Advisories

WDPN31 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 041//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.2N 133.5E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 307 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A TYPHOON
(TY) WITH A 10 NM WIDE, CLOUD-FILLED EYE EMBEDDED WITHIN A RAGGED
CENTRAL DENSE OVERCAST (CDO). THE SYSTEM IS ASYMMETRIC, WITH
EXTENSIVE SPIRAL BANDS THAT ARE MOST PROMINENT IN THE NORTHERN
SEMICIRCLE. ROUGHLY 12 HOURS AGO, SAR AND ASCAT PASSES REVEALED TWO
WIND MAXIMA, ONE ASSOCIATED WITH THE INNER CORE AND ANOTHER WITH A
PARTIAL, SECONDARY EYEWALL-LIKE FEATURE. THESE WERE SEPARATED BY A
LARGE MOAT OF GALE-FORCE WINDS, WITH TY-FORCE WINDS PREVIOUSLY
EXTENDING 100 NM OUTWARD IN THE SOUTHERN SEMICIRCLE. HOWEVER, GIVEN
THE PERSISTENT LACK OF DEEP CONVECTION OBSERVED IN THE SOUTHERN
PERIPHERY, IT IS POSSIBLE THAT THE PEAK WINDS ASSOCIATED WITH THE
OUTER BAND HAVE NOW WEAKENED TO BELOW TY STRENGTH. THIS WOULD IMPLY
A SIGNIFICANTLY SMALLER RADIUS OF 64-KT WINDS IN THE SOUTHERN
SEMICIRCLE THAN ANALYZED, THOUGH THE RADII OF GALE- TO STORM-FORCE
WINDS REMAIN LARGE. THE ENVIRONMENT IS FAVORABLE, CHARACTERIZED BY
WARM SEA SURFACE TEMPERATURE (SST) AND LOW VERTICAL WIND SHEAR
(VWS). THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED
ON THE RAGGED EYE IN THE MSI. THE INITIAL INTENSITY HAS BEEN HELD
AT 80 KTS WITH MEDIUM CONFIDENCE, SUPPORTED BY A BLEND OF THE
SUBJECTIVE DVORAK FIXES OF T4.5-5.0 AND THE RECENT OBJECTIVE
ESTIMATES FROM CIMSS RANGING FROM 62 KTS TO 78 KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED OVER THE SEA OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 80 KTS AT 051830Z
   CIMSS ADT: 74 KTS AT 060000Z
   CIMSS AIDT: 78 KTS AT 060000Z
   CIMSS D-MINT: 79 KTS AT 051928Z
   CIMSS D-PRINT: 62 KTS AT 060000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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 WILL BE STEERED WESTWARD ALONG THE
SOUTHERN PERIPHERY OF A STR POSITIONED OVER THE SEA OF JAPAN. A
TROUGH PASSING THROUGH EASTERN SIBERIA WILL FLATTEN THE RIDGE
FURTHER, RESULTING IN A DECREASE IN THE STORM'S TRANSLATION SPEED
FROM 10 KTS AT TAU 24 TO 06 KTS AT TAU 60. AS THE VORTEX APPROACHES
THE CENTRAL COAST OF CHINA, A NEW RIDGE WILL BUILD OVER MAINLAND
JAPAN, DRIVING THE CENTER OF THE CIRCULATION WESTWARD AND ONSHORE.
AFTER TAU 96, IT WILL TURN POLEWARD INTO A WEAKNESS IN THE STR. TY
12W WILL CONTINUE TO TRAVERSE AN ENVIRONMENT OF HIGH SST AND LOW
VWS. FROM TAU 12 TO TAU 48, IT WILL ENCOUNTER A REGION OF HIGHER
OCEAN HEAT CONTENT (OHC) ASSOCIATED WITH THE KUROSHIO CURRENT.
HOWEVER, THE SYSTEM'S LARGE AND COMPLEX STRUCTURE WILL PRECLUDE
SIGNIFICANT INTENSIFICATION DURING THIS PERIOD. THEREFORE, THE
FORECAST CALLS FOR A STEADY INTENSITY THROUGH TAU 60, ALTHOUGH
SLIGHT DEVELOPMENT CANNOT BE RULED OUT. AS TY 12W APPROACHES THE
COAST OF CHINA, THE LOWER OHC COMBINED WITH ITS SLOWER MOTION WILL
RESULT IN GRADUAL WEAKENING. RAPID WEAKENING WILL COMMENCE AFTER
LANDFALL, WITH THE SYSTEM LOSING GALE-FORCE WINDS BY TAU 120.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH IS A DISTINCT
EQUATORWARD OUTLIER, THE TRACK GUIDANCE IS IN EXCEPTIONALLY GOOD
AGREEMENT THROUGH TAU 48 WITH A CROSS-TRACK SPREAD OF 25 NM. THIS
SPREAD INCREASES SIGNIFICANTLY TO 300 NM AT TAU 96 AS MODELS
STRUGGLE TO AGREE ON THE POINT OF LANDFALL OVER CHINA. GFS AND THE
GEFS ENSEMBLE MEAN ARE THE MOST POLEWARD TRACK MEMBERS, BRINGING
THE CIRCULATION CENTER TO NEAR SHANGHAI. GALWEM AND JGSM ARE THE
MOST EQUATORWARD, BRINGING IT ONSHORE NEAR FUZHOU. THE JTWC
FORECAST TRACK IS ALIGNED CLOSELY WITH THE AI CONSENSUS, WHICH
TRENDS BETWEEN THE GFS AND ECMWF SOLUTIONS THROUGH TAU 120. THE
SPREAD AMONG THE INTENSITY AIDS HAS DECREASED. COAMPS-TC, WHICH HAS
BEEN AND CONTINUES TO BE THE HIGH-END OUTLIER, IS DISCOUNTED. THE
SOLUTIONS FROM HWRF AND GFS INDICATE INTENSIFICATION TO 85-90 KTS
AFTER TAU 24, WHILE THOSE FROM HAFS-A, SHIPS, AND THE EXPERIMENTAL
GOOGLE DEEPMIND MODELS LARGELY KEEP THE INTENSITY FLAT. GIVEN THE
CURRENT STRUCTURE AND RECENT HISTORY OF TY 12W, THE JTWC INTENSITY
FORECAST FAVORS THE STEADY-STATE SCENARIO THROUGH TAU 60. THE
WEAKENING SHOWN AFTER TAU 60 FOLLOWS CLOSELY WITH THE INTENSITY
CONSENSUS.

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