WDPN31 PGTW 130300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (NAKRI) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.1N 140.3E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 135 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS
OF DEEP CONVECTION WRAPPING INTO THE CENTER OF TYPHOON (TY) 29W.
THE LOW-LEVEL CIRCULATION CENTER (LLCC) IS OBSCURED BY THE DEEP
CONVECTION. DESPITE THE OBSCURATION ON ANIMATED MSI, THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 130000Z METOP-B
MHS 89GHZ IMAGE REVEALING A LOW-LEVEL CIRCULATION CENTER AND
UPPER-LEVEL CONVECTIVE BANDING. THE INITIAL INTENSITY OF 75 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE
FIXES LISTED BELOW SUPPORTED BY AN EARLIER RCM-1 SYNTHETIC APERTURE
RADAR WIND SPEED IMAGE INDICATING WIND SPEEDS OF 75-80KTS.

INITIAL WIND RADII BASIS: 122031Z SAR DATA 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE SOUTHEAST
ENHANCED BY THE JET TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 74 KTS AT 122030Z
   CIMSS AIDT: 74 KTS AT 122030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 29W WILL CONTINUE ON AN EAST-NORTHEASTWARD
TRACK ENHANCED BY THE ZONAL FLOW OF THE SUBTROPICAL JET TO THE
NORTH FOR THE REMAINDER OF THE FORECAST PERIOD. AS THE SYSTEM
BECOMES FURTHER EMBEDDED WITHIN THE JET, VERTICAL WIND SHEAR IS
ANTICIPATED TO BECOME UNFAVORABLE, RESULTING IN A WEAKENING TREND
THAT WILL COMMENCE WITHIN THE NEXT 24 HOURS. SEA SURFACE
TEMPERATURES WILL DROP UNFAVORABLY BELOW 26 DEGREES AS TY 29W
TRACKS NORTH OF THE KUROSHIO CURRENT. EXTRATROPICAL TRANSITION WILL
COMMENCE BY TAU 38, MARKED BY FRONTOGENESIS, A VERTICAL TILT WITH
HEIGHT, AND DEVELOPMENT OF A COLD CORE. BY THE END OF THE FORECAST
PERIOD, TY 29W WILL HAVE FULLY TRANSITIONED TO A 50KT EXTRATROPICAL
CYCLONE.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN STRONG
AGREEMENT THAT TY 29W WILL TRACK ALONG THE NORTHERN PERIPHERY OF
THE SUBTROPICAL RIDGE TO THE SOUTHEAST. THE CROSS-TRACK SPREAD BY
TAU 48 IS 54NM, LENDING HIGH CONFIDENCE TO THE TRACK FORECAST. THE
INTENSITY GUIDANCE FOLLOWS SUIT AND IS IN GOOD AGREEMENT THAT TY
29W WILL EITHER STAGNATE FOR THE FIRST TWELVE HOURS OR GRADUALLY
WEAKEN CONTINUOUSLY FOR THE ENTIRETY OF THE FORECAST PERIOD.

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