Advisories

WDPN33 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (KOGUMA) WARNING NR 028//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.1N 147.3E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 627 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 27W CONTINUES TO UNDERGO AN EYEWALL REPLACEMENT CYCLE
(ERC) WITH GRADUAL WEAKENING EVIDENT OVER THE PAST 12 HOURS. ANIMATED 
ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN ERODING INNER 
EYEWALL AND WARMING CLOUD TOP TEMPERATURES. AN 111801Z GMI 89GHZ COLOR 
COMPOSITE MICROWAVE IMAGE INDICATES THE ERC IS ALMOST COMPLETE, 
REVEALING A DOMINANT OUTER EYEWALL, REMNANT INNER EYEWALL, WITH A 
MICROWAVE EYE SIZE OF ABOUT 45NM DIAMETER. UPPER-LEVEL OUTFLOW REMAINS 
VIGOROUS WITH RADIAL OUTFLOW AND AN ENHANCED POLEWARD OUTFLOW CHANNEL 
REVEALED IN ANIMATED WATER VAPOR IMAGERY. THERE IS HIGH CONFIDENCE IN 
THE INITIAL POSITION BASED ON THE CLOUD-FREE EYE IN EIR SATELLITE 
IMAGERY AND THE WELL-DEFINED MICROWAVE EYE. THE INITIAL INTENSITY IS 
ASSESSED AT 105 KNOTS BASED ON A BLEND OF CIMSS OBJECTIVE ESTIMATES 
AND DVORAK CURRENT INTENSITY AND DATA-T ESTIMATES. THE WIND RADII WERE 
ADJUSTED RECENTLY BASED ON THE 111150Z ASCAT-C UHR IMAGE WITH MEDIUM 
CONFIDENCE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
ENTRENCHED TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   CIMSS SATCON: 103 KTS AT 111800Z
   CIMSS ADT: 107 KTS AT 111800Z
   CIMSS AIDT: 106 KTS AT 111800Z
   CIMSS D-MINT: 98 KTS AT 111757Z
   CIMSS D-PRINT: 99 KTS AT 111800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: ENHANCED POLEWARD OUTFLOW CHANNEL

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 27W WILL RECURVE NORTH-NORTHEASTWARD TO
NORTHEASTWARD OVER THE NEXT 12 TO 24 HOURS AS IT ROUNDS THE STR
AXIS. AS THE 45NM OUTER EYEWALL CONSOLIDATES AND CONTRACTS POST-ERC, 
BRIEF, SLIGHT REINTENSIFICATION IS POSSIBLE WITHIN THE NEXT 6-12 HOURS 
UNDER LOW VWS AND WARM WATERS. IN GENERAL, THE SYSTEM IS EXPECTED TO 
WEAKEN FROM TAU 12 TO TAU 24 AS VWS INCREASES TO 15-20 KNOTS. AFTER 
TAU 24, THE SYSTEM WILL ACCELERATE NORTHEASTWARD WITH MORE SIGNIFICANT 
WEAKENING AS IT ENCOUNTERS STRONG (30-40 KNOTS) VWS ASSOCIATED WITH 
THE MIDLATITUDE WESTERLIES AND COOLER SEA SURFACE TEMPERATURES (SST) 
LESS THAN 24C. EXTRA-TROPICAL TRANSITION (ETT) WILL COMMENCE NEAR TAU 
48, WHEN TY 27W BEGINS TO INTERACT WITH THE UPPER-LEVEL JET STREAM AND 
MODERATE BAROCLINIC ZONE. THE SYSTEM WILL COMPLETE ETT BY TAU 72 AS IT 
TRACKS UNDER THE JET STREAM, GAINS WEAK TO MODERATE FRONTAL 
CHARACTERISTICS AND TRACKS OVER COLD SST VALUES (18-20C) WITH 
EXTENSIVE DRY AIR ENTRAINMENT.

MODEL DISCUSSION: OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC
TRACK AND INTENSITY FORECAST. PHYSICS-BASED AND AI-BASED GUIDANCE
REMAINS IN TIGHT AGREEMENT, WITH CONW, AICN AND GDMI IN CLOSE
AGREEMENT AT EVERY FORECAST TAU. RELIABLE INTENSITY GUIDANCE IS IN
GOOD AGREEMENT SUPPORTING THE STEADY WEAKENING FORECAST PHILOSOPHY.

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