Advisories

WDPN31 PGTW 171500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.8N 148.6E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 404 NM EAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 27 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 24W (DUJUAN) AS A HIGHLY COMPACT SYSTEM STILL EMBEDDED
WITHIN THE ELONGATED SURFACE TROUGH. SPIRAL BANDS OF DEEP CONVECTION 
ARE NEWLY FORMING, INDICATING 24W IS ORGANIZING AND INTENSIFYING. 
ANIMATED BRIGHTNESS TEMPERATURE REVEALS THE UPPER-LEVEL CLOUD TOPS ARE 
STRUGGLING TO REMAIN COLDER THAN -80C. THE 170812Z WSFM SUITE OF 
MICROWAVE IMAGES SUGGESTED THAT 24W WAS POORLY ORGANIZED THROUGHOUT 
THE VERTICAL COLUMN, WITH A WEAKLY DEFINED AND PARTIALLY OPEN 
MICROWAVE EYE IN THE LOWER LEVELS AND DISJOINTED UPPER-LEVEL 
CONVECTION. HOWEVER, THE MORE RECENT 171148Z ASCAT DATA REVEALS 24W IS 
APPROACHING TYPHOON STRENGTH, WITH A HANDFUL OF 60 KT WIND BARBS IN 
THE NORTHEASTERN QUADRANT. ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE 
ENVIRONMENT, CHARACTERIZED BY MODERATE TO HIGH (20-25 KTS) VERTICAL 
WIND SHEAR, WARM (28-29 C) SEA SURFACE TEMPERATURES, AND GOOD 
DIVERGENCE ALOFT. THE INITIAL POSITION AND INTENSITY ARE PLACED WITH 
HIGH CONFIDENCE BASED ON THE AFOREMENTIONED 171148Z ASCAT DATA.

INITIAL WIND RADII BASIS: ADJUSTED THE WESTERN WIND RADII USING THE
170809Z RCM-3 SAR DATA.

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) 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 ADT: 51 KTS AT 171140Z
   CIMSS AIDT: 44 KTS AT 171140Z
   CIMSS D-PRINT: 41 KTS AT 171210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 24W (DUJUAN) WILL TRACK NORTHWESTWARD THROUGH 
TAU 48 WHILE THE SOUTHWARD EXTENSION OF THE STEERING RIDGE RETREATS 
AND THE STEERING STR SHIFTS EQUATORWARD. AS DUJUAN APPROACHES THE 
RIDGE AXIS, SPEED OF ADVANCE WILL SLOW PARTICULARLY BETWEEN TAU 24-60. 
24W WILL ROUND THE RIDGE AXIS JUST BEFORE 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 48-60. 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 AS OTHER ENVIRONMENTAL 
FACTORS REMAIN FAVORABLE. 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 AROUND 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; THOUGH THEY DID NOT ACCURATELY CAPTURE THE 
RECENT PERIOD OF INTENSIFICATION AND ARE CURRENTLY UNDERESTIMATING 
DUJUAN'S INTENSITY. SEVERAL JTWC RAPID INTENSIFICATION AIDS HAVE 
TRIGGERED, INDICATING A POSSIBILITY FOR RAPID INTENSIFICATION IN THE 
NEXT 24-36 HOURS. THE JTWC INTENSITY FORECAST IS IN CLOSE ALIGNMENT 
WITH THE EXPERIMENTAL GOOGLE DEEPMIND. AS A RESULT OF THE HIGH DEGREE 
OF UNCERTAINTY, THE JTWC INTENSITY FORECAST IS ASSESSED WITH OVERALL 
LOW CONFIDENCE. 

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