WDPN31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (KOINU) WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.5N 114.3E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 48 NM SOUTH OF HONG KONG
   MOVEMENT PAST 6 HOURS: WESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM HAS
MOVED SLOWLY WESTWARD FROM A QUASI-STATIONARY MODE AND MAINTAINED A
COMPACT CENTRAL DENSE OVERCAST AND A DIMPLE FEATURE FROM A RECENTLY
CLOUD-COVERED PINHOLE EYE. 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 THE DIMPLE FEATURE THAT IS CONCENTRIC WITH A DEFINED LOW
LEVEL CIRCULATI0N FEATURE IN A COMPOSITE RADAR LOOP. 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. 


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 SATCON: 56 KTS AT 080515Z
   CIMSS ADT: 51 KTS AT 080530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: LOW

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 WESTWARD THEN
SOUTHWESTWARD UNDER THE STEERING STR. 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 AFTER TAU 72, WILL
ERODE THE SYSTEM TO DISSIPATION BY TAU 120 AFTER IT CROSSES LAOS
INTO THAILAND. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT
WITH AN EVEN SPREAD TO 185NM 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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