Advisories

WDPN31 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (DUJUAN) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.5N 137.7E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 420 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON 
24W (DUJUAN) WITH A HIGHLY COMPACT LOW-LEVEL CIRCULATION CENTER (LLCC) 
THAT IS OBSCURED BY A SMALL CENTRAL DENSE OVERCAST (CDO). THE COLDEST 
CLOUD TOPS ARE MEASURED TO BE COLDER THAN -80 C CLOSE TO THE ASSESSED 
CENTER. ADDITIONALLY, A TIGHT CURVED BAND OF DEEP CONVECTION HAS 
FORMED OVER THE PAST FEW HOURS ALONG THE NORTHERN PORTION OF THE 
CIRCULATION. A LACK OF HIGH-RESOLUTION MICROWAVE IMAGERY CAUSES THERE 
TO BE SOME UNCERTAINTY IN THE STRUCTURE OF THE CORE AND POTENTIAL 
VORTEX TILT. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE 
BASED PRIMARILY ON THE ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 
65 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK 
FIXES AND CIMSS INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL 
ANALYSIS INDICATES THAT 24W REMAINS PLACED WITHIN A MARGINALLY 
FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW ALOFT, 
LOW (10-15 KTS) SOUTHERLY VERTICAL WIND SHEAR, DRY AIR ENTRAINMENT, 
AND WARM (28-29 C) SEA SURFACE TEMPERATURES. 

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: THE WESTERN PERIPHERY OF A SUBTROPICAL 
RIDGE (STR) CENTERED TO THE EAST OF HONSHU

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 191800Z
   CIMSS AIDT: 51 KTS AT 191800Z
   CIMSS D-MINT: 67 KTS AT 191639Z
   CIMSS D-PRINT: 66 KTS AT 191800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

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 IMMINENTLY BEGIN A 
NORTHWARD TURN AS IT STARTS TO ROUND THE STEERING RIDGE AXIS. THE
NORTHWARD TRACK IS THEN EXPECTED TO PERSIST THROUGH TAU 18-24 BEFORE 
THE SYSTEM STARTS TO ACCELERATE NORTHEASTWARD ALONG THE NORTHWESTERN 
PERIPHERY OF THE RIDGE. THE TIMING OF THE CPA TO YOKOSUKA IS FORECAST 
TO OCCUR JUST AFTER TAU 36, AND REMAINS LARGELY CONSISTENT WITH THE 
PREVIOUS FORECAST. AFTER TAU 36, TRACK SPEEDS WILL BEGIN TO 
SIGNIFICANTLY INCREASE AS THE SYSTEM INTERACTS WITH THE STRONG MID-
LATITUDE WESTERLIES. EXTRATROPICAL TRANSITION IS FORECAST TO BEGIN AT 
TAU 60 WITH COMPLETION AROUND TAU 72, ONCE 24W BECOMES FURTHER 
EMBEDDED UNDERNEATH THE JET AND THERMAL ADVECTION INCREASES. IN TERMS 
OF INTENSITY, 24W IS FORECAST TO MAINTAIN ITS CURRENT INTENSITY OF 65 
KTS THROUGH TAU 36 DUE TO THE STRONG POLEWARD OUTFLOW FIGHTING AGAINST 
DRY AIR AND INCREASING SOUTHERLY VERTICAL WIND SHEAR. FROM TAU 48 TO 
TAU 60, A BRIEF PERIOD OF INTENSIFICATION IS FORECAST TO OCCUR DUE TO 
24W TAPPING INTO AN EXTREME POLEWARD OUTFLOW CHANNEL, SUPPORTED BY A 
150+ KNOT JET MAXIMUM PLACED NORTHEAST OF HOKKAIDO. AFTER TAU 60, 24W 
IS FORECAST TO BEGIN WEAKENING DUE TO COOLING SEA SURFACE 
TEMPERATURES, VERY HIGH (OVER 50 KTS) WESTERLY VERTICAL WIND SHEAR, 
AND SIGNIFICANT DRY AIR ENTRAINMENT.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGHOUT 
THE FORECAST PERIOD WITH A CROSS-TRACK SPREAD OF ABOUT 50 NM AT TAU 48 
AND 105 NM AT TAU 72. ALONG-TRACK SPREAD DOES INCREASE A BIT AFTER TAU 
48 WITH GFS BEING THE NOTABLE SLOW OUTLIER AMONG THE GUIDANCE. 
OVERALL, THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL 
CONSENSUS THROUGH TAU 48 AND THEN SLIGHTLY FASTER THROUGH TAU 72 WITH 
HIGH CONFIDENCE. INTENSITY GUIDANCE GENERALLY AGREES ON A STEADY 
INTENSITY THROUGH TAU 36, FOLLOWED BY BRIEF INTENSIFICATION FROM TAU 
48-60 AND WEAKENING THEREAFTER. HAFS-A HAS BECOME A SLIGHT OUTLIER, 
DEPICTING A PEAK INTENSITY OF 90 KTS AT TAU 48. THIS IS A POSSIBILITY 
IF 24W IS ABLE TO MAINTAIN A COMPACT CORE THAT FIGHTS OFF THE DRY AIR 
INTRUSION AND SOUTHERLY SHEAR. AS IT STANDS, THE JTWC INTENSITY 
FORECAST IS PLACED NEAR THE MODEL CONSENSUS WITH MEDIUM CONFIDENCE.

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