Advisories

WDPN32 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (CHOI-WAN) WARNING NR 027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.7N 147.6E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 402 NM EAST-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 23 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
GRADUALLY DEGRADING CONVECTIVE STRUCTURE ASSOCIATED WITH TYPHOON
(TY) 26W. WHILE THE CENTRAL DENSE OVERCAST (CDO) AND CLOUD-FILLED
EYE REMAIN EVIDENT, CLOUD TOP TEMPERATURES SURROUNDING THE CORE
CONTINUE TO WARM, AND THE CONVECTIVE STRUCTURE OVER THE SOUTHWEST
QUADRANT IS BEGINNING TO ERODE. A 061010Z GMI PASS REVEALED AN
INTACT LOWER-LEVEL EYEWALL, WHILE INDICATING WEAKENING IN THE
SOUTHERN PORTION OF THE UPPER-LEVEL EYEWALL. THE ENVIRONMENT IS
LARGELY UNFAVORABLE AS THE SYSTEM CROSSES THE 26-DEGREE CELSIUS
ISOTHERM INTO PROGRESSIVELY COOLER WATERS AND ENCOUNTERS HIGH
VERTICAL WIND SHEAR (VWS). THESE DETRIMENTAL CONDITIONS OUTWEIGH
THE FAVORABLE INFLUENCE OF STRONG POLEWARD OUTFLOW ALOFT. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
OUTLINE OF THE CLOUD-FILLED EYE IN THE SHORTWAVE INFRARED IMAGERY.
THE INITIAL INTENSITY HAS BEEN LOWERED TO 80 KTS WITH MEDIUM
CONFIDENCE, REFLECTING THE DETERIORATING SATELLITE PRESENTATION.
THIS ASSESSMENT IS SUPPORTED BY THE T4.5 DVORAK CLASSIFICATION FROM
PGTW AND THE DECREASING OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) CENTERED EAST OF HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   CIMSS ADT: 63 KTS AT 061140Z
   CIMSS AIDT: 67 KTS AT 061140Z
   CIMSS D-MINT: 73 KTS AT 061008Z
   CIMSS D-PRINT: 81 KTS AT 061210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30-40 KTS
   SST: 25-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST HAS BEEN TRUNCATED FROM
36 HOURS TO 24 HOURS.

FORECAST DISCUSSION: TY 26W IS NOW RACING NORTHEASTWARD AT 23 KTS
ALONG THE NORTHWESTERN PERIPHERY OF THE STR. THE SYSTEM WILL
CONTINUE TO ACCELERATE NORTHEASTWARD THROUGH TAU 24 AS IT BECOMES
INCREASINGLY EMBEDDED IN STRONG DEEP-LAYER WESTERLY FLOW. THE
ENVIRONMENT WILL BECOME INCREASINGLY HOSTILE TO THE TROPICAL
CYCLONE, WITH VWS INCREASING TO 40-50 KTS AND SST DECREASING TO
14-16 DEGREES CELSIUS BY TAU 24. THESE FACTORS WILL CONTINUE TO
ERODE THE INNER CORE, RESULTING IN STEADY WEAKENING. BAROCLINIC
FORCING WILL ALSO INCREASE AS TY 26W INTERACTS WITH A MID-LEVEL
TROUGH EJECTING EASTWARD FROM HONSHU AND BECOMES COUPLED WITH THE
JET STREAM TO THE NORTH. THEREFORE, TY 26W WILL RAPIDLY COMPLETE
EXTRATROPICAL TRANSITION BY TAU 24 WHILE MAINTAINING TYPHOON-FORCE
WINDS. THE EXPANSIVE, POTENT WIND FIELD WILL PRODUCE VERY HIGH
SEAS.

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN EXCELLENT AGREEMENT,
WITH MINIMAL CROSS-TRACK AND ALONG-TRACK SPREAD. THE JTWC FORECAST
TRACK IS SET WITH HIGH CONFIDENCE NEAR THE MULTI-MODEL CONSENSUS
(CONW) DUE TO THE TIGHT CLUSTERING OF THE GUIDANCE. INTENSITY
GUIDANCE IS ALSO IN VERY GOOD AGREEMENT. ALL AVAILABLE AIDS DEPICT
STEADY WEAKENING THROUGH TAU 24, AND THE JTWC INTENSITY FORECAST IS
SET SLIGHTLY ABOVE THE CONSENSUS AT TAU 24, NEAR THE GFS SOLUTION.

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