Advisories

WDPN31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 24W (DUJUAN) WARNING NR 
019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.7N 137.5E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 411 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL 
STORM 24W (DUJUAN) WITH A SLIGHTLY MORE DISORGANIZED CONVECTIVE 
STRUCTURE NEAR THE INNER-CORE COMPARED TO 6 HOURS AGO. THE PREVIOUS 
COMPACT CENTRAL DENSE OVERCAST (CDO) FEATURE THAT WAS OBSCURING 
THE LOW-LEVEL CIRCULATION CENTER (LLCC) HAS SLIGHTLY FADED WITH 
WARMING CLOUD TOPS. A DEFINED BAND OF CONVECTION REMAINS SITUATED 
ALONG THE WESTERN SEMICIRCLE OF THE SYSTEM. A 192138Z WSFM 37 GHZ 
MICROWAVE IMAGE REVEALED A WEAKNESS IN THE SOUTHEASTERN QUADRANT OF 
THE MICROWAVE EYE, LIKELY DUE TO MID-LEVEL DRY AIR INTRUDING INTO 
THE VORTEX. A 192048Z RCM-2 SAR PASS SHOWED THAT THE CORE HAS CLEARLY 
DEGRADED OVER THE PAST 6 HOURS. THE RADIUS OF MAXIMUM WINDS HAS 
INCREASED AND THE MEASURED VMAX HAS DECREASED TO ABOUT 60 KTS. THE 
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE ANIMATED 
MSI AND EXTRAPOLATION FROM THE AFOREMENTIONED WSFM MICROWAVE IMAGE. 
THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED 
ON A BLEND OF THE RCM-2 SAR DATA, T4.0 DVORAK FIXES, AND THE CIMSS 
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 192048Z RCM-2 SAR DATA 

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 SATCON: 64 KTS AT 192107Z
   CIMSS ADT: 51 KTS AT 192330Z
   CIMSS AIDT: 45 KTS AT 192330Z
   CIMSS D-MINT: 66 KTS AT 192106Z
   CIMSS D-PRINT: 64 KTS AT 192330Z

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: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

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

FORECAST DISCUSSION: AFTER TRACKING VERY SLOWLY FROM 191800Z TO 
192200Z, 24W LOOKS TO HAVE STARTED ON ITS NORTHWARD TRACK ALONG 
THE WESTERN PERIPHERY OF THE STEERING RIDGE. THE NORTHWARD TRACK 
IS EXPECTED TO PERSIST THROUGH TAU 12 AS THE SYSTEM ROUNDS THE 
RIDGE AXIS. AFTER TAU 12, 24W WILL BEGIN TO TURN NORTHEASTWARD 
WITH INCREASING TRACK SPEEDS. THE CPA TO YOKOSUKA IS FORECAST TO 
OCCUR JUST BEFORE TAU 36, AND REMAINS CONSISTENT WITH THE PREVIOUS 
FORECAST. FOLLOWING TAU 36, 24W WILL ACCELERATE EAST-NORTHEASTWARD 
AS THE SYSTEM STARTS TO INTERACT 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 THROUGH 
TAU 12-24 DUE TO THE STRONG POLEWARD OUTFLOW FIGHTING AGAINST DRY 
AIR AND INCREASING SOUTHERLY VERTICAL WIND SHEAR. AFTERWARD, 24W IS 
FORECAST TO SLIGHTLY INTENSIFY AS IT PASSES BY EAST OF TOKYO, DRIVEN 
PRIMARILY BY AN EXCEPTIONAL POLEWARD OUTFLOW CHANNEL. THE POLEWARD 
OUTFLOW WILL BE SUPPORTED BY A STRONG 150+ KNOT JET MAXIMUM PLACED 
TO THE NORTHEAST OF HOKKAIDO. AFTER TAU 48, SIGNIFICANT DRY AIR 
ENTRAINMENT AND WESTERLY VERTICAL WIND SHEAR WILL BEGIN TO HEAVILY 
IMPACT THE SYSTEM. ADDITIONALLY, SEA SURFACE TEMPERATURES WILL COOL 
ONCE 24W CLEARS THE KUROSHIO CURRENT. AS A RESULT, 24W IS FORECAST 
TO WEAKEN AS IT TRANSITIONS INTO A COLD-CORE CYCLONE.

MODEL DISCUSSION: MODEL TRACK GUIDANCE REMAINS IN GOOD AGREEMENT
THROUGHOUT THE FORECAST PERIOD WITH A CROSS-TRACK SPREAD OF 60 NM 
AT TAU 48 AND 120 NM AT TAU 72. ALONG-TRACK SPREAD DOES INCREASE 
A BIT AFTER TAU 24, 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 24 AND THEN SLIGHTLY FASTER 
THROUGH TAU 72 WITH HIGH CONFIDENCE. INTENSITY GUIDANCE GENERALLY 
AGREES ON A STEADY INTENSITY THROUGH TAU 12 FOLLOWED BY MARGINAL 
INTENSIFICATION AND WEAKENING THEREAFTER. COAMPS-TC HAS BECOME THE 
MOST AGGRESSIVE MODEL THIS RUN, DEPICTING A PEAK INTENSITY OF 80 KTS. 
NOTABLY, HAFS-A IS LESS AGGRESSIVE THIS RUN AND NOW SHOWS A PEAK 
INTENSITY OF 70 KTS. THE JTWC INTENSITY FORECAST IS SET NEAR THE 
CONSENSUS WITH MEDIUM CONFIDENCE.

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