Advisories

WDPN31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.8N 157.5E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 927 NM EAST-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY) 
12W MIDWAY THROUGH ITS THIRD EYEWALL REPLACEMENT CYCLE (ERC). A
PROMINENT DRY MOAT HAS FORMED ALONG THE WESTERN SIDE OF THE INNER
EYEWALL. THE INNER EYE IS FILLING AND COLLAPSING AS THE OUTER
EYEWALL GAINS STRENGTH. THE COLDEST CONVECTION IS CONFINED TO THE
SOUTHERN SEMICIRCLE, THOUGH THE CLOUD SHIELD REMAINS EXPANSIVE AND
SYMMETRICAL ABOUT THE CENTER. THE ANIMATED LONGWAVE IR REVEALS THE
OUTER EYEWALL HAS FULLY ENVELOPED THE INNER EYEWALL AND SHOULD
BECOME THE DOMINANT EYEWALL IN A FEW HOURS. THE ENVIRONMENT REMAINS
HIGHLY FAVORABLE, CHARACTERIZED BY LOW (5-10 KTS) VERTICAL WIND
SHEAR (VWS), VERY WARM (30-31 C) SEA SURFACE TEMPERATURES (SST),
ROBUST RADIAL OUTFLOW AMPLIFIED BY AN UPPER LEVEL POINT SOURCE
DIRECTLY OVER THE SYSTEM, AND AMPLE OCEAN HEAT CONTENT (OHC). THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
INCREASINGLY RAGGED AND SHALLOWING, BUT STILL PROMINENT, CENTRAL
EYE FEATURE IN ANIMATED MSI. THE INITIAL INTENSITY OF 120 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE CONCURRENCE OF AGENCY
DVORAK FIXES AND THE CIMSS AUTOMATED INTENSITY ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 126 KTS AT 010730Z
   CIMSS ADT: 117 KTS AT 010630Z
   CIMSS AIDT: 109 KTS AT 010630Z
   CIMSS D-PRINT: 123 KTS AT 010630Z
   CIMSS D-MINT: 123 KTS AT 010651Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: CURRENTLY UNDERGOING AN EYEWALL REPLACEMENT CYCLE

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: TY 12W (DOLPHIN) WILL CONTINUE TRACKING
NORTHWESTWARD WHILE IT REMAINS UNDER THE INFLUENCE OF THE STEERING
STR CENTERED TO ITS NORTHEAST. THE SOUTHWESTWARD RIDGE EXTENSION
WILL CONTINUE TO BUILD, DRIVING THE SYSTEM FURTHER NORTHWESTWARD.
BEGINNING AROUND TAU 60, THE STEERING INFLUENCE WILL SHIFT TO A
SECOND STR CURRENTLY CENTERED OVER THE KOREAN PENINSULA, WHICH WILL
CONTINUE THE NORTHWESTWARD TRACK MOTION THROUGH TAU 120. REGARDING
INTENSITY, DOLPHIN IS FORECAST TO GRADUALLY WEAKEN THROUGH THE END
OF THE FORECAST PERIOD, AND IS NOT EXPECTED TO SIGNIFICANTLY
RECOVER FROM THE ONGOING ERC. 12W MAY MOMENTARILY INTENSIFY
SLIGHTLY ONCE COMPLETING ERC, BUT IS EXPECTED TO ENCOUNTER A
SOMEWHAT LESS FAVORABLE ENVIRONMENT AROUND TAU 24-48. BY TAU 48,
VWS WILL INCREASE TO 15-20 KTS AND OHC VALUES WILL
DECREASE TO 50-75 KJ PER CM SQUARED, CAUSING INCREASED IMPACTS FROM
THE STORM'S COLD WAKE. ALL ELSE REMAINING EQUAL, 12W IS FORECAST TO
WEAKEN GRADUALLY THROUGH TAU 72, THEN WEAKEN AT AN INCREASED PACE
FROM TAU 72-120. ADDITIONAL EYEWALL REPLACEMENT CYCLES ARE LIKELY,
AS THE STORM MAINTAINS TYPHOON INTENSITY, WITH SUBSEQUENT EVENTS
FURTHER WEAKENING THE CORE BUT EXPANDING THE WIND FIELD.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE REMAINS IN
STRONG AGREEMENT THROUGHOUT THE FORECAST, WITH ONLY MINOR
DEVIATIONS IN CROSS-TRACK AND ALONG-TRACK SPREAD. AS A RESULT, THE
JTWC TRACK IS PLACED WITH OVERALL HIGH CONFIDENCE. RELIABLE
INTENSITY AIDS ARE IN GOOD AGREEMENT REGARDING A GRADUAL WEAKENING
OVERTIME. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE FROM TAU 0-72 AND LOW
CONFIDENCE FROM TAU 72-120. UNCERTAINTY IN THE INTENSITY FORECAST
STEMS FROM THE POTENTIAL OF FUTURE EYEWALL REPLACEMENTS AND THEIR
UNKNOWN IMPACTS TO BOTH THE INTENSITY AND WIND FIELD.

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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