Advisories

WDPN31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.2N 152.2E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 605 NM EAST OF IWO TO
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
12W WITH A LARGE, SYMMETRICAL, AND CLOUD-FILLED EYE MEASURING 37 NM
IN DIAMETER. ADDITIONALLY, ANIMATED LONGWAVE IR CHANNELS DEPICT
WARMING CLOUDTOPS AND A SLOT OF COLLAPSING DEEP CONVECTION ALONG
THE WESTERN PERIPHERY, PERHAPS SIGNALING THE VERY BEGINNING OF A
FOURTH EYEWALL REPLACEMENT CYCLE (ERC). FURTHERMORE, THE 020600Z
SSMIS SUPPORTS THE THEORY THAT 12W IS ABOUT TO ATTEMPT ANOTHER ERC,
REVEALING A LARGE CRESCENT OF LOW EMISSIVITY STRETCHING ALONG THE
ENTIRE EASTERN SEMICIRCLE. IF THE STORM WERE TO ATTEMPT ANOTHER
ERC, IT WOULD TAKE SIGNIFICANTLY LONGER THAN PAST REPLACEMENT
CYCLES. ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT,
CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM
(30-31 C) SEA SURFACE TEMPERATURES (SST), ROBUST DIVERGENCE ALOFT,
AND SUFFICIENT OCEAN HEAT CONTENT (OHC). THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED EYE IN
ANIMATED MSI. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE SOUTHWESTWARD EXTENSION OF THE DEEP
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 107 KTS AT 020700Z
   CIMSS AIDT: 106 KTS AT 020630Z
   CIMSS D-MINT: 126 KTS AT 020600Z
   CIMSS D-PRINT: 116 KTS AT 020700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG 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 (DOLPHIN) IS FORECAST TO CONTINUE
TRACKING WEST-NORTHWEST AS IT IS STEERED BY THE SOUTHWESTERN
EXTENSION OF THE STR SITUATED TO THE NORTHEAST. AROUND TAU 36,
THE STEERING INFLUENCE WILL SHIFT TO THE SOUTHEASTWARD EXTENSION OF
A SECOND STR CENTERED OVER THE KOREAN PENINSULA, WHICH WILL
CONTINUE THE WEST-NORTHWESTWARD TRACK MOTION THROUGH TAU 120.
BETWEEN TAU 72-120, A STRONG, DEEP-LAYER CYCLONE NORTH OF THE POLAR
FRONT JET WILL WEAKEN THE STEERING RIDGE, INDUCING SLIGHTLY SLOWER
TRACK SPEEDS FOR 12W. REGARDING INTENSITY, 12W IS FORECAST TO
GRADUALLY WEAKEN THROUGH THE FORECAST PERIOD, AS IT CONTENDS WITH
LOWER OHC VALUES AND, IN LATER TAUS, ITS COLD WAKE AS THE SPEED OF
ADVANCE SLOWS. WITH ALL OTHER ENVIRONMENTAL FACTORS REMAINING
SIMILAR TO THE CURRENT CONDITIONS, OHC IS EXPECTED TO BE THE
PRIMARY DRIVER FOR WEAKENING. HOWEVER, SHOULD DOLPHIN ATTEMPT
ANOTHER ERC, IT MAY FAIL TO COMPLETE THE REPLACEMENT, WHICH WOULD
HASTEN WEAKENING AND LEAD TO A STEEPER RATE OF DECAY. 12W'S TIME
OVER HIGH OHC VALUES IS LIMITED, AND A FOURTH ERC WOULD NOT BE ABLE
TO FULLY COMPLETE IN THE TIME REMAINING. THE EYE AND WINDFIELD WILL
REMAIN QUITE LARGE THROUGH TAU 120, BRINGING IMPACTS TO THE
ENTIRETY OF THE JAPANESE RYUKU ISLANDS REGARDLESS OF CENTER
POSITION

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE REMAINS IN
STRONG AGREEMENT THROUGH TAU 120. OF THE MULTI-MODEL CONSENSUS
MEMBERS, ALL MODELS EXCEPT NAVGEM AND GSM DEPICT 12W PASSING NORTH
OF OKINAWA. ADDITIONALLY, ALL EXPERIMENTAL AI-BASED MODELS DEPICT A
TRACK TO THE NORTH OF OKINAWA, LENDING HIGH CONFIDENCE TO THE JTWC
TRACK FORECAST AND POSITIONING RELATIVE TO OKINAWA. THERE ARE MINOR
CONFLICTS IN THE ALONG-TRACK SPREAD, BUT NOT ENOUGH TO
SIGNIFICANTLY DEGRADE THE JTWC TRACK FORECAST CONFIDENCE. RELIABLE
INTENSITY AIDS REMAIN IN GOOD AGREEMENT, WITH THE NOTABLE EXCEPTION
BEING COAMPS-TC (GFS BOUNDARY CONDITIONS), WHICH DEPICTS ADDITIONAL
INTENSIFICATION TO 130 KTS BEFORE WEAKENING. THIS SCENARIO WAS
DEEMED UNLIKELY DUE TO THE ENVIRONMENT AND VERY LARGE EYE SIZE AND
WAS DISCOUNTED WHILE FORECASTING INTENSITY. THE JTWC INTENSITY
FORECAST LIES IN CONCURRENCE WITH THE BULK OF MEMBERS, AND CLOSE TO
GFS, HAFS-A, AND HWRF, WITH MEDIUM CONFIDENCE FROM TAU 0-72. THE
INTENSITY FORECAST IS ASSESSED WITH LOW CONFIDENCE FROM TAU 72-120
DUE TO THE POSSIBILITY OF ADDITIONAL ERC, WHICH WOULD RESULT IN
UNPREDICTABLE INTENSITY FLUCTUATIONS AND FACILITATE QUICKER
WEAKENING.

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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