WDPN31 PGTW 132100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (NARI) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.1N 143.1E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 256 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SPIRAL
BANDS OF DEEP CONVECTION OBSCURING A LOW-LEVEL CIRCULATION CENTER
HIGHLIGHTING THE IMPROVED STRUCTURE OF TROPICAL STORM (TS) 06W.
HOWEVER, EIR HIGHLIGHTS WARMING CLOUD TOPS, HINTING AT A NEAR-TERM
WEAKENING PERIOD AS THE APPROACHING DEEP-LAYER TROUGH TO THE WEST
IMPOSES 24KTS OF WESTERLY VERTICAL WIND SHEAR, BASED ON CIMSS
VERTICAL WIND SHEAR ANALYSIS. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON AN EARLIER 131710Z INTERNATIONAL SPACE
STATION TEMPEST 89Z IMAGE HIGHLIGHTING THE SPIRAL BANDING APPARENT
IN EIR, BUT ALSO REVEALING THE DEGRADING CONVECTION WITHIN THOSE
BANDS. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 51 KTS AT 131600Z
   CIMSS ADT: 35 KTS AT 131720Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE EASTWARD

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: TROPICAL STORM (TS) 06W WILL CONTINUE TO TRACK
NORTHWARD ON THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE FOR THE
NEST 12 HOURS. BETWEEN TAU 12-36, THE SYSTEM WILL GRADUALLY ROUND
THE RIDGE, TRACKING NORTHEASTWARD BY THE END OF THE FORECAST
PERIOD. THE APPROACHING TROUGH TO THE EAST WILL INCREASE VERTICAL
WIND SHEAR UNFAVORABLY BY TAU 12, LEADING TO A PERIOD OF WEAKENING
AS THE SYSTEM BECOMES EMBEDDED WITHIN THE JET. THE SYSTEM WILL
BEGIN EXTRATROPICAL TRANSITION AT TAU 12 DUE TO THE JET INTERACTION
 WITH SOME SUBTROPICAL FEATURES AS THE SYSTEM PASSES INTO COOL SEA
SURFACE TEMPERATURES BELOW 26C. AS EXTRATROPICAL TRANSITION CARRIES
ON, FRONTOGENESIS WILL OCCUR AS TS 06W BECOMES MORE BAROCLINIC. TS
07W IS ANTICIPATED TO BECOME FULLY EXTRATROPICAL BY THE END OF THE
FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
THAT TS 07W WILL TRACK NORTHWARD AND GRADUALLY NORTHEASTWARD
THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. THE CROSS-TRACK
SPREAD BY THE END OF THE FORECAST IS 175NM, LENDING TO THE FORECAST
CONFIDENCE. FEW, IF ANY, ENSEMBLE MEMBERS OF BOTH GEFS AND ECENS
TRACK OVER MAINLAND JAPAN. THE INTENSITY GUIDANCE IS IN GOOD
AGREEMENT THAT THE SYSTEM WILL SLOWLY WEAKEN AS EXTRATROPICAL
TRANSITION OCCURS AFTER TAU 12.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: HIGH//
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