WDPN31 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.8N 113.0E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 221 NM SOUTH-SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 49 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS STEADY 
WEAKENING, WITH A DETERIORATING, MORE ASYMMETRIC CENTRAL DENSE 
OVERCAST DUE PRIMARILY TO COOLER SST NEAR 26C AND INCREASING VERTICAL 
WIND SHEAR. A 100617Z AMSR2 COLOR 37GHZ MICROWAVE IMAGE SHOWS A 
PARTIAL EYEWALL OVER THE NORTHERN QUADRANT AND A WELL-DEFINED LOW-
LEVEL CIRCULATION CENTER, WHICH SUPPORTS THE INITIAL POSITION WITH 
HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 90 KNOTS BASED 
ON THE AGENCY DVORAK ESTIMATES FROM PGTW AND RJTD AND THE CIMSS ADT 
ESTIMATE. 

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   CIMSS SATCON: 83 KTS AT 100332Z
   CIMSS ADT: 90 KTS AT 100530Z
   CIMSS AIDT: 85 KTS AT 100530Z
   CIMSS D-PRINT: 78 KTS AT 100700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 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 90NM AT TAU 36 AND 120NM AT
TAU 48. THE 091800Z ECMWF ENSEMBLE (EPS) AND 100000Z 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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