WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.8N 115.0E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 215 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE
SYSTEM REMAINS VERY INTENSE WITH THE COMPACT COLD CENTRAL COVER, LADEN
WITH OVERSHOOTING CLOUD TOPS, MAINTAINING A DEFINED EYE THAT HAS SINCE
SHRUNK TO 13NM AND HAS BECOME PARTIALLY CLOUD-FILLED. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE DEFINED EYE IN
A LOW VWS ENVIRONMENT. THE INITIAL INTENSITY IS ALSO ASSESSED WITH
HIGH CONFIDENCE BASED ON EQUALLY ESTIMATED AND CLOSELY-CLUSTERED 
DVORAK FIXES FROM THREE REPORTING AGENCIES AND REFLECTS THE SUSTAINED 
6-HR EIR-BD CONVECTIVE SIGNATURE. ANALYSIS INDICATES A FAVORABLE
ENVIRONMENT WITH LOW VWS, WARM SST, AND STRONG POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE NORTH EXTENDING FROM SOUTHERN CHINA THROUGH TAIWAN. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   CIMSS SATCON: 104 KTS AT 082229Z
   CIMSS ADT: 117 KTS AT 082330Z
   CIMSS DPRNT: 100 KTS AT 082330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 05-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TYPHOON YINXING WILL CONTINUE ON ITS CURRENT
WEST-NORTHWESTWARD TRACK UNDER THE STEERING STR. BY TAU 12, A
SECONDARY STR BUILDING IN FROM THE SOUTHWEST OVER THE INDOCHINA
PENINSULA WILL SLOW DOWN THE FORWARD MOTION OF THE CYCLONE THEN
ASSUME STEERING, DRIVING IT SOUTHWESTWARD TOWARD SOUTHERN VIETNAM
BY TAU 24. THE FAVORABLE ENVIRONMENT WILL SHORTLY BECOME UNFAVORABLE 
WITH THE ONSET OF DRY AIR INTRUSION AND COOLER SST, GRADUALLY 
WEAKENING THE SYSTEM TO 65KTS BY TAU 36. AFTER TAU 36, SIGNIFICANTLY 
INCREASING VWS (30+ KTS) AND DRY AIR INTRUSION WILL RAPIDLY ERODE THE 
SYSTEM TO DISSIPATION BY TAU 72, POSSIBLY SOONER, AS IT MAKES LANDFALL 
OVER CENTRAL VIETNAM.    


MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT,
GRADUALLY SPREADING OUT TO 42NM BY TAU 36 THEN TO 201NM BY TAU 72,
LENDING OVERALL MEDIUM CONFIDENCE TO THE JTWC TRACK AND INTENSITY
FORECASTS.  

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