELS, INDICATING
NO SIGNIFICANT BIAS RELATED TO MODEL TYPE. IN THE EXTENDED PERIOD,
THE GFS, ECMWF, AND EXPERIMENTAL GOOGLE DEEPMIND MODELS LEAN MORE
EQUATORWARD, WHILE NAVGEM, GALWEM, HAFS-A, THE GEFS AND ECENS
ENSEMBLE MEANS, AND THE AI MODEL CONSENSUS BIAS POLEWARD. THE JTWC
FORECAST TRACK IS POSITIONED WITH HIGH CONFIDENCE ALONG THE
MULTI-MODEL CONSENSUS THROUGH TAU 96 AND THEN HEDGES JUST SOUTH OF
CONSENSUS AT TAU 120. THE INTENSITY GUIDANCE FAVORS A PERIOD OF
STEADY INTENSITY OR SLIGHT RE-INTENSIFICATION IN THE NEXT 24 HOURS.
AMONG THE INTERPOLATED AIDS, COAMPS-TC IS THE STRONGEST MEMBER WITH
A PEAK OF 135 KTS, WHILE THE HAFS-A PARENT MODEL PREDICTS A 140-KT
PEAK. AFTER THIS NEAR-TERM WINDOW, THE HAFS-A, HWRF, AND DEEPMIND
SOLUTIONS DEPICT GRADUAL WEAKENING. THE JTWC INTENSITY FORECAST
ACCOUNTS FOR BOTH THE ONGOING ERC AND THE POTENTIAL FOR A BRIEF
PERIOD OF DEVELOPMENT BY SHOWING SLIGHT INTENSIFICATION TO 130 KTS
AT TAU 12. THEREAFTER, THE FORECAST ALIGNS WITH THE MODEL TRENDS
AND SLOWLY WEAKENS TY 12W FROM TAU 24 TO TAU 120.

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