WDPN31 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.2N 113.3E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 344 NM NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 03 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 A COMPACT AND SYMMETRICAL COLD CENTRAL
COVER; HOWEVER, IT IS NOW SHOWING SIGNS OF WEAKENING AS INDICATED
BY WARMING IN THE OVERSHOOTING CLOUD TOPS AND A DEFINED EYE THAT
HAS SINCE SHRUNK TO 9NM AND HAS BECOME RAGGED AND PARTIALLY CLOUD-
FILLED. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
THE DEFINED EYE. THE INITIAL INTENSITY IS ALSO ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE OVERALL ASSESSMENT OF CLOSELY-CLUSTERED AGENCY 
AND AUTOMATED DVORAK FIXES AND REFLECTS THE SLIGHT DEGRADATION IN THE 
6-HR EIR-BD LOOP. ANALYSIS INDICATES THE ENVIRONMENT REMAINS, FOR NOW, 
FAVORABLE WITH LOW VWS, AND MODERATE POLEWARD OUTFLOW, OFFSET ONLY BY 
COOLING ALONG-TRACK SST.

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: NEUTRAL IN THE COL BETWEEN THE DEEP-
LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST AND A SECONDARY STR 
TO THE WEST ANCHORED OVER THE INDOCHINA PENINSULA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T6.0 - 115 KTS
   CIMSS SATCON: 106 KTS AT 091336Z
   CIMSS ADT: 107 KTS AT 091730Z
   CIMSS DPRNT: 102 KTS AT 091730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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 SLOWLY EXIT THE COL AREA
AND BEGIN TO TRACK SOUTHWESTWARD TOWARD SOUTHERN VIETNAM AS THE
SECONDARY STR TO THE WEST ASSUMES STEERING. THE ENVIRONMENT WILL 
SLOWLY BECOME UNFAVORABLE WITH THE INTRUSION OF CONTINENTAL DRY AIR 
AND DIMINISHING POLEWARD OUTFLOW IN ADDITION TO THE COOLER SST, 
GRADUALLY WEAKENING THE SYSTEM TO 70KTS BY TAU 24. AFTERWARD, THE 
ADDITION OF INCREASING VWS AND LAND INTERACTION WILL RAPIDLY ERODE THE 
SYSTEM TO DISSIPATION BY TAU 72, POSSIBLY SOONER, AS IT MAKES LANDFALL 
OVER CENTRAL VIETNAM, JUST SOUTH OF DA NANG. 
 
MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT, GRADUALLY 
SPREADING OUT TO 116NM BY TAU 72; HOWEVER, DUE TO THE UNCERTAINTY IN 
THE STORM MOTION AS THE CYCLONE EXITS THE COL AREA, THERE IS ONLY 
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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