WDPN31 PGTW 290300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 01W (EWINIAR) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.3N 130.8E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 209 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A DISTINCT
LOW-LEVEL CIRCULATION CENTER (LLCC) WRAPPING TIGHTLY BENEATH THE
WESTERN EDGE OF THE SYSTEM'S CONVECTIVE CURVED BANDING. THE
ASYMMETRIC CONVECTION HAS CONTINUED TO WARM OVER THE LAST FEW
HOURS, SIGNIFYING THE BEGINNING STAGES OF THE EXPECTED WEAKENING
TREND FOR TYPHOON (TY) 01W. MODERATE VERTICAL WIND SHEAR (VWS) OF
20-25 KTS CONTINUES TO REMAIN EVIDENT THROUGHOUT THE REMAINING
CIRRUS SHIELD, WITH OBSERVABLE STRIATIONS THROUGHOUT THE EASTERN
PERIPHERY OF THE SYSTEM ON ANIMATED WATER VAPOR IMAGERY. STRONG
DUAL-CHANNEL UPPER-LEVEL OUTFLOW HAS PERSISTED THROUGH THE PREVIOUS
SIX HOURS, WITH A POWERFUL LONGWAVE TROUGH INDUCED POLEWARD
CHANNEL, AND THE CONTINUOUS SOUTHWARD CHANNEL OVER THE PHILIPPINE
SEA. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
EXTRAPOLATION FROM THE 282121Z RCM-3 SAR IMAGE AND THE RJTD RADAR
FIX FROM MINAMI-DAITOJIMA ISLAND. THE INITIAL INTENSITY OF 70 KTS
WAS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SUBJECTIVE AGENCY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SAR DATA.

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T5.0 - 90 KTS
   CIMSS SATCON: 63 KTS AT 1930Z
   CIMSS ADT: 43 KTS AT 280030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-28 CELSIUS
   OUTFLOW: STRONG 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 FORECASTED TO CONTINUE TO TRACK
NORTHEASTWARD AROUND THE WESTERN AND NORTHWESTERN PERIPHERY OF THE
DEEP-LAYER SUBTROPICAL STEERING RIDGE THROUGH TAU 72 OF THE
FORECAST. THE TYPHOON IS EXPECTED TO BEGIN ENTERING A GENERALLY
NON-CONDUCIVE ENVIRONMENT FOR FURTHER INTENSIFICATION AS MODERATE
TO STRONG VWS (20-30 KTS) WILL INCREASE THROUGHOUT THE NEXT 12
HOURS. ALTHOUGH SEA SURFACE TEMPERATURES REMAIN WARM (26-28 C) AND
UPPER-LEVEL OUTFLOW IS SUPPORTIVE OF FURTHER DEEPENING IN THE
PHILIPPINE SEA, THE INFLUENCE FROM THE MID-LATITUDE WESTERLIES WITH
STRONG VWS WILL CAUSE CONTINUED WEAKENING UNTIL EXTRATROPICAL
TRANSITION TO AN ASYMMETRIC COLD-CORE BAROCLINIC LOW. AS TY 01W
CONTINUES TO TRACK NORTHEASTWARD BETWEEN TAU 12 AND TAU 18, COOL
SEA SURFACE TEMPERATURES (25-27 C) WILL AID IN THE STEADY WEAKENING
OF THE SYSTEM. INTO TAU 36, THE TYPHOON WILL BEGIN UNDERGOING
EXTRATROPICAL TRANSITION AS DRY AIR ENTRAINS INTO THE CORE
STRUCTURE, AND COLD-AIR ADVECTION AMPLIFIES FROM THE NORTHWEST AND
LASTS THROUGH THE REMAINDER OF THE 72 HOUR FORECAST.  

MODEL DISCUSSION: THE DETERMINISTIC AND ENSEMBLE MODELS ARE IN VERY
STRONG AGREEMENT THAT TY 01W WILL TRACK TO THE NORTHEAST THROUGH
TAU 72 ALONG THE NORTHWEST PERIPHERY OF THE SUBTROPICAL STEERING
RIDGE. GFS AND ECMWF ENSEMBLE MEMBERS NO LONGER EXHIBIT SOLUTIONS
WITHIN MAINLAND JAPAN, WHILE THE JTWC CONSENSUS (CONW) IS IN
COMPLETE AGREEMENT THAT TY 01W WILL REMAIN TO THE EAST THROUGHOUT
THE REMAINDER OF THE 72 HOUR FORECAST PERIOD. CROSS-TRACK SPREADS
THROUGHOUT TAU 72 REMAIN BELOW 73NM. INTENSITY GUIDANCE REMAINS IN
GOOD AGREEMENT THAT A STEADY WEAKENING TREND IS FORECASTED THROUGH
EXTRATROPICAL TRANSITION, HOWEVER, SLIGHT REINTENSIFICATION IS
INDICATED ON GFS, ECMWF, HAFS-A, AND COAMPS-TC AFTER TAU 48, AND AS
THE EXPECTED ASYMMETRIC BAROCLINIC EXTRATROPICAL LOW DEEPENS BETWEEN 
TAU 48 AND TAU 72.  

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