Advisories

WDPN33 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (KOGUMA) WARNING NR 026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.3N 147.8E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 355 NM EAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 47 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 27W MAINTAINS AN IMPRESSIVE PRESENTATION IN ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI). A CIRCULAR, CLEAR EYE
MEASURING 20 NM IN DIAMETER AND AS WARM AS 17 DEGREES CELSIUS IS
EMBEDDED IN A SYMMETRIC CENTRAL DENSE OVERCAST (CDO). THE CIRRUS
CANOPY HAS BECOME LESS SMOOTH, AND A SURROUNDING OUTER CONVECTIVE
RING HAS DEVELOPED. A 101953Z RCM-3 SAR PASS INDICATED EYEWALL
WINDS OF 110-120 KTS AND A SECONDARY, WEAKLY DEFINED WIND MAXIMUM
20 NM FROM THE CENTER. A SUBSEQUENT 110611Z SSMIS PASS REVEALED
CONCENTRIC CONVECTIVE RINGS SEPARATED BY A MOAT, WITH THE INNER
EYEWALL BEGINNING TO ERODE, SUPPORTING THE ASSESSMENT THAT AN
EYEWALL REPLACEMENT CYCLE (ERC) IS UNDERWAY. TY 27W IS TRACKING
NORTH-NORTHWESTWARD AT 9 KTS IN A FAVORABLE ENVIRONMENT OF WARM SEA
SURFACE TEMPERATURES (SST) OF 27-28 DEGREES CELSIUS, LOW VERTICAL
WIND SHEAR (VWS) OF 5-10 KTS, AND MODERATE RADIAL OUTFLOW ALOFT.
BASED ON THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES RANGING
FROM 103 KTS TO 117 KTS, THE SAR DATA, AND THE DEGRADATION OF THE
INNER EYEWALL, THE INITIAL INTENSITY IS SET AT 115 KTS, DOWN FROM
THE RE-ANALYZED 120-KT INTENSITY AT 110000Z, WITH MEDIUM
CONFIDENCE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE WELL-DEFINED EYE IN MSI.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED NEAR 28N 167E

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   CIMSS SATCON: 103 KTS AT 110600Z
   CIMSS ADT: 112 KTS AT 110600Z
   CIMSS AIDT: 117 KTS AT 110600Z
   CIMSS D-MINT: 116 KTS AT 110400Z
   CIMSS D-PRINT: 116 KTS AT 110600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

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 IS GRADUALLY TURNING POLEWARD ALONG THE
WESTERN PERIPHERY OF A LARGE ANTICYCLONE POSITIONED OVER THE
CENTRAL NORTH PACIFIC. THE SYSTEM WILL CROSS THE STR AXIS BETWEEN
TAU 12 AND TAU 24, AFTER WHICH IT WILL GRADUALLY TURN
NORTHEASTWARD. BY TAU 36, THE VORTEX WILL BE ALONG THE NORTHWESTERN
FLANK OF THE RIDGE AND ACCELERATE INTO THE DEEP-LAYER MID-LATITUDE
WESTERLY FLOW. THE ONGOING ERC WILL RESULT IN CONTINUED WEAKENING
AS THE INNER EYEWALL ERODES AND THE OUTER CONVECTIVE RING BECOMES
DOMINANT. FURTHERMORE, THE SYSTEM WILL SOON MOVE OVER A TONGUE OF
MARGINALLY WARM SST OF AROUND 26 DEGREES CELSIUS AND LOW OCEAN HEAT
CONTENT ASSOCIATED WITH COLD WAKES LEFT BEHIND BY FORMER TY 26W AND
15E. CONSEQUENTLY, STEADY WEAKENING WILL OCCUR THROUGH TAU 24. VWS
WILL INCREASE TO OVER 30 KTS BY TAU 36 AS THE VORTEX COMES UNDER
THE SOUTHERN PERIPHERY OF A JET STREAM, AND THE CIRCULATION WILL
CROSS THE 26-DEGREE CELSIUS ISOTHERM INTO MUCH COOLER WATERS,
RESULTING IN A FASTER RATE OF WEAKENING. WEAK BAROCLINIC PROCESSES
AND ENHANCED POLEWARD OUTFLOW WILL MODERATE THE RATE OF WEAKENING
AFTER TAU 48. TY 27W WILL BEGIN EXTRATROPICAL TRANSITION (ETT) BY
TAU 72 AND COMPLETE ETT BY TAU 96.

MODEL DISCUSSION: TRACK GUIDANCE IS IN EXCELLENT AGREEMENT THROUGH
THE ENTIRE FORECAST PERIOD, WITH A CROSS-TRACK SPREAD OF 45 NM AT
TAU 24, 80 NM AT TAU 48, AND 125 NM AT TAU 72. ALONG-TRACK SPREAD
IS EXCELLENT, MEASURING 90 NM AT TAU 96. BY TAU 72 AND TAU 96,
ECMWF, GFS, AND NAVGEM DEPICT A MORE POLEWARD TRACK COMPARED TO THE
AI MODELS. GOOGLE DEEPMIND IS CLOSELY ALIGNED WITH THE MULTI-MODEL
CONSENSUS (CONW) AND THE AI-MODEL MEAN. THE JTWC FORECAST TRACK HAS
CHANGED LITTLE FROM THE PREVIOUS FORECAST AND IS PLACED WITH HIGH
CONFIDENCE NEAR CONW THROUGH TAU 96. THE INTENSITY AIDS ARE TIGHTLY
CLUSTERED, DEPICTING A STEADY TO RAPID WEAKENING TREND THROUGH TAU
60, FOLLOWED BY A SLOWER RATE AT TAU 72 AND TAU 96. THE JTWC
INTENSITY FORECAST IS SET WITH HIGH CONFIDENCE, ALIGNING WITH THE
TIGHT GROUPING OF SOLUTIONS FROM DEEPMIND, HAFS-A, AND COAMPS-TC.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: HIGH//
NNNN