Advisories

WDPN32 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (CHOI-WAN) WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.8N 145.8E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 384 NM NORTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 26W HAS WEAKENED SLIGHTLY OVER THE PAST SIX HOURS DUE TO
STRUCTURAL CHANGES AND INCREASING UPPER-LEVEL SOUTHERLY FLOW ALOFT
INTRODUCING AN UPTICK IN VERTICAL WIND SHEAR. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A STILL PERSISTENT
AND COMPACT CORE OF DEEP CONVECTIVE BANDING SURROUNDING A 14 NM
EYE. HOWEVER, THE EYEWALL HAS BECOME INTERMITTENTLY MORE RAGGED, 
CONSISTENT WITH THE NOTED WEAKENING TREND. THE SYSTEM REMAINS VERY 
BROAD, WITH 34-KNOT WIND RADII EXTENDING OVER 300 NM FROM THE STORM 
CENTER IN THE NORTHERN QUADRANTS. THE INITIAL POSITION IS PLACED WITH 
HIGH CONFIDENCE BASED ON SATELLITE EYE FIXES FROM PGTW, RJTD, AND 
RCTP. THE INITIAL INTENSITY OF 95 KTS IS ASSESSED WITH MEDIUM 
CONFIDENCE, CONSERVATIVELY HELD SLIGHTLY ABOVE A CONSENSUS OF THE 
SUBJECTIVE DVORAK AND AUTOMATED INTENSITY ESTIMATES LISTED BELOW TO 
ACCOUNT FOR A 052015Z RCM-1 SAR PASS THAT INDICATED CORE WINDS OF 90 
TO 95 KNOTS.

INITIAL WIND RADII BASIS: 34-KNOT WIND RADII BASED ON PARTIAL
052240Z METOP-B AND 060020Z METOP-C ASCAT PASSES AND PERSISTENCE;
50-KNOT AND 64-KNOT WIND RADII BASED ON 052015Z RCM-1 SAR PASS

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   CIMSS SATCON: 90 KTS AT 052039Z
   CIMSS ADT: 84 KTS AT 052340Z
   CIMSS AIDT: 86 KTS AT 052340Z
   CIMSS D-MINT: 89 KTS AT 052038Z
   CIMSS D-PRINT: 90 KTS AT 052340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: DURING THE 36-HOUR FORECAST PERIOD, TY 26W
WILL ACCELERATE NORTH-NORTHEASTWARD AND COMPLETE EXTRATROPICAL
TRANSITION AS IT MERGES WITH AN A MIDLATITUDE TROUGH APPROACHING
FROM THE NORTHWEST. INCREASING VERTICAL WIND SHEAR AND PASSAGE OVER
COOLER ALONG TRACK SEA SURFACE TEMPERATURES WILL DRIVE A CONTINUED
WEAKENING TREND FOR THE NEXT 12 HOURS. THEREAFTER, FAVORABLE
BAROCLINIC INTERACTION WITH THE APPROACHING TROUGH WILL ENABLE THE
SYSTEM TO MAINTAIN TYPHOON-LEVEL INTENSITY AS AT COMPLETES
TRANSITION INTO AN EXTRATROPICAL LOW. 

MODEL DISCUSSION: PHYSICAL AND AI-BASED FORECAST MODELS ARE IN
EXCELLENT AGREEMENT REGARDING THE PREDICTED TRACK OF TY 26W, WITH
NAVGEM STANDING OUT AS THE SOLE OUTLIER TO THE NORTHWEST OF, AND
SLOWER, THAN THE PRIMARY MODEL GROUPING. SIMILARLY, CONSENSUS
INTENSITY GUIDANCE IS IN EXCELLENT AGREEMENT REGARDING THE
PREDICTED TREND WITH NO NOTEWORTHY OUTLIERS. THE CURRENT FORECAST,
PLACED WITH HIGH CONFIDENCE, IS CONSISTENT WITH CONSENSUS GUIDANCE
FOR BOTH PARAMETERS AND WITH THE PREVIOUS JTWC FORECAST.

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