WDPN32 PGTW 312100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (SAOLA) WARNING NR 033//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.6N 116.8E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 151 NM EAST-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 09W HAS COMPLETED AN EYEWALL REPLACEMENT CYCLE (ERC)
WITH AN ASSOCIATED 15 KNOT DECREASE IN INTENSITY OVER THE PAST 12
HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND RADAR
IMAGERY DEPICT A 20 NM ROUND EYE WITH TIGHTLY CURVED SPIRAL BANDING, 
WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. OVERALL, 
ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE AS THE SYSTEM SLOWLY 
APPROACHES HONG KONG WITH RADIAL OUTFLOW AND AN ENHANCED POLEWARD 
OUTFLOW CHANNEL INTO THE WESTERLIES TO THE NORTH. DVORAK CURRENT 
INTENSITY ESTIMATES HAVE DECREASED AND NOW RANGE FROM 6.0 TO 6.5 (115 
TO 127 KNOTS) SUPPORTING THE INITIAL INTENSITY WITH MEDIUM 
CONFIDENCE. THE CIMSS M-PERC PRODUCT INDICATES ANOTHER ERC IS 
IMMINENT WITH THE FULL MODEL DATA INDICATING A 75 PERCENT PROBABILITY 
AND ANIMATED RADAR IMAGERY SHOWING A MOAT FEATURE AND DEVELOPING 
OUTER EYEWALL.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WEAK EXTENSION OF THE SUBTROPICAL RIDGE
TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 112 KTS AT 311730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: STY 09W IS FORECAST TO TRACK WEST-NORTHWESTWARD 
ALONG THE SOUTHERN PERIPHERY OF THE STR THROUGH TAU 24. AFTER TAU 24, 
THE SYSTEM WILL TRANSITION TO THE STEERING INFLUENCE OF A BROAD 
WESTERN STR, WHICH WILL DRIVE THE SYSTEM WEST-SOUTHWESTWARD TO 
SOUTHWARD THROUGH TAU 72. TY 09W WILL WEAKEN STEADILY DUE TO 
FRICTIONAL EFFECTS AND DRY AIR ENTRAINMENT AS IT SKIRTS THE SOUTHEAST 
COAST OF CHINA. A POSSIBLE ERC MAY ALSO CONTRIBUTE TO FURTHER 
WEAKENING OVER THE NEXT 24 HOURS AS THE SYSTEM APPROACHES HONG KONG. 
AFTER TAU 72, TY 09W WILL TURN SHARPLY EASTWARD AS THE STEERING 
INFLUENCE TRANSITIONS TO A LOW-LEVEL NEAR-EQUATORIAL RIDGE TO THE 
SOUTH AND ASSOCIATED VIGOROUS SOUTHWESTERLIES.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 36 WITH A 50 NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU
36. AFTER TAU 36, GUIDANCE DIVERGES WITH SIGNIFICANT DIFFERENCES IN
THE DEGREE AND TIMING OF THE EASTWARD TURN. DUE TO THE LARGE DEGREE
OF UNCERTAINTY, THERE IS MEDIUM OVERALL CONFIDENCE IN THE JTWC
TRACK FORECAST THROUGH TAU 120. THE 310600Z ECMWF ENSEMBLE ALSO
INDICATES SIGNIFICANT UNCERTAINTY IN THE TIMING OF THE EASTWARD
TURN, POSSIBLY AS FAR WEST AS THE GULF OF TONKIN. THE 311200Z GFS
ENSEMBLE SHOWS THE BULK OF THE SOLUTIONS TURNING THE SYSTEM EAST OF
HAINAN ISLAND. RELIABLE INTENSITY GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 120 LENDING MEDIUM CONFIDENCE TO THE JTWC INTENSITY
FORECAST.

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