Advisories

WDPN31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.4N 141.7E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 42 NM NORTH-NORTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 24W RELATIVELY UNCHANGED FOR THE PAST SEVERAL HOURS. THE
COMMA SHAPE OF THE UPPER-LEVEL CONVECTION REMAINS PROMINENT AND
WELL-DEFINED. THE 181129Z ASCAT DATA REVEALS A PETITE CORE AND
ASYMMETRIC WIND FIELD. A LARGE SWATH OF STORM-FORCE WINDS PERSISTS
WITHIN THE NORTHERN SEMI-CIRCLE BUT DO NOT WRAP AROUND TO THE
SOUTHERN SEMI-CIRCLE, WHERE THE WIND SPEEDS ARE SIGNIFICANTLY
WEAKER. ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT,
CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WINDS SHEAR, WARM (28-29
C) SEA SURFACE TEMPERATURES, AND ROBUST POLEWARD OUTFLOW. THE
INITIAL POSITION AND INTENSITY ARE PLACED WITH HIGH CONFIDENCE
BASED ON THE AFOREMENTIONED ASCAT DATA.

INITIAL WIND RADII BASIS: ADJUSTED WIND RADII USING THE 181129Z
METOP-C ASCAT DATA

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T4.0 - 65 KTS
   CIMSS ADT: 49 KTS AT 181240Z
   CIMSS AIDT: 55 KTS AT 181240Z
   CIMSS D-PRINT: 67 KTS AT 181240Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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) IS FORECAST TO BEGIN TRACKING
NORTHWESTWARD IMMINENTLY WHILE IT REMAINS ON THE SOUTHWESTERN
PERIPHERY OF THE STEERING STR. BEGINNING AROUND TAU 12-24, TRACK
SPEEDS WILL SLOW AS 24W APPROACHES THE AXIS OF THE RIDGE. AT AROUND
TAU 36, 24W WILL CROSS THE RIDGE AXIS AND BEGIN ACCELERATING TO THE
NORTHEAST. DUJUAN WILL REMAIN ON A NORTHEASTWARD TRAJECTORY FROM
TAU 36-48 THROUGH THE END OF THE FORECAST PERIOD. AS 24W TRACKS
POLEWARD, IT WILL ENCOUNTER AN INCREASINGLY HOSTILE ENVIRONMENT. IT
IS EXPECTED TO CROSS THE 26C ISOTHERM JUST AFTER TAU 72, ALONG WITH
INCREASING VERTICAL WIND SHEAR TO 30-40 KTS, WHICH WILL INDUCE
SIGNIFICANT DRY AIR ENTRAINMENT. CONCURRENTLY WITH INCREASING SHEAR,
24W WILL BEGIN INTERACTING WITH THE UPPER-LEVEL JET PROMPTING WEAK
TEMPERATURE ADVECTION. IN RESPONSE TO THE HOSTILE ENVIRONMENT, 24W
IS FORECAST TO BEGIN EXTRATROPICAL TRANSITION AT TAU 72 AND
COMPLETE TRANSITION NO LATER THAN TAU 96. REGARDING INTENSITY, 24W
IS EXPECTED TO GRADUALLY INTENSIFY THROUGH ITS PEAK AT TAU 12-36.
24W IS FORECAST TO WEAKEN THEREAFTER AS A RESULT OF THE
ENVIRONMENT, ULTIMATELY COMPLETING EXTRATROPICAL TRANSITION AT
AROUND 50 KTS.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE REMAINS IN
TIGHT AGREEMENT THROUGHOUT THE DURATION OF THE FORECAST PERIOD,
SUPPORTING THE JTWC TRACK FORECAST WITH HIGH CONFIDENCE. RELIABLE
INTENSITY GUIDANCE IS COMING INTO BETTER AGREEMENT, AND ALL MODELS
NOW INDICATE A RELATIVELY STABLE INTENSITY UNTIL EXTRATROPICAL
TRANSITION COMMENCES. AS A RESULT, THE JTWC INTENSITY FORECAST IS
ASSESSED WITH OVERALL MEDIUM CONFIDENCE, WITH UNCERTAINTY STEMMING
FROM POSSIBLE UNFORECASTED INTENSITY FLUCTUATIONS BETWEEN 5-10 KTS
AS 24W APPROACHES THE RIDGE AXIS.

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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