WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (KOINU)       
WARNING NR 039//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.7N 113.2E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 66 NM WEST-SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 14W IS SKIRTING THE SOUTHEAST COAST OF CHINA,
WITH FRICTIONAL EFFECTS AND SOME DRY AIR ENTRAINMENT CONTRIBUTING
TO A RAPID WEAKENING TREND. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS RAPIDLY ERODING CORE CONVECTION WITH
FRAGMENTED CONVECTIVE BANDING OVER THE WESTERN AND NORTHERN
QUADRANTS. THE DEFINED CENTER EVIDENT IN RADAR IMAGERY EARLIER,
WHICH SUPPORTS THE INITIAL POSITION, HAS SUBSEQUENTLY DISSIPATED.
SURFACE OBSERVATIONS ARE LIMITED BUT THE LATEST REPORTS FROM
SHANGCHUAN DAO, APPROXIMATELY 21 NM WEST OF THE CENTER, ARE
UNIMPRESSIVE AT 20 TO 25 KNOTS (10-MINUTE AVERAGE). THE INITIAL
INTENSITY IS ASSESSED AT 60 KNOTS BASED ON AN AVERAGE OF THE DVORAK
CURRENT INTENSITY ESTIMATES RANGING FROM 55 TO 65 KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK, COMPETING STEERING ENVIRONMENT
WITH A DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST
AND A WEAK STR OVER SOUTHEAST ASIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS ADT: 39 KTS AT 082330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: INTERACTION WITH LAND

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: THE LOW- TO MID-LEVEL STR IS FORECAST TO BUILD
TO THE NORTH OF THE SYSTEM AND, CONSEQUENTLY, TS 14W IS FORECAST TO
ACCELERATE SOUTHWESTWARD TOWARD HAINAN ISLAND OVER THE NEXT 2 DAYS
WITH STEADY WEAKENING. RAPID WEAKENING WILL OCCUR AS THE SYSTEM
CROSSES HAINAN ISLAND AND DISSIPATION IS EXPECTED TO OCCUR BY TAU
96 OR EARLIER AS THE SYSTEM TRACKS INTO VIETNAM AND LAOS.

MODEL DISCUSSION: THE DETERMINISTIC MODEL TRACKERS ARE IN FAIR
AGREEMENT THROUGH THE FORECAST PERIOD. THE 081800Z EPS AND GEFS
ENSEMBLES SUPPORT THE JTWC FORECAST PHILOSOPHY WITH ALL SOLUTIONS
INDICATING A SOUTHWESTWARD TRACK WITH RAPID WEAKENING.

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