Advisories

WDPN31 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (SURIGAE) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.6N 130.9E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 166 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 43 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER PEAKING AT 130 KNOTS, TYPHOON (TY) 25W HAS WEAKENED QUICKLY DUE 
TO INCREASING NORTHWESTERLY VERTICAL WIND SHEAR (VWS) EVIDENT IN 
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI), WHICH DEPICTS EXPOSED 
LOW-LEVEL CLOUD LINES OVER THE WESTERN PERIPHERY OF THE SYSTEM. 
ANIMATED RADAR IMAGERY INDICATES EROSION OF THE WESTERN PORTION OF THE 
EYEWALL BUT IT CONTINUES TO SUPPORT THE INITIAL POSITION WITH HIGH 
CONFIDENCE. CIMSS OBJECTIVE INTENSITY ESTIMATES HAVE DECREASED 
SUBSTANTIALLY AND CURRENTLY RANGE FROM 110-124 KNOTS. HOWEVER, ADT HAS 
DECREASED FURTHER TO 115 KNOTS AT 280140Z. DVORAK CURRENT INTENSITY 
ESTIMATES REMAIN HIGH DUE TO CONSTRAINTS WITH DATA-T ESTIMATES RANGING 
FROM T5.5-6.0 (102-115 KNOTS). TO FURTHER COMPLICATE THE INITIAL 
INTENSITY ASSESSMENT, A 272121Z RCM-3 PASS INDICATED A MAXIMUM WIND OF 
135 KNOTS. THE INITIAL INTENSITY IS ASSESSED CONSERVATIVELY AT 120 
KNOTS BASED ON AN OVERALL ASSESSMENT OF THE DETERIORATING CONVECTIVE 
STRUCTURE AND THE WIDE RANGE OF INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.5 - 127 KTS
   RCTP: T6.5 - 127 KTS
   CIMSS ADT: 124 KTS AT 280000Z
   CIMSS AIDT: 110 KTS AT 280000Z
   CIMSS D-MINT: 116 KTS AT 272307Z
   CIMSS D-PRINT: 112 KTS AT 280030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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 25W IS FORECAST TO TRACK NORTHEASTWARD ALONG 
THE NORTHWESTERN PERIPHERY OF THE STR THROUGH THE FORECAST PERIOD, 
WITH STEADY WEAKENING AS IT ENCOUNTERS GRADUALLY INCREASING VERTICAL 
WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT. THE SYSTEM WILL WEAKEN MORE 
RAPIDLY AS IT BEGINS EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 60 AND 
INTERACTS WITH THE FRONTAL ZONE. TY 25W WILL COMPLETE ETT BY TAU 96 AS 
IT TRACKS UNDER THE JET AND BECOMES EMBEDDED WITHIN THE FRONTAL ZONE.   

MODEL DISCUSSION: IN GENERAL, THERE IS INCREASING CONFIDENCE IN
THE TRACK SCENARIO AND JTWC TRACK FORECAST, WITH THE AI-BASED SUITE OF 
MODELS MAINTAINING VERY CONSISTENT FORECASTS OVER THE PAST TWO DAYS 
PLUS. THE CURRENT AI SUITE OF TRACKERS DOES INDICATE A CROSS-TRACK 
SPREAD OF 155NM AT TAU 96 WITH A LARGER ALONG-TRACK SPREAD. INCLUDING 
THE LATEST GFS RUN, WHICH NOW INDICATES A SUSTAINED NORTHEASTWARD 
TRACK, THE DETERMINISTIC MODEL GUIDANCE SUPPORTS THE JTWC FORECAST 
TRACK THROUGH TAU 72 WITH MEDIUM CONFIDENCE. AFTER TAU 72, THERE IS A 
VERY LARGE ALONG-TRACK SPREAD AND LOW CONFIDENCE IN THE JTWC TRACK 
FORECAST. THE JTWC FORECAST REMAINS CONSISTENT AND IS BASED ON CONW 
AND THE AI CONSENSUS. RELIABLE INTENSITY GUIDANCE DEPICTS A SHARP 
WEAKENING TREND THROUGH TAU 36 TO 75 KNOTS THEN A MORE GRADUAL 
WEAKENING TREND THROUGH TAU 96 TO 50 KNOTS. THERE IS STILL 
CONSIDERABLE UNCERTAINTY IN THE WEAKENING TREND AND THE DEGREE TO 
WHICH THE SYSTEM CAN COCOON ITSELF FROM THE EXTENSIVE DRY AIR AND 
INCREASING VERTICAL WIND SHEAR EXPECTED AFTER TAU 48 BUT OVERALL 
CONFIDENCE IN THE INTENSITY FORECAST REMAINS MEDIUM.             

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