Advisories

WDPN31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 037//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.4N 138.3E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 570 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 12W
(DOLPHIN) WITH A CLOUD FILLED EYE BUT MAINTAINING A WELL DEFINED
INNER EYEWALL AND CONVECTIVE ENVELOPE. A 042033Z RCM-3 SAR IMAGE
DEPICTS TWO CONCENTRIC BANDS OF TYPHOON-STRENGTH WINDS, SUPPORTING
THE ONGOING TREND OF CONCENTRIC EYEWALLS AND AN ARRESTED EYEWALL
REPLACEMENT CYCLE (ERC), WITH THE OUTER RING OF MAXIMUM WINDSPEED
BEING OPEN ON THE EASTERN SEMICIRCLE. A 042021Z 91 GHZ SSMIS
MICROWAVE IMAGE FURTHER SUPPORTS THIS, DEPICTING A COMPACT INNER
EYEWALL AND A FRAGMENTED SECONDARY EYEWALL, IN LINE WITH THE WIND
MAXIMA SEEN IN THE SAR IMAGE. ENVIRONMENTAL ANALYSIS REVEALS
FAVORABLE CONDITIONS WITH WARM (29-30 C) SEA SURFACE TEMPERATURES,
LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), AND STRONG RADIAL OUTFLOW
ALOFT, OFFSET ONLY BY LIMITED RELATIVELY DRY AIR ENTRAINMENT AND 
LIKELY UPWELLING COOL WATER. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE DEFINED EYE FEATURE. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SLIGHT SPREAD ACROSS 
AGENCY DVORAK FIXES AND CIMSS OBJECTIVE ESTIMATES.

INITIAL WIND RADII BASIS: WIND RADII ADJUSTED BASED ON A 042033Z
RCM-3 SAR IMAGE.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE
NORTHEAST OVER THE SEA OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 92 KTS AT 042330Z
   CIMSS AIDT: 104 KTS AT 042330Z
   CIMSS D-MINT: 102 KTS AT 041944Z
   CIMSS D-PRINT: 89 KTS AT 050030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: LIMITED DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 IS FORECAST TO CONTINUE ITS WESTWARD
TRACK TOWARDS THE RYUKYU ISLANDS OF JAPAN UNDER THE STEERING
INFLUENCE OF THE SUBTROPICAL RIDGE (STR) CENTERED OVER THE SEA OF
JAPAN. TRACK SPEED IS FORECAST TO SLOW AS TY 12W NEARS OKINAWA AND
BEGINS TO ROUND THE SOUTHWESTERN PERIPHERY OF THE STR. THERE IS
SOME UNCERTAINTY FOR THE FORECAST STEERING ENVIRONMENT PAST TAU 72,
AS SOME MODELS PREDICT THE STR TO WEAKEN MORE SIGNIFICANTLY, THUS
CAUSING A SHARPER POLEWARD TURN AFTER PASSING OVER THE ISLAND CHAIN
VICE A CONTINUED WESTWARD TRACK AND LANDFALL OVER EASTERN CHINA. IN
REGARDS TO INTENSITY, BECAUSE NO IMMEDIATE CONTRACTION OR
CONSOLIDATION OF THE OUTER EYEWALL HAS BEEN OBSERVED, THE SHORT
TERM INTENSITY IS FORECAST TO REMAIN STEADY. AROUND TAU 72, A
WEAKENING TREND IS FORECAST TO BEGIN IN LINE WITH THE SLOW IN TRACK
SPEED AND APPROACH TO LAND. THE OVERALL SIZE OF THE WIND FIELD
REMAINS EXTREMELY LARGE, WITH GALE-FORCE WINDS FORECAST TO IMPACT
THE ENTIRETY OF THE RYUKYU ISLANDS.

MODEL DISCUSSION: MODEL TRACK GUIDANCE HAS COME INTO BETTER
AGREEMENT, NOW WITH ONLY GFS, JGSM, AND NAVGEM DEPICTING THE
POLEWARD TURN, HOWEVER THEY CONTINUE TO DELAY THE TIMING OF THIS
TURN WHICH DOES NOT LEND CONFIDENCE TO THIS SCENARIO. ADDITIONALLY,
THE LARGE MAJORITY OF GOOGLE DEEP-MIND AND ECMWF AI ENSEMBLE
MEMBERS TRACK INTO EASTERN CENTRAL CHINA WITH RAPID WEAKENING OVER
LAND. THE BULK OF ECENS MEMBERS ALSO PREDICT THIS OUTCOME, WITH
ONLY TEN PERCENT OF MEMBERS INDICATING A POLEWARD TURN WHILE OVER
WATER ALONG THE COAST. GEFS HAS THE WIDEST SPREAD OF ENSEMBLE
MEMBERS WITH ROUGHLY A THIRD CURVING POLEWARD OVER WATER SPANNING
FROM CHEJU DO WESTWARD TO SHANGHAI. BASED ON THIS DETAILED ANALYSIS
OF THE ENSEMBLE GUIDANCE, THE OFFICIAL JTWC FORECAST IS PLACED WITH
HIGH CONFIDENCE OUT TO TAU 72 AND MEDIUM FROM TAU 72 TO 120, IN
LINE WITH THE MULTI-MODEL CONSENSUS AND HIGHER PERFORMING AI
CONSENSUS AND AI ENSEMBLES. INTENSITY MODEL GUIDANCE HAS ALSO COME
INTO CLOSER AGREEMENT OF A SLIGHT WEAKENING AND PLATEAU OUT TO TAU
72 BEFORE ANOTHER DROP IN INTENSITY AS IT ROUNDS THE SOUTHWESTERN
PERIPHERY OF THE STR AND APPROACHES LANDFALL. THE OFFICIAL JTWC
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE FOR THE
REMAINDER OR THE FORECAST PERIOD, CLOSELY IN LINE WITH THE
MULTI-MODEL CONSENSUS.

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