WDPN31 PGTW 282100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 01W (EWINIAR) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.8N 129.5E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 241 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 20 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) DEFINED BY CURVED
CLOUD LINES WRAPPING INTO THE WESTERN EDGE OF THE OBSERVED FLARING
CONVECTION WITH WARMING TOPS OVER THE LAST FEW HOURS. MODERATE
VERTICAL WIND SHEAR (VWS) REMAINS EVIDENT ALONG THE NORTHWESTERN
PERIPHERY OF THE UPPER-LEVEL CIRRUS SHIELD, ILLUSTRATED BY A STRONG
THERMAL GRADIENT ALOFT AND CONTINUED STRIATIONS ON THE EASTERN
OUTSKIRTS OF THE SYSTEM. MODERATE DUAL-CHANNEL UPPER-LEVEL OUTFLOW
HAS BEEN APPARENT THROUGHOUT THE PREVIOUS SIX HOURS, WITH AMPLIFIED
POLEWARD INFLUENCE FROM A SOUTHWARD EXTENDING LONGWAVE TROUGH, AND
SOUTHWARD CHANNEL OVER THE PHILIPPINE SEA. THE INITIAL POSITION FOR
TYPHOON (TY) 01W IS PLACED WITH HIGH CONFIDENCE BASED ON A 281700Z
ATMS 88.2 GHZ IMAGE ILLUSTRATING SHALLOW LOW-LEVEL CLOUD LINES
WRAPPING INTO THE WESTERN EDGE OF THE CURVED CONVECTIVE BAND. THE
INITIAL INTENSITY OF 75 KTS WAS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE SUBJECTIVE AGENCY ESTIMATES LISTED BELOW AND AN
EARLIER RCM-3 SAR PASS SHOWING A SWATH OF 70-75 KTS THROUGH THE
SOUTHEASTERN QUADRANT.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 63 KTS AT 281800Z
   CIMSS ADT: 45 KTS AT 281830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 01W IS EXPECTED TO CONTINUE TO TRACK
NORTHEASTWARD UNDER THE INFLUENCE OF THE WELL-ESTABLISHED STR
POSITIONED TO THE EAST THROUGH THE END OF THE 72 HOUR FORECAST
PERIOD. THE TYPHOON IS FORECAST TO REMAIN IN A MARGINALLY FAVORABLE
ENVIRONMENT WITH A CONTINUED INTENSITY OF 75 KTS THROUGHOUT THE
NEXT 12 HOURS AS FAVORABLE UPPER-LEVEL OUTFLOW AND WARM SEA SURFACE
TEMPERATURES (28-29 C), REMAIN CONDUCIVE FOR SUSTAINMENT IN THE 
NORTHERN PHILIPPINE SEA. AFTER TAU 18, THE SOUTHWARD EXTENSION OF THE 
LONGWAVE TROUGH IS FORECASTED TO CONTINUE EASTWARD, INCREASING VWS TO 
20-30 KTS, BEGINNING THE STAGES OF A STEADY WEAKENING TREND. AS TY 01W 
CONTINUES TO TRACK NORTHEASTWARD AFTER TAU 24, COOLER SEA SURFACE 
TEMPERATURES WILL FURTHER WEAKEN THE SYSTEM NORTH OF LATITUDE 26N. BY 
TAU 36, THE SYSTEM WILL BEGIN TO UNDERGO EXTRATROPICAL TRANSITION AS 
COOL AND DRY AIR BEGINS WRAPPING INTO THE VORTEX FROM THE NORTHWEST 
AND CONTINUES UNTIL THE END OF THE FORECAST PERIOD. THROUGH 
EXTRATROPICAL TRANSITION, VWS WILL INCREASE ABOVE 30 KTS, DECOUPLING 
THE MID AND UPPER-LEVELS OF TY 01W.

MODEL DISCUSSION: THE DETERMINISTIC AND ENSEMBLE MODELS REMAIN IN
VERY STRONG AGREEMENT THAT TY 01W WILL TRACK NORTHEASTWARD THROUGH
TAU 72 ALONG THE NORTHWEST QUADRANT OF THE SUBTROPICAL RIDGE. GFS
AND ECMWF ENSEMBLE MEMBERS SHOW MINIMAL SOLUTIONS ALONG THE EXTREME
EASTERN EDGE OF MAINLAND JAPAN, WHILE THE JTWC CONSENSUS (CONW) 
REMAINS ALIGNED THAT THE SYSTEM WILL REMAIN TO THE EAST THROUGH THE
FORECASTED EXTRATROPICAL TRANSITION BETWEEN TAU 36 AND TAU 72. THE
TAU 24 AND TAU 48 CROSS-TRACK SPREADS REMAIN IN TIGHT AGREEMENT
BETWEEN 47NM AND 83NM RESPECTIVELY. INTENSITY GUIDANCE REMAINS IN
GOOD AGREEMENT THAT A STEADY INTENSITY WILL CONTINUE OVER THE NEXT
12 HOURS, WITH ITS STEADY WEAKENING TREND THEREAFTER. AFTER TAU
12, GFS, ECMWF, HAFS-A, AND COAMPS-TC SHOW A WEAKENING TREND
THROUGH THE REMAINDER OF THE 72 HOUR FORECAST PERIOD.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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