Advisories

WDPN32 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (CHOI-WAN) WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.4N 145.5E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 312 NM NORTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 43 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 26W HAS WEAKENED SLIGHTLY WHILE MOVING POLEWARD OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
DEPICTS A PERSISTENT, COMPACT CORE OF DEEP CONVECTIVE BANDING 
SURROUNDING A 12 NM EYE. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON A MICROWAVE EYE FEATURE EVIDENT IN 051550Z AMSR2 
MICROWAVE IMAGERY AND RECENT MULTI-AGENCY POSITION FIXES. THE INITIAL
INTENSITY OF 105 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A
CONSENSUS OF THE SUBJECTIVE DVORAK AND AUTOMATED INTENSITY ESTIMATES 
LISTED BELOW.

INITIAL WIND RADII BASIS: 051402Z OCEANSAT-3 PASS FOR THE 34-KNOT
WIND RADII AND OBJECTIVE BEST TRACK AND PERSISTENCE FOR THE 50- AND
64-KNOT WIND RADII

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.5 - 102 KTS
   CIMSS SATCON: 106 KTS AT 051637Z
   CIMSS ADT: 94 KTS AT 051730Z
   CIMSS AIDT: 98 KTS AT 051730Z
   CIMSS D-MINT: 101 KTS AT 051639Z
   CIMSS D-PRINT: 92 KTS AT 051830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 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: TY 26W WILL TURN NORTH-NORTHEASTWARD,
ACCELERATE INTO THE MIDLATITUDE WESTERLY FLOW PATTERN, AND MERGE
WITH AN APPROACHING TROUGH DURING THE 36-HOUR FORECAST PERIOD. SLOW
WEAKENING IS ANTICIPATED OVER THE NEXT 12 HOURS AS FAVORABLE
POLEWARD OUTFLOW ALOFT AND PASSAGE OVER WARM WATER ARE OFFSET BY
SLOWLY INCREASING SOUTHWESTERLY VERTICAL WIND SHEAR. THEREAFTER,
FAVORABLE BAROCLINIC INTERACTION WITH THE APPROACHING TROUGH WILL
BALANCE THE NEGATIVE IMPACTS OF INCREASING VERTICAL WIND SHEAR, 
ENTRAINMENT OF DRIER AIR AND PASSAGE OVER COOLER WATER TO ENABLE 
TRANSITION OF 26W INTO A VERY STRONG EXTRATROPICAL LOW.

MODEL DISCUSSION: NUMERICAL MODEL TRACK FORECAST GUIDANCE IS IN
VERY GOOD AGREEMENT IN TERMS OF BOTH DIRECTION AND SPEED, AND THE
CURRENT TRACK FORECAST IS CONSISTENT WITH THE PREVIOUS JTWC
FORECAST WITH HIGH CONFIDENCE. INTENSITY FORECAST GUIDANCE IS ALSO
IN GOOD AGREEMENT, WITH ALL MODELS DEPICTING FAVORABLE BAROCLINIC
INTERACTION WITH THE APPROACHING MIDLATITUDE TROUGH AS THE SYSTEM
TRANSITIONS. THE CURRENT INTENSITY FORECAST IS ALSO CONSISTENT WITH
THE PREVIOUS JTWC FORECAST WITH HIGH CONFIDENCE.

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