Advisories

WDPN31 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.0N 147.1E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 316 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 MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
12W WITH A CLOUD-FILLED EYE THAT HAS BEEN DECREASING IN DIAMETER
BUT GAINING A SLIGHT ASYMMETRY. THE PROMINENT DRY SLOT STRETCHES
AROUND THE WESTERN SEMICIRCLE AND INTO THE SOUTHEASTERN QUADRANT.
12W IS MIDWAY THROUGH ITS FOURTH EYEWALL REPLACEMENT CYCLE (ERC),
EVIDENCED BY THE 030309Z AMSR2 MICROWAVE IMAGES, WHICH REVEAL THAT
THE INNER EYEWALL HAS SIGNIFICANTLY SHALLOWED IN THE SOUTHEASTERN
QUADRANT WHILE THE OUTER EYEWALL IS STRENGTHENING AND WRAPS AROUND
APPROXIMATELY THREE QUARTERS OF THE CIRCULATION. THIS ONGOING ERC
IS EXPECTED TO TAKE LONGER TO COMPLETE AND MAY WEAKEN THE STORM
MORE SIGNIFICANTLY THAN PREVIOUS CYCLES. ANIMATED LONGWAVE
RADIATION IMAGERY REVEALS THAT THE CENTER EYE TEMPERATURE IS COOLING
WHILE THE DEEP CONVECTION SURROUNDING THE EYEWALL IS WARMING.
ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT,
CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), GOOD
DIVERGENCE ALOFT, WARM (29-30 C) SEA SURFACE TEMPERATURES (SST).
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
CLOUD-FILLED EYE IN ANIMATED MSI. THE INITIAL INTENSITY OF 95 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND CIMMS AUTOMATED INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 94 KTS AT 030600Z
   CIMSS AIDT: 89 KTS AT 030600Z
   CIMSS D-PRINT: 95 KTS AT 030530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 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 (DOLPHIN) IS FORECAST TO CONTINUE
TRACKING ALONG THE SOUTHWESTERN EXTENSION OF THE STR CENTERED FAR
TO THE NORTHEAST. WITHIN THE NEXT 24 HOURS, THE STEERING INFLUENCE
WILL SHIFT TO A SECOND STR CURRENTLY CENTERED OVER THE KOREAN
PENINSULA. 12W WILL THEN TRACK ALONG THE SOUTHERN PERIPHERY OF THAT
RIDGE THROUGH THE END OF THE FORECAST PERIOD. BETWEEN TAU 72-120,
12W MAY ENCOUNTER A WEAKER STEERING ENVIRONMENT AS A DEEP-LAYER
TROUGH PASSES NORTH OF THE STEERING RIDGE AND WEAKENS IT, THEREBY
REDUCING THE STEERING GRADIENT AND POTENTIALLY SLOWING DOLPHIN'S
SPEED OF ADVANCE. REGARDING INTENSITY, 12W IS FORECAST TO MAINTAIN
A RELATIVELY STEADY INTENSITY THROUGHOUT THE FORECAST PERIOD.
DOLPHIN IS EXPECTED TO WEAKEN SLIGHTLY OVER THE NEXT 24 HOURS AS
THE ERC CONTINUES, THEN SUSTAIN AN INTENSITY OF APPROXIMATELY 85
KTS THROUGH TAU 96 AND WEAKING SLIGHTLY AFTER THAT. THE ENVIRONMENT
IS EXPECTED TO REMAIN CONSISTENT THROUGHOUT THE FORECAST PERIOD,
WITH THE 10-15 KTS OF VWS EXPECTED TO REDUCE TO 5-10 KTS AFTER
ABOUT TAU 36 AND THE OHC VALUES DROPPING SLIGHTLY AROUND TAU
96-120. AS A RESULT, THE PRIMARY DRIVER OF WEAKENING IN THE NEAR
TERM FORECAST IS THE ERC. 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 WIND FIELD WILL
REMAIN QUITE LARGE THROUGH TAU 120, BRINGING IMPACTS TO THE
ENTIRETY OF THE JAPANESE RYUKYU ISLANDS REGARDLESS OF CENTER
POSITION.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 120, HOWEVER THE ALONG-TRACK SPREAD REMAINS
MODERATE. OF THE MULTI-MODEL CONSENSUS MEMBERS, GFS AND GEFS
ENSEMBLE MEAN ARE THE SLOWEST MEMBERS. GFS IS DETECTING A MORE
SIGNIFICANT WEAKENING OF THE STEERING ENVIRONMENT AT THE END OF THE
FORECAST PERIOD, AND IS DEPICTING 12W GETTING CAUGHT IN A COL THAT
IS FORMED BY THE PASSING DEEP-LAYER TROUGH. THIS SCENARIO WOULD
CAUSE SLOWER TRACK SPEEDS THAN WHAT IS DEPICTED IN THE CURRENT
FORECAST. HOWEVER, OTHER RELIABLE MODELS, INCLUDING ECMWF AND THE
EXPERIMENTAL AI MODELS, DEPICT STEADY TRACK SPEEDS AS 12W CROSSES
THE RYUKYU ISLANDS. AS A RESULT, THE JTWC TRACK FORECAST IS NOT
SIGNIFICANTLY IMPACTED AND IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH OVERALL HIGH CONFIDENCE. RELIABLE INTENSITY AIDS ARE
IN GOOD AGREEMENT THROUGH TAU 120, WITH MOST MODELS DEPICTING A
STEADY INTENSITY WITH A SLIGHT WEAKENING TREND. THEREFORE, THE JTWC
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE FROM TAU 0-72
AND LOW CONFIDENCE FROM TAU 72-120 AND LIES CLOSE TO THE
MULTI-MODEL CONSENSUS, GFS, HAFS-A, AND HWRF. UNCERTAINTY REGARDING
THE INTENSITY FORECAST STEMS FROM THE ONGOING ERC AND RESULTING
INTENSITY FLUCTUATIONS.

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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