WDPN31 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (NAKRI) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.3N 131.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 252 NM SOUTH-SOUTHEAST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS BUILDING
DEEP CONVECTION AND A TILTED STRUCTURE OF TROPICAL STORM (TS) 29W.
UNFORTUNATELY, THERE IS LIMITED AGENCY AND OBJECTIVE FIX SUPPORT
DUE TO A HIMAWARI-9 OUTAGE. HOWEVER, JMA DOPPLER RADAR DATA
VERIFIED THE LOW-LEVEL POSITIONING OF TS 29W REVEALING WELL-DEFINED
CENTRAL STRUCTURE AND CLOUD BANDING WRAPPING INTO THE CENTER. A
DEEP-LAYER RIDGE TO THE WEST APPLIES PRESSURE TO THE SYSTEM,
INDUCING 10-15KTS OF VERTICAL WIND SHEAR AND BOUNDING THE WESTERN
FLANK OF THE SYSTEM WITH CONTINENTAL DRY AIR SOURCED FROM MAINLAND
CHINA. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE AFOREMENTIONED ANIMATED EIR AND RADAR LOOP. THE INITIAL
INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY FIXES BELOW WHILE SUPPORTED BY A 56KT ASSESSMENT MADE BY
CIMSS MICROWAVE SOUNDERS.

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
   RCTP: T3.0 - 45 KTS
   KNES: T4.0 - 65 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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: TS 29W WILL REMAIN UNDER THE STEERING
INFLUENCE OF THE SUBTROPICAL RIDGE TO THE EAST, GRADUALLY CURVING
FROM A NORTHEASTWARD TRACK TO A EAST-NORTHEASTWARD TRACK BY THE END
OF THE FORECAST PERIOD. AS TS 29W APPROACHES THE ZONAL FLOW OF THE
SUBTROPICAL JET TO THE NORTH, THE SYSTEM WILL EXIT THE SUPPORTIVE
WARM SEA SURFACE TEMPERATURES OF THE KUROSHIO CURRENT WHILE ALSO
BECOMING FRONTAL AND COLD-CORE. TS 19W WILL BECOME FULLY
EXTRATROPICAL BY TAU 72. THE ENVIRONMENT WILL REMAIN SUPPORTIVE FOR
INTENSIFICATION FOR THE NEXT 36 HOURS AS THE SYSTEM INTENSIFIES TO
A PEAK INTENSITY OF 80KTS. VERTICAL WIND SHEAR WILL REMAIN WESTERLY
AND LOW BETWEEN 10-15KTS AS THE SYSTEM BECOMES EMBEDDED IN THE
ZONAL UPPER-LEVEL FLOW JUST SOUTH OF THE SUBTROPICAL JET. SEA
SURFACE TEMPERATURES WILL REMAIN WARM UNTIL THE SYSTEM PASSES SOUTH
OF TOKYO AND TRACKS NORTH OF THE KUROSHIO CURRENT. OUTFLOW WILL
REMAIN FAVORABLE BOTH POLEWARD, ENCOURAGED BY THE JET TO THE NORTH,
AND EQUATORWARD, ENCOURAGED BY THE UPPER-LEVEL RIDGE TO THE WEST.
WEAKENING AFTER TAU 36 WILL COMMENCE DUE TO INFLUENCE TO THE
SUBTROPICAL JET AS VERTICAL WIND SHEAR BECOMES UNFAVORABLY HIGH. BY
THE END OF THE FORECAST PERIOD, TS 29W WILL HAVE WEAKENED TO 55KTS
AS AN EXTRATROPICAL CYCLONE. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG
AGREEMENT THAT TS 29W WILL CURVE ALONG THE NORTHERN PERIPHERY OF
THE SUBTROPICAL RIDGE TO THE EAST. THE CROSS-TRACK SPREAD BY TAU 72
IS 80NM, LENDING HIGH CONFIDENCE TO THE TRACK FORECAST. THE
INTENSITY GUIDANCE HAS SLIGHTLY MORE SPREAD, INDICATING PEAK
INTENSITIES BETWEEN 65-90KTS FROM TAU 36-60, BASED ON A VARIETY OF
TRACK SPEEDS. THE JTWC FORECAST LIES CLOSELY TO THE CONSENSUS,
COAMPS-TC, AND HWRF, WHICH ALL HOVER AROUND A PEAK INTENSITY OF
80KTS. HAFS-A LIES ON THE HIGHER END AND LATER IN THE FORECAST
PERIOD, 90KTS AT TAU 60, AND GFS ANTICIPATES A LOWER PEAK OF 65 AT
TAU 36.

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