WDPN32 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (SAOLA) WARNING NR 034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.8N 116.3E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 121 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:
AS REVEALED IN ANIMATED RADAR IMAGERY, TYPHOON (TY) 09W HAS
COMMENCED ANOTHER EYEWALL REPLACEMENT CYCLE (ERC) WITH A SMALL
INNER EYEWALL SURROUNDED BY A MOAT AND DEVELOPING OUTER EYEWALL.
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 17 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. THE INITIAL INTENSITY OF 120 KTS
IS ASSESSED WITH HIGH CONFIDENCE BASED ON DVORAK INTENSITY ESTIMATES 
RANGING FROM 6.0 TO 6.5, A 010000Z AIDT ESTIMATE OF 121 KNOTS, AND AN 
RCM-3 SAR VMAX OF 116 KNOTS. THE WIND RADII HAVE BEEN EXPANDED BASED 
ON THE RCM-3 SAR PASS WITH HIGH CONFIDENCE.

INITIAL WIND RADII BASIS: SAR DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 127 KTS AT 312330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TY 09W IS FORECAST TO TRACK WEST-NORTHWESTWARD
TO WESTWARD 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. THE ONGOING ERC WILL 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: WITH THE EXCEPTION OF THE UKMET ENSEMBLE MEAN
(UEMN), WHICH LOOPS THE SYSTEM SOUTH OF HONG KONG, NUMERICAL MODEL
GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 36 WITH A 45 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 311200Z ECMWF ENSEMBLE ALSO INDICATES SIGNIFICANT UNCERTAINTY IN 
THE TIMING OF THE EASTWARD TURN, POSSIBLY AS FAR WEST AS THE GULF OF 
TONKIN. THE 311800Z GFS ENSEMBLE SHOWS THE BULK OF THE SOLUTIONS 
TURNING THE SYSTEM OVER OR TO THE 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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