Advisories

WDPN31 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.9N 150.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 530 NM EAST-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 29 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 24W (DUJUAN) STAGNATED IN DEVELOPMENT. THE CORE REMAINS
COMPACT, ASYMMETRIC, AND FULLY EMBEDDED IN THE SOUTHERN END OF A
SURFACE TROUGH. THE NORTHERN END OF THE TROUGH OCCASIONALLY
PRODUCES SHORT-LIVED SPINNERS AND MAINTAINS PERSISTENT DEEP
CONVECTION ALONG THE SHARP TROUGH AXIS. ENVIRONMENTAL ANALYSIS
REVEALS A FAVORABLE ENVIRONMENT, CHARACTERIZED BY WARM (29-30 C)
SEA SURFACE TEMPERATURES, AMPLE MOISTURE SURROUNDING THE COMPACT
CORE, AND GOOD DIVERGENCE, OFFSET SLIGHTLY BY LOW TO MODERATE
(15-20 KTS) VERTICAL WIND SHEAR. THE INITIAL POSITION IS PLACED
WITH LOW CONFIDENCE BASED ON MINIMAL LOWER-LEVEL CLOUD BANDING
OBSERVED UNDER THE NORTHERN EDGE OF THE CENTRAL DEEP OVERCAST. THE
INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE CIMSS AUTOMATED INTENSITY ESTIMATES AND AGENCY DVORAK
FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE SOUTHERN EXTENSION OF A SUBTROPICAL
RIDGE CENTERED FAR TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 50 KTS AT 170307Z
   CIMSS ADT: 41 KTS AT 170220Z
   CIMSS AIDT: 37 KTS AT 170220Z
   CIMSS D-MINT: 50 KTS AT 170308Z
   CIMSS D-PRINT: 44 KTS AT 170500Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: MEDIUM
   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 24W IS CURRENTLY TRACKING NORTHWARD AND
WILL BEGIN TO CURVE TO THE NORTHWEST WITHIN THE NEXT FEW HOURS. 24W
WILL TRACK NORTHWESTWARD THROUGH TAU 48 WHILE THE SOUTHWARD
EXTENSION OF THE STEERING RIDGE RETREATS. AS DUJUAN APPROACHES THE
RIDGE AXIS, SPEED OF ADVANCE WILL SLOW PARTICULARLY BETWEEN TAU
24-48. 24W WILL ROUND THE RIDGE AXIS AROUND TAU 60 AND BEGIN
ACCELERATING TO THE NORTHEAST FOR THE REMAINDER OF THE FORECAST
PERIOD. AROUND TAU 96, DUJUAN IS EXPECTED TO CROSS THE 26C ISOTHERM
AND ENCOUNTER AN INCREASINGLY HOSTILE ENVIRONMENT CHARACTERIZED BY
HIGH (30-40 KTS) VERTICAL WIND SHEAR, DRY AIR, AND JET INTERACTION
INDUCING WEAK THERMAL ADVECTION. REGARDING INTENSITY, 24W IS
EXPECTED TO VERY GRADUALLY INTENSIFY THROUGH ITS PEAK AT TAU 60.
THE ENVIRONMENT IS EXPECTED TO REMAIN RELATIVELY CONSISTENT THROUGH
TAU 60, THOUGH THE SLIGHTLY ELEVATED WIND SHEAR MAY PROHIBIT
SIGNIFICANT INTENSIFICATION OR EVEN STAGNATE INTENSIFICATION
ENTIRELY. WIND SHEAR IS CURRENTLY NOT EXPECTED TO HAVE A MAJOR
IMPACT ON INTENSITY, AND 24W IS STILL FORECAST TO REACH TYPHOON
STRENGTH. THE MAIN INHIBITOR TO SIGNIFICANT INTENSIFICATION REMAINS
THE STORM'S ASYMMETRIC CORE. AROUND TAU 48-60, VERTICAL WIND SHEAR
IS EXPECTED TO ABATE SLIGHTLY AND DIVERGENCE ALOFT IS EXPECTED TO
INCREASE, CONTRIBUTING TO THE INTENSIFICATION PERIOD AS 24W
APPROACHES THE RIDGE AXIS. DUJUAN WILL REMAIN AT TROPICAL-STORM
STRENGTH WHILE IT UNDERGOES AND COMPLETES EXTRATROPICAL TRANSITION.
24W IS FORECAST TO BEGIN EXTRATROPICAL TRANSITION BETWEEN TAU 96
AND COMPLETE TRANSITION AFTER TAU 120.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE REMAINS IN
STRONG AGREEMENT THROUGH THE ENTIRETY OF THE FORECAST PERIOD,
SUPPORTING THE JTWC TRACK FORECAST WITH HIGH CONFIDENCE. RELIABLE
DETERMINISTIC INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT IN A
RELATIVELY STABLE INTENSITY THROUGH TAU 120. HOWEVER, SEVERAL JTWC
RAPID INTENSIFICATION AIDS HAVE TRIGGERED, INDICATING A POSSIBILITY
FOR RAPID INTENSIFICATION IN THE NEXT 24-40 HOURS. JTWC HAS
DETERMINED 24W HAS A LOW CHANCE OF RAPID INTENSIFICATION, AND THE
INTENSITY FORECAST IS IN CLOSE ALIGNMENT WITH THE MULTI-MODEL
CONSENSUS AND THE FOLLOWING GLOBAL AND MESOSCALE MODELS: GFS,
COAMPS, HAFS, AND HWRF. AS A RESULT OF THE UNCERTAINTY, THE JTWC
INTENSITY FORECAST IS ASSESSED WITH OVERALL MEDIUM CONFIDENCE. 

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