WDPN31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.4N 125.7E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 319 NM EAST-NORTHEAST OF MANILA,
                         PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A COMPACT, 
SLOWLY CONSOLIDATING SYSTEM, WITH A 100NM DIAMETER CENTRAL DENSE 
OVERCAST (CDO) FEATURE AND DEVELOPING RAGGED EYE. A 050936Z RCM-1 SAR 
IMAGE REVEALS A 10NM DIAMETER CORE OF WEAK WINDS SURROUNDED BY A 
SYMMETRIC 50NM DIAMETER REGION OF TYPHOON STRENGTH WINDS. A LOW-LEVEL 
NORTHEASTERLY SURGE EVENT 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 MEDIUM 
CONFIDENCE BASED ON THE RCM-1 SAR IMAGE AND EIR IMAGERY. THE INITIAL 
INTENSITY OF 85 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN 
AVERAGE OF AGENCY DVORAK ESTIMATES RANGING FROM T4.5 TO T5.0. DESPITE 
THE CLEAR EVIDENCE OF A STRENGTHENING SYSTEM INCLUDING SAR DATA AND 
INCREASING DVORAK ESTIMATES, THE CIMSS ADT AND AIDT ESTIMATES HAVE 
DECREASED SHARPLY OVER THE PAST SIX HOURS, LIKELY DUE TO THE COMPACT 
SIZE OF THE SYSTEM. ALTHOUGH ASSESSED AS UNREALISTICALLY HIGH, THE 
MAXIMUM WIND VALUE IN THE RCM-1 SAR IMAGE IS 104 KNOTS.    

INITIAL WIND RADII BASIS: SAR 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: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 61 KTS AT 051200Z
   CIMSS AIDT: 70 KTS AT 051200Z
   CIMSS DPRINT: 71 KTS AT 051200Z

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: MEDIUM
   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: 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 60. THE PEAK INTENSITY WILL BE LIMITED 
SOMEWHAT BY PERSISTENT LOW TO MODERATE VWS, INTERACTION WITH LAND AND 
A POCKET OF MARGINAL SST NORTHEAST OF LUZON ASSOCIATED WITH UPWELLING 
FROM 23W. 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 AN 80NM 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 050600Z ECMWF ENSEMBLE
(EPS) AND THE 050600Z GFS ENSEMBLE (GEFS) SUPPORT THE JTWC TRACK
FORECAST AND SHOW THE OVERWHELMING MAJORITY OF SOLUTIONS WEAKENING 
THE SYSTEM AFTER TAU 72 WITH A SHARP SOUTHWESTWARD TURN. RELIABLE 
INTENSITY GUIDANCE SUPPORTS THE JTWC INTENSITY FORECAST, WITH HAFS-A 
PEAKING THE SYSTEM FROM 95 TO 100 KNOTS AT TAU 24, 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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