Advisories

WDPN31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.9N 142.9E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 109 NM NORTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 24W AS A WELL-DEFINED STORM WITH A PROMINENT COMMA CLOUD
AND AN EXPANDING CENTRAL DEEP OVERCAST FEATURE. LOWER-LEVEL CLOUDS 
TIGHTLY WRAP INTO THE FULLY OBSCURED LOW-LEVEL CIRCULATION CENTER 
(LLCC) WHILE THE UPPER-LEVEL DEEP CONVECTION IS JUST BEGINNING TO 
WRAP INTO THE CENTER. 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 IS PLACED WITH MEDIUM CONFIDENCE
BASED ON LOW-LEVEL CLOUD BANDS WRAPPING INTO THE OBSCURED LLCC. THE
INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE SLIGHTLY IMPROVED APPEARANCE IN ANIMATED IMAGERY,
SUPPORTED BY THE AGENCY DVORAK FIXES AND AUTOMATED CIMSS INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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: T3.5 - 55 KTS
   CIMSS SATCON: 58 KTS AT 180600Z
   CIMSS ADT: 55 KTS AT 180630Z
   CIMSS AIDT: 55 KTS AT 180630Z
   CIMSS D-MINT: 46 KTS AT 180336Z
   CIMSS D-PRINT: 49 KTS AT 180630Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 (DJUAN) IS FORECAST TO CONTINUE
TRACKING NORTHWESTWARD WHILE IT REMAINS ON THE SOUTHWESTERN
PERIPHERY OF THE STEERING STR. BEGINNING AROUND TAU 24, TRACK
SPEEDS WILL SLOW AS IT APPROACHES THE AXIS OF THE RIDGE. BETWEEN
TAU 24-48, 24W WILL ROUND THE RIDGE AXIS AND BEGIN TO ACCELERATE
NORTHEASTWARD. DUJUAN WILL REMAIN ON A NORTHEASTWARD TRAJECTORY
FROM TAU 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 BETWEEN TAU 72-96.
SIMULTANEOUSLY, VERTICAL WIND SHEAR IS EXPECTED TO CLIMB TO 30-40
KTS, WHICH WILL INDUCE SIGNIFICANT DRY AIR ENTRAINMENT, CONCURRENT
WITH UPPER-LEVEL JET INTERACTION THAT WILL INDUCE WEAK TEMPERATURE
ADVECTION. IN RESPONSE TO THE HOSTILE ENVIRONMENT, 24W IS FORECAST
TO BEGIN EXTRATROPICAL TRANSITION AT TAU 96 AND COMPLETE TRANSITION
NO LATER THAN TAU 120. REGARDING INTENSITY, 24W IS EXPECTED TO
GRADUALLY INTENSIFY THROUGH ITS PEAK AT TAU 24-48. 24W IS FORECAST
TO WEAKEN THEREAFTER AS A RESULT OF THE ENVIRONMENT, ULTIMATELY
COMPLETING EXTRATROPICAL TRANSITION AT 45-50 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
FOR THE NEXT 48 HOURS. 

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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