WDPN31 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.9N 126.5E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 346 NM EAST-NORTHEAST OF MANILA,
                         PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND ENHANCED INFRARED 
SATELLITE IMAGERY DEPICT A COMPACT, CONSOLIDATING SYSTEM, WITH A 
SYMMETRIC 100NM DIAMETER CENTRAL DENSE OVERCAST (CDO) FEATURE AND 
INTENSE CONVECTIVE BURSTS (-90C CLOUD TOPS). MSI ALSO SHOWS STRONG 
NORTHEASTERLY SURGE FLOW THROUGH THE LUZON AND TAIWAN STRAITS. THIS
LOW-LEVEL SURGE IS TRANSPORTING SIGNIFICANT DRY AIR INTO THE NORTHERN 
SOUTH CHINA SEA, WHICH WILL IMPACT THE SYSTEM IN THE EXTENDED 
FORECAST PERIOD. ENVIRONMENTAL CONDITIONS ARE CURRENTLY FAVORABLE, 
WITH LOW TO MODERATE VERTICAL WIND SHEAR (VWS) OFFSET BY STRONG 
POLEWARD OUTFLOW. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON THE MSI. THE INITIAL INTENSITY OF 80 KTS IS ASSESSED WITH 
HIGH CONFIDENCE BASED ON CONCURRENT AGENCY DVORAK ESTIMATES OF T4.5 
(77 KNOTS). THIS ESTIMATES IS ALSO SUPPORTED BY THE 050600Z CIMSS 
DPRINT AND AIDT ESTIMATES RANGING FROM 80-83 KNOTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTHEAST, WITH A BREAK TO THE NORTH ASSOCIATED
WITH A MIDLATITUDE MAJOR SHORTWAVE TROUGH DIGGING INTO THE EAST
CHINA SEA AND THE KOREAN PENINSULA.

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
   CIMSS SATCON: 74 KTS AT 050500Z
   CIMSS ADT: 74 KTS AT 050530Z
   CIMSS AIDT: 80 KTS AT 050600Z
   CIMSS DPRINT: 83 KTS AT 050600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR OVER THE WESTERN PERIPHERY

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 (TY) 24W IS FORECAST TO CONTINUE
TRACKING SLOWLY NORTHWESTWARD THROUGH TAU 12 ALONG THE SOUTHWEST 
PERIPHERY OF THE STR. AFTER TAU 12, THE AFOREMENTIONED SHORTWAVE 
TROUGH WILL PROPAGATE EASTWARD, WHICH WILL ALLOW THE STR TO REBUILD 
TO THE NORTH TURNING THE SYSTEM ONTO A WESTWARD TRAJECTORY THROUGH 
TAU 96. TY YINXING WILL SLOWLY INTENSIFY TO ABOUT 100 KNOTS BY TAU 24 
TO TAU 36, WITH GRADUAL WEAKENING AS THE SYSTEM SKIRTS BY NORTHERN
LUZON FROM TAU 36 TO TAU 72. THE PEAK INTENSITY WILL BE LIMITED
SOMEWHAT BY PERSISTENT LOW TO MODERATE VWS AND INTERACTION WITH
LAND. AFTER TAU 72, THE SYSTEM WILL TURN WEST-SOUTHWESTWARD AS IT
WEAKENS DUE TO SIGNIFICANT DRY AIR ENTRAINMENT, TRACKING WITHIN THE
LOW-LEVEL FLOW.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 72, WITH A 70NM TO 90NM CROSS-TRACK SPREAD FROM TAU 48
TO TAU 72. AFTER TAU 72, MODEL GUIDANCE DIVERGES WITH INCREASING
UNCERTAINTY IN THE FORECAST TRACK. BOTH THE 041800Z ECMWF ENSEMBLE
(EPS) AND THE 050000Z GFS ENSEMBLE (GEFS) SUPPORT THE JTWC TRACK
FORECAST AND SHOW ALL SOLUTIONS WEAKENING THE SYSTEM AFTER TAU 72
WITH A SHARP SOUTHWESTWARD TURN. RELIABLE INTENSITY GUIDANCE
SUPPORTS THE JTWC INTENSITY FORECAST, WITH HAFS-A AND HWRF PEAKING
THE SYSTEM FROM 95 TO 105 KNOTS AT TAU 12, AND RAPIDLY WEAKENING
THE SYSTEM AFTER TAU 96. 

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