Advisories

WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.6N 156.2E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 843 NM EAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 12W HAVING JUST COMPLETED ITS EYEWALL REPLACEMENT CYCLE (ERC),
RESULTING IN A LARGE, CLEAR EYE MEASURING APPROXIMATELY 50 NM IN
DIAMETER. THE EYEWALL IS EXPECTED TO CONTRACT OVER THE NEXT SEVERAL
HOURS, POTENTIALLY RESULTING IN A BRIEF REINTENSIFICATION.
ENVIRONMENTAL ANALYSIS REVEALS A HIGHLY FAVORABLE ENVIRONMENT,
CHARACTERIZED BY LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), WARM
(30-31 C) SEA SURFACE TEMPERATURES (SST), ROBUST RADIAL OUTFLOW,
AND OCEAN HEAT CONTENT (OHC) MEASURING 75-100 KJ PER CM SQUARED.
THE 011117Z ASCAT UHR REVEALED MAXIMUM WINDS OF 123 KTS, SUPPORTING
THE INITIAL INTENSITY WITH HIGH CONFIDENCE. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE LARGE EYE FEATURE IN
ANIMATED EIR.

INITIAL WIND RADII BASIS: ADJUSTED RADII USING THE 011121Z METOP-C
ASCAT DATA

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   CIMSS ADT: 117 KTS AT 011310Z
   CIMSS AIDT: 115 KTS AT 011310Z
   CIMSS D-PRINT: 123 KTS AT 011130Z

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

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

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 36-48, THE STEERING INFLUENCE WILL SHIFT TO A
SECOND STR CURRENTLY CENTERED OVER THE KOREAN PENINSULA, REINFORCING 
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 NOW THAT 
IT COMPLETED ERC. 12W MAY MOMENTARILY REINTENSIFY SLIGHTLY WITHIN THE 
NEXT SEVERAL HOURS, BUT IS EXPECTED TO ENCOUNTER A MARGINALLY MORE 
UNFAVORABLE ENVIRONMENT AROUND TAU 24. BY TAU 36, 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. 12W IS FORECAST 
TO WEAKEN GRADUALLY THROUGH TAU 60, THEN WEAKEN AT AN INCREASED PACE 
FROM TAU 72-120. ADDITIONAL EYEWALL REPLACEMENT CYCLES ARE LIKELY AS 
LONG AS THE STORM MAINTAINS TYPHOON INTENSITY, WITH SUBSEQUENT EVENTS 
FURTHER WEAKENING THE CORE AND EXPANDING THE WIND FIELD.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE REMAINS IN
STRONG AGREEMENT THROUGHOUT THE FORECAST PERIOD, SUPPORTING THE
JTWC TRACK FORECAST WITH OVERALL HIGH CONFIDENCE. RELIABLE
INTENSITY AIDS ARE IN GOOD AGREEMENT REGARDING A GRADUAL WEAKENING
OVER TIME. 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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