Advisories

WDPN31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.6N 150.9E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 530 NM EAST OF IWO TO
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 12W MIDWAY THROUGH ITS FOURTH EYEWALL REPLACEMENT CYCLE (ERC),
WITH A DISTINCT MOAT ALREADY WRAPPED MOST OF THE WAY AROUND THE
INNER EYEWALL.  THE CLOUD SHIELD IS BECOMING MORE SPARCE AS THE
DEEPEST CONVECTION HAS COLLAPSED AND CLOUDTOPS HAVE WARMED TO -75C
OR LESS. THIS ONGOING ERC IS EXPECTED TO TAKE LONGER AND MAY WEAKEN
THE STORM MORE SIGNIFICANTLY THAN PREVIOUS CYCLES. ENVIRONMENTAL
ANALYSIS REVEALS A FAVORABLE ENVIRONMENT, CHARACTERIZED BY LOW
(10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM (30-31 C) SEA SURFACE
TEMPERATURES, AND ROBUST DIVERGENCE ALOFT. 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: ADJUSTED 50 KT AND 64 KT WIND RADII USING
THE 020753Z RCM-1 SAR DATA

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: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 99 KTS AT 021130Z
   CIMSS AIDT: 100 KTS AT 091130Z
   CIMSS D-PRINT: 108 KTS AT 021130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: ONGOING EYEWALL REPLACEMENT CYCLE

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. VALUES ARE EXPECTED TO BE BETWEEN 50-75 KJ PER CM SQUARED 
BEGINNING BEFORE TAU 12. IN THE LIKELY SCENARIO THAT DOLPHIN FAILS TO 
COMPLETE THE ONGOING ERC, IT COULD HASTEN WEAKENING AND COMPOUND THE 
NEGATIVE EFFECTS OF LOWER OHC. 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 GSM DEPICT 12W PASSING NORTH OF OKINAWA.
ADDITIONALLY, ALL BUT ONE EXPERIMENTAL AI-BASED MODEL DEPICT A
TRACK TO THE NORTH OF OKINAWA, LENDING HIGH CONFIDENCE TO THE JTWC
TRACK FORECAST AND POSITIONING RELATIVE TO OKINAWA. ALONG-TRACK
SPREAD MEASURES AT APPROXIMATELY 270 NM, WITH THE ECMWF ENSEMBLE
MEAN AS THE FASTEST TRACK AND THE GFS DETERMINISTIC AS THE SLOWEST
TRACK. THE DISCREPANCY IS NOT SIGNIFICANT ENOUGH TO DEGRADE TRACK
FORECAST CONFIDENCE, SINCE MOST MODELS ARE IN TIGHT AGREEMENT. AS A
RESULT, THE JTWC TRACK FORECAST IS PLACED WITH OVERALL HIGH
CONFIDENCE. RELIABLE INTENSITY AIDS REMAIN IN GOOD AGREEMENT, WITH
THE NOTABLE EXCEPTIONS BEING BOTH COAMPS-TC BOUNDARY CONDITION
SOLUTIONS, WHICH DEPICT ADDITIONAL INTENSIFICATION TO 135 KTS
BEFORE WEAKENING. THIS SCENARIO WAS DEEMED UNLIKELY DUE TO THE
ENVIRONMENT AND VERY LARGE EYE SIZE, AND BOTH MODELS WERE
DISCOUNTED WHILE FORECASTING INTENSITY. THE JTWC INTENSITY FORECAST
LIES IN CONCURRENCE WITH THE MULTI-MODEL CONSENSUS, GFS, HAFS-A,
AND HWRF, WITH OVERALL LOW CONFIDENCE, WITH UNCERTAINTY STEMMING
FROM THE ONGOING ERC AND RESULTING INTENSITY FLUCTUATIONS.

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