Advisories

WDPN31 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 
020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.8N 137.5E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 348 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDING 
OF INTENSE DEEP CONVECTION WRAPPING TIGHTLY INTO THE COMPACT CORE OF 
TROPICAL STORM (TS) 24W (DUJUAN). WHILE THE DRY AIR MASS IS STILL 
SURROUNDING THE SYSTEM, CONVECTION IS BECOMING SLIGHTLY MORE 
ORGANIZED, ALBEIT LESS INTENSE AS EVIDENCED BY MODERATELY COLD CLOUD 
TOPS. SHORT-LIVED THUNDERSTORM FLARE-UPS OF -80 C AND COLDER OCCUR 
TRANSIENTLY. ENVIRONMENTAL ANALYSIS INDICATES A MARGINALLY FAVORABLE 
DEVELOPMENT REGIME, DRIVEN BY CONDUCIVE SEA SURFACE TEMPERATURES 
(SST) OF 28-29 C AND A STRONG POLEWARD OUTFLOW CHANNEL, UNDER A LOW 
VERTICAL WIND SHEAR (VWS) ENVIRONMENT OF 10-15 KTS. HOWEVER, 
DEVELOPMENT REMAINS HALTED DUE TO PERSISTENT DRY AIR ADVECTION 
ENTRAINING ALONG THE OUTER CIRCULATION FIELD. THE INITIAL POSITION IS 
DESIGNATED WITH HIGH CONFIDENCE, DEDUCED FROM CONVECTIVE WRAPPING 
INTO A VERY FAINT, IRREGULAR, AND SHORT-LIVED EYE FEATURE OBSERVED IN 
VISIBLE SATELLITE IMAGERY. THE INITIAL INTENSITY OF 60 KTS IS ALSO 
ASSESSED WITH HIGH CONFIDENCE, REFLECTING A FUSION OF SATELLITE 
DVORAK FIXES AND AUTOMATED OBJECTIVE ESTIMATES REPORTED BELOW.

INITIAL WIND RADII BASIS: A 200113Z METOP-C ASCAT PASS

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.5 - 55 KTS
   CIMSS SATCON: 69 KTS AT 200354Z
   CIMSS ADT: 49 KTS AT 200530Z
   CIMSS AIDT: 48 KTS AT 200530Z
   CIMSS D-MINT: 65 KTS AT 200355Z
   CIMSS D-PRINT: 66 KTS AT 200530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS DUJUAN HAS NOW CROSSED THE AXIS OF THE STR TO 
THE EAST AND IS EXPECTED TO BEGIN TURNING NORTHEASTWARD WITHIN THE 
NEXT 12 HOURS. THE CLOSEST POINT OF APPROACH (CPA) TO YOKOSUKA, 
JAPAN, IS ESTIMATED AT 63 NM AND IS EXPECTED TO OCCUR SHORTLY AFTER 
TAU 24. DURING THIS TIME, TS 24W IS FORECAST TO SLOWLY INTENSIFY 
UNDER MARGINALLY FAVORABLE ENVIRONMENTAL INFLUENCES, REACHING 70 KTS 
AROUND TAU 36. GLOBAL MODELS SHOW TS DUJUAN COCOONING FROM HOSTILE 
DRY AIR, WHILE TRANSITING OVER THE TAIL END OF THE WARM KUROSHIO 
CURRENT UNDER IMPROVING POLEWARD OUTFLOW DYNAMICS. AFTER TAU 48, 
EXTRATROPICAL TRANSITION (ETT) IS EXPECTED TO BEGIN AS WATERS BEGIN 
TO DRASTICALLY COOL, DRY-AIR ENTRAINMENT INCREASES, AND THE VERTICAL 
WIND SHEAR REACHES 30+ KTS. THE SYSTEM IS FORECAST TO BECOME FULLY 
EXTRATROPICAL PRIOR TO TAU 72 UPON ENCOUNTERING INTENSE UPPER-LEVEL 
WESTERLY JET WINDS ALOFT.

MODEL DISCUSSION: EXCELLENT AGREEMENT ENVELOPS THE DYNAMICAL MODEL 
TRACK PREDICTIONS, FEATURING A TIGHT 30 NM SPREAD AT THE CPA TO 
YOKOSUKA, WITH ALONG-TRACK TIMING VARIABILITY ESTIMATED AT 80 NM. 
GROUNDED IN THIS TIGHT GROUPING, THE OFFICIAL JTWC TRACK PROGNOSIS IS 
POSITIONED NEAR THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. IN 
TERMS OF INTENSITY, THE MODEL SUITES PROJECT STEADY-STATE INTENSITY 
OVER THE COMING 12 HOURS, FOLLOWED BY SLIGHT INTENSIFICATION. THE 
INTENSITY GUIDANCE SPREAD WIDENS REMARKABLY BY TAU 36, COVERING A 35 
KTS RANGE FROM 45 TO 80 KTS. ALTHOUGH STATISTICAL-DYNAMICAL GUIDANCE 
ARGUES FOR MONOTONIC CYCLOSIS, DETERMINISTIC MODELS (HAFS, COAMPS-TC, 
AND GFS) SUGGEST A TRANSITIONAL RE-DEEPENING TREND TO A PEAK 
INTENSITY OF 70 KTS AROUND TAU 36. REFLECTING THIS COHERENT TENDENCY, 
THE OFFICIAL JTWC INTENSITY FORECAST PARALLELS THE DYNAMICAL 
CONSENSUS WITH MEDIUM CONFIDENCE.

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