Advisories

WDPN31 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (DUJUAN) WARNING NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.2N 139.7E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 121 NM NORTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 24W 
(DUJUAN) WITH A HIGHLY COMPACT LOW-LEVEL CIRCULATION CENTER (LLCC) 
THAT IS MOSTLY OBSCURED BY SPIRAL CONVECTIVE BANDING TIGHTLY WRAPPING 
INTO THE CENTER. DRY AIR CAN BE SEEN WRAPPING INTO THE CORE OF THE 
VORTEX FROM THE WEST, CREATING A WEDGE OF SUPPRESSED CONVECTIVE 
ACTIVITY. A 182041Z RCM-2 SAR PASS REVEALED AN EXTREMELY COMPACT 
INNER-CORE WITH A RADIUS OF MAXIMUM WINDS AROUND 5 NM. THE VMAX WAS 
MEASURED TO BE 77 KTS LOCATED WITHIN THE NORTHERN PORTION OF THE LLCC. 
THE INITIAL INTENSITY OF 65 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED 
ON THE SLIGHT HIGH BIAS OF THE RCM SENSOR AND IS SUPPORTED BY THE 
AGENCY DVORAK FIXES OF T3.5-4.0. THE INITIAL POSITION AND WIND RADII 
ARE BOTH PLACED WITH HIGH CONFIDENCE BASED ON A TIMELY 182332Z METOP-B 
ASCAT BULLSEYE PASS. ENVIRONMENTAL ANALYSIS INDICATES THAT 24W IS IN A 
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD 
OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, DRY AIR 
ENTRAINMENT, AND WARM (28-29 C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: 182041Z RCM-2 SAR DATA AND 182332Z
METOP-B ASCAT DATA

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A 
SUBTROPICAL RIDGE (STR) POSITIONED EAST OF HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T4.0 - 65 KTS
   CIMSS ADT: 43 KTS AT 190000Z
   CIMSS AIDT: 49 KTS AT 190000Z
   CIMSS D-MINT: 61 KTS AT 182300Z
   CIMSS D-PRINT: 50 KTS AT 190000Z

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: HIGH

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 24W IS FORECAST TO TRACK NORTHWESTWARD, ALONG 
THE SOUTHWESTERN PERIPHERY OF THE STR POSITIONED TO THE EAST OF HONSHU 
THROUGH TAU 24. THE SYSTEM WILL THEN START ON A NORTHWARD TRACK AS IT 
ROUNDS THE RIDGE AXIS THROUGH TAU 48. THE CPA TO YOKOSUKA IS FORECAST 
TO OCCUR NEAR TAU 60 AS 24W BEGINS TO ACCELERATE NORTHEASTWARD.  
FOLLOWING TAU 60, THE SYSTEM IS FORECAST TO BEGIN EXTRATROPICAL 
TRANSITION WITH QUICKLY INCREASING TRACK SPEEDS AS IT BEGINS TO 
INTERACT WITH THE STRONG MID-LATITUDE WESTERLIES AND ASSOCIATED 
BAROCLINIC ZONE. EXTRATROPICAL TRANSITION IS FORECAST TO COMPLETE BY 
TAU 96, ONCE THE VORTEX ENTERS COLD (22-23 C) SEA SURFACE 
TEMPERATURES, HIGH (OVER 50 KTS) SHEAR, AND INCREASING THERMAL 
ADVECTION. IN TERMS OF INTENSITY, 24W IS FORECAST TO MAINTAIN ITS 
CURRENT INTENSITY OF 65 KTS THROUGH TAU 60 AS DRASTICALLY IMPROVING 
POLEWARD OUTFLOW FIGHTS WITH INCREASING SOUTHERLY SHEAR AND THE 
PERSISTENT DRY AIR ENTRAINMENT. AFTER TAU 60, THE VERTICAL WIND SHEAR 
AND DRY AIR WILL OVERWHELM THE VORTEX, CAUSING 24W TO WEAKEN THROUGH 
THE REMAINDER OF THE FORECAST PERIOD.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN VERY GOOD AGREEMENT 
THROUGH TAU 72 WITH A CROSS-TRACK SPREAD MEASURED TO BE ABOUT 90 NM. 
AFTER TAU 72, ALONG-TRACK SPREAD BEGINS TO INCREASE DUE TO VARIATIONS 
IN THE INTERACTION WITH THE UPPER-LEVEL JET. THE JTWC TRACK FORECAST 
IS PLACED NEAR THE MULTI-MODEL CONSENSUS THROUGH TAU 72 AND THEN 
CLOSER TO THE ECMWF THROUGH TAU 96. INTENSITY GUIDANCE GENERALLY 
AGREES ON A STEADY INTENSITY THROUGH TAU 60 FOLLOWED BY WEAKENING 
THROUGH TAU 96. HAFS-A AND GFS SHOW A BRIEF INTENSIFICATION TO 75-80 
KTS ONCE THE ROBUST POLEWARD OUTFLOW CHANNEL SETS UP BEFORE WEAKENING, 
WHICH IS NOT OUT OF THE REALM OF POSSIBILITY. AS A RESULT, THE JTWC 
INTENSITY FORECAST IS PLACED CLOSE TO THE CONSENSUS WITH OVERALL 
MEDIUM CONFIDENCE.

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