WDPN31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (IN-FA) WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.5N 125.9E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 208 NM SOUTH-SOUTHWEST OF KADENA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND RADAR IMAGERY 
INDICATE A GENERAL WEAKENING TREND WITH SPIRAL BANDING OVER
THE SOUTHERN SEMICIRCLE AND A LARGE EYE. A 220729Z SSMI 37GHZ
MICROWAVE IMAGE DEPICTS A RAGGED MICROWAVE EYE FEATURE, WHICH
SUPPORTS THE INITIAL POSITION WITH MEDIUM CONFIDENCE. THE INITIAL
INTENSITY OF 85 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A
BLEND OF THE PGTW AND KNES DVORAK DATA-T ESTIMATES OF 4.5 WITH 
CURRENT INTENSITY ESTIMATES OF 5.0. UPPER-LEVEL ANALYSIS INDICATES 
FAVORABLE CONDITIONS WITH LOW VERTICAL WIND SHEAR AND MODERATE 
RADIAL OUTFLOW ALTHOUGH A SMALL UPPER-LEVEL CYCLONE REMAINS 
POSITIONED OVER THE SYSTEM'S CENTER DIVERGING AWAY FROM THE CENTER.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 97 KTS AT 220540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: EXTENDED FORECAST TRACK SPEEDS HAVE
BEEN DECREASED DUE TO MAJOR SHORTWAVE TROUGH DIGGING OVER EASTERN
CHINA AND THE WEST SEA AFTER TAU 72.

FORECAST DISCUSSION: TY 09W IS TRACKING SLOWLY ALONG THE SOUTHERN
PERIPHERY OF THE STR DUE TO THE PRESENCE OF A COMPETING
NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTH. THE BULK OF THE MODELS
INDICATE THE STR SHOULD RE-ORIENT, AS A MIDLATITUDE TROUGH
PROPAGATES OVER NORTHEAST ASIA, AND ACCELERATE THE SYSTEM
NORTH-NORTHWESTWARD THROUGH TAU 72 TOWARD THE SHANGHAI REGION.
SLIGHT INTENSIFICATION TO 90 KNOTS IS EXPECTED IN THE SHORT-TERM
THEN GRADUAL WEAKENING AS TY 09W APPROACHES THE CHINA COAST. AFTER
TAU 72, THE SYSTEM WILL SLOW AS A MAJOR SHORTWAVE TROUGH DIGS OVER
EASTERN CHINA AND TRACK OVERLAND LEADING TO RAPID WEAKENING DUE
PRIMARILY TO WEAK POLEWARD OUTFLOW AND EVENTUAL DISSIPATION DUE TO
INTERACTION WITH LAND.         

MODEL DISCUSSION: THERE IS A DISTINCT SPLIT IN THE NUMERICAL MODELS
WITH THE BULK OF THE GUIDANCE SUPPORTING THE JTWC FORECAST TRACK
OVERLAND. THE GFS AND GEFS TRACKERS, HOWEVER, DEPICT A
QUASI-STATIONARY MOTION THEN A POLEWARD TRACK AFTER TAU 120 TOWARD
THE KOREAN PENINSULA. THE GFS TRACK SCENARIO IS BASED ON
SIGNIFICANT WEAKENING OF THE STR VERSUS THE OTHER MODELS WHICH
MAINTAIN A WEAK STEERING RIDGE SUFFICIENT TO TURN THE SYSTEM WEST
OVER CHINA. THE CURRENT FORECAST SCENARIO IS MAINTAINED WITH LOW
CONFIDENCE BUT THE GFS SOLUTION WILL BE CLOSELY MONITORED AND
EVALUATED OVER THE NEXT COUPLE DAYS. THERE IS MEDIUM CONFIDENCE IN
THE JTWC INTENSITY FORECAST WITH CLOSE AGREEMENT IN THE INTENSITY
GUIDANCE.      

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