WDPN31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (KOINU) WARNING NR 038//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.7N 113.7E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 45 NM SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON 14W IS TRACKING SLOWLY, PARALLEL TO THE SOUTHEAST COAST OF
CHINA, WITH FRICTIONAL EFFECTS AND SOME DRY AIR ENTRAINMENT
CONTRIBUTING TO A STEADY WEAKENING TREND. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY DEPICTS A RAPIDLY ERODING CENTRAL
DENSE OVERCAST WITH DEEP CONVECTION DECAYING OVER THE NORTHERN
SEMICIRCLE. ANIMATED RADAR IMAGERY STILL SHOWS AN EYE, WHICH
SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE, BUT THE
SOUTHERN PORTION OF THE EYEWALL IS BEGINNING TO WEAKEN AND OPEN UP.
DUE TO THE COMPACT STRUCTURE OF THE SYSTEM, COASTAL STATIONS
AVOIDED THE STRONGER WINDS. HOWEVER, WAGLAN ISLAND DID BRIEFLY
REPORT PEAK SUSTAINED WINDS OF 49 KNOTS (10-MINUTE AVERAGE) AT
080900Z. MORE RECENTLY, HONG KONG INTERNATIONAL AIRPORT REPORTED
PEAK SUSTAINED WINDS OF 31 KNOTS (10-MINUTE AVERAGE) AT 081600Z AND
MACAU, 30 NM NNW OF THE 081800Z CENTER, IS REPORTING 29 KNOT WINDS
(10-MINUTE AVERAGE) WITH AN SLP VALUE OF 1008.8MB. THE 181200Z
WARNING INTENSITY WAS REVISED FROM 75 KNOTS UP TO 85 KNOTS BASED ON
A 081025Z RCM-3 SAR MAXIMUM WIND VALUE OF 93 KNOTS. THE INITIAL
INTENSITY REFLECTS THE WEAKENING TREND AND IS ASSESSED AT 75 KNOTS
BASED ON THE DVORAK CURRENT INTENSITY ESTIMATE FROM RJTD.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   CIMSS ADT: 47 KTS AT 081730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: INTERACTION WITH LAND AND LOW- TO MID-LEVEL DRY
       AIR ENTRAINMENT ADVECTING OFF SOUTHEAST CHINA.

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: THE LOW- TO MID-LEVEL STR IS FORECAST TO BUILD
TO THE NORTH OF THE SYSTEM AND, CONSEQUENTLY, TY 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: WITH THE EXCEPTION OF NAVGEM, THE DETERMINISTIC
MODEL TRACKERS ARE IN FAIR AGREEMENT THROUGH THE FORECAST PERIOD.
THE 081200Z 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: MEDIUM
   INTENSITY 72-120 HR: HIGH//
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