WDPN31 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (KOINU) WARNING NR 037//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.6N 114.1E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 42 NM SOUTH OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM
HAS ONCE AGAIN BECOME QUASI-STATIONARY AS IT MAINTAINED A COMPACT
CENTRAL DENSE OVERCAST. HOWEVER, THE CONVECTIVE STRUCTURE CONTINUED
TO WEAKEN AS EVIDENCED BY THE CLOSED EYE AND WARMING CLOUD TOPS.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
DEFINED LOW LEVEL CIRCULATI0N FEATURES IN A COMPOSITE RADAR LOOP AND 
IN THE 081018Z SSMIS MICROWAVE IMAGE. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE HIGH END OF AGENCY AND
AUTOMATED DVORAK ESTIMATES AND REFLECTS THE 6-HR DEGRADED
CONVECTIVE STRUCTURE.

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE WEST AND
A DEEP LAYER STR TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS ADT: 51 KTS AT 081130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 KOINU WILL SLOWLY DRIFT SOUTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR TO THE WEST. THE MARGINALLY
UNFAVORABLE ENVIRONMENT BECOMING MORE UNFAVORABLE, EXACERBATED BY  
DRY AIR INTRUSION FROM MAINLAND CHINA PLUS LANDFALL INTO HAINAN 
AROUND TAU 42, THEN FINAL LANDFALL INTO CENTRAL VIETNAM AROUND TAU 
72, WILL ERODE THE SYSTEM TO DISSIPATION BY TAU 96 AFTER IT CROSSES 
INTO LAOS. THERE IS A DISTINCT POSSIBILITY THAT TY 14W WILL DISSIPATE
MUCH SOONER. 


MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT
WITH A SPREAD TO 186NM BY TAU 72, THEN MORE ERRATIC BY TAU 96 AS
THE MODELS LOSE THE VORTEX, LENDING MEDIUM CONFIDENCE TO THE JTWC
TRACK AND INTENSITY FORECAST UP TO TAU 72 THEN LOW CONFIDENCE
AFTERWARD.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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