WDPN31 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (NAKRI) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.7N 130.6E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 151 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION TILTED TO THE SOUTH OF THE LOW-LEVEL CIRCULATION CENTER
(LLCC) OF TROPICAL STORM (TS) 29W. LOW NORTHERLY VERTICAL WIND
SHEAR INTRODUCES DRY AIR, EXPOSING THE LOW-LEVEL CLOUD BANDING.
EARLIER, AN 101720Z NOAA-20 ATMS 89GHZ IMAGE HIGHLIGHTING THE
ASYMMETRIC UPPER-LEVEL STRUCTURE. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON THE LOW-LEVEL BANDING EVIDENT ALONG
THE NORTHERN PERIPHERY OF THE CIRCULATION IN ANIMATED EIR, AND
SURFACE OBSERVATIONS BETWEEN MINAMIDAITOJIMA AND OKINAWA. THE
INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT
BETWEEN TWO SUBTROPICAL RIDGES

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 44 KTS AT 101721Z
   CIMSS ADT: 37 KTS AT 101730Z
   CIMSS AIDT: 37 KTS AT 101730Z
   CIMSS D-MINT: 30 KTS AT 101926Z
   CIMSS D-PRINT: 30 KTS AT 101900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 SLOWLY BREAK OUT OF THE CURRENT
COMPLEX STEERING ENVIRONMENT AS THE SUBTROPICAL RIDGE POSITIONED
WEST OF THE SYSTEM WEAKENS. AS A RESULT, TS 29W WILL COME UNDER THE
PRIMARY STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO THE EAST,
INITIALLY CURVING NORTHEASTWARD WITHIN THE FIRST 24 HOURS. AS THE
SYSTEM CURVES EAST-NORTHEASTWARD AFTER TAU 36, TS 29W WILL INCREASE
THE TRACK SPEED TO 19KTS BY THE END OF THE FORECAST AS THE SYSTEM
APPROACHES THE SUBTROPICAL JET. EXTRATROPICAL TRANSITION WILL BEGIN
AFTER TAU 72 AS TS 29 BECOMES ASYMMETRIC AND BEGINS TO DEVELOP
FRONTS, AND WILL COMPLETE EXTRATROPICAL TRANSITION BY TAU 96 AFTER 
BECOMING A FULLY FRONTAL COLD-CORE SYSTEM. THE ENVIRONMENT WILL BE 
FAVORABLE FOR DEVELOPMENT. VERTICAL WIND SHEAR WILL REMAIN LOW AND 
FAVORABLE UNTIL TAU 72 WHEN SHEAR IS ANTICIPATED TO BE ABOVE 20KTS. 
SEA SURFACE TEMPERATURES WILL REMAIN HIGH AND FAVORABLE UNTIL THE
SYSTEM PASSES NORTH OF THE KUROSHIO CURRENT BETWEEN TAU 48-72.
OUTFLOW WILL REMAIN FAVORABLE AND STRONGEST POLEWARD DUE TO THE JET
TO THE NORTH UNTIL THE APPROACH OF THE SYSTEM TO THE JET PRODUCES
THE AFOREMENTIONED UNFAVORABLE SHEAR. AFTER REACHING A PEAK
INTENSITY OF 80KTS AT TAU 48, THE SYSTEM IS ANTICIPATED TO WEAKEN
TO 50KTS AS AN EXTRATROPICAL SYSTEM BY THE END OF THE FORECAST
PERIOD. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
THAT TS 29W WILL ROUND THE NORTHERN PERIPHERY OF THE SUBTROPICAL
RIDGE TO THE EAST, INCREASING TRACK SPEED AS THE SYSTEM APPROACHES
THE JET. THE CROSS-TRACK SPREAD BY THE END OF THE FORECAST PERIOD
IS 174NM, SPECIFICALLY AS THE SYSTEM BECOMES EXTRATROPICAL. THE
INTENSITY GUIDANCE IS TRENDING HIGHER AND IS SHOWING STRONGER
INDICATIONS OF RAPID INTENSIFICATION POTENTIAL WITHIN THE
EARLY-TERM FORECAST WITH PEAK INTENSITIES BETWEEN 60-110KTS.
WHETHER OR NOT 29W GETS ITSELF TOGETHER IN THE EARLY TERM WILL
INFLUENCE THE LATE-TERM FORECAST, AND WITH THE LARGE SPREAD OF
SOLUTIONS, THERE IS UNCERTAINTY IN THE INTENSITY FORECAST.

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