WDPN31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (KOINU) WARNING NR 040//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.4N 112.8E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 95 NM SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM
CONTINUED TO RAPIDLY DETERIORATE WHILE MAINTAINING A COMPACT
CENTRAL DENSE OVERCAST WITH WARMING CONVECTIVE CLOUD TOPS.
SHALLOWER CONVECTIVE FEEDER BANDS HAVE ALSO BEEN UNRAVELING WITH
THE NORTHERN FLANK OVER LAND. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON
DEFINED LOW LEVEL CIRCULATI0N FEATURES 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: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS ADT: 34 KTS AT 090530Z
   CIMSS D-PRINT: 29 KTS AT 090600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR INTRUSION AND LAND INTERACTION.

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 DRIFT SOUTHWESTWARD UNDER
THE STEERING INFLUENCE OF THE STR TO THE WEST. THE UNFAVORABLE
ENVIRONMENT, EXACERBATED BY  
LANDFALL INTO HAINAN AROUND TAU 18, THEN FINAL LANDFALL INTO
CENTRAL VIETNAM BEFORE TAU 72, WILL ERODE THE SYSTEM TO DISSIPATION
AFTER LANDFALL. THERE IS A DISTINCT POSSIBILITY THAT TS 14W WILL
DISSIPATE
MUCH SOONER. 

MODEL DISCUSSION:  NUMERICAL MODELS ARE IN LOOSE AGREEMENT
WITH A WIDE AND ERRATIC SPREAD BY TAU 72 AS THE MODELS LOSE THE VORTEX, LENDING MEDIUM CONFIDENCE TO THE JTWC TRACK AND INTENSITY FORECAST.


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