WDPN31 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.7N 112.8E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 304 NM EAST-NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 43 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A RAPIDLY 
DETERIORATING CENTRAL DENSE OVERCAST DUE PRIMARILY TO COOLER SST NEAR 
26C, DRY AIR ENTRAINMENT AND INCREASING VERTICAL WIND SHEAR. A 
100839Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE IMAGE SHOWS A COMPACT 
EYEWALL SURROUNDING A MICROWAVE EYE FEATURE, WHICH SUPPORTS THE 
INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS 
ASSESSED AT 75 KNOTS BASED ON CONCURRENT AGENCY DVORAK CURRENT 
INTENSITY ESTIMATES OF 4.5 (77 KNOTS).

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT, WITH A 
SUBTROPICAL RIDGE (STR) TO THE EAST AND ANOTHER STR BUILDING TO THE
WEST AND NORTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS ADT: 84 KTS AT 101200Z
   CIMSS AIDT: 80 KTS AT 101200Z
   CIMSS D-PRINT: 76 KTS AT 101200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TYPHOON 24W IS FORECAST TO ACCELERATE 
SOUTHWESTWARD TO SOUTH-SOUTHWESTWARD AS THE STR REBUILDS TO THE
NORTHWEST. RAPID WEAKENING IS EXPECTED DUE PRIMARILY TO EXTENSIVE
DRY AIR ENTRAINMENT AND INCREASING VERTICAL WIND SHEAR. THE SYSTEM
WILL MAKE LANDFALL OVER VIETNAM JUST PRIOR TO TAU 48 AND WILL 
DISSIPATE BY TAU 48. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN FAIR
AGREEMENT WITH A CROSS-TRACK SPREAD OF 80NM AT TAU 36 AND 210NM AT
TAU 48. THE 100600Z ECMWF ENSEMBLE (EPS) AND 100600Z GFS ENSEMBLE
(GEFS) SUPPORT THE JTWC TRACK AND INTENSITY FORECAST WITH MEDIUM
CONFIDENCE. RELIABLE INTENSITY GUIDANCE SHOWS RAPID WEAKENING
THROUGH THE FORECAST PERIOD.   

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