WDPN32 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (SAOLA) WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 114.4E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 16 NM SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM
HAS MAINTAINED A HIGHLY SYMMETRICAL AND DENSE CENTRAL CONVECTION EVEN 
AS THE NORTHERN HALF HAS MADE LANDFALL INTO HONG KONG AND INLAND 
CHINA; AN EYEWALL REPLACEMENT CYCLE HAS FAILED TO TRANSPIRE AS THE 
OUTER EYEWALL HAS MOSTLY ERODED LEAVING THE INNER EYEWALL INTACT WITH 
ITS WELL-DEFINED BUT CONSTRICTING 8-NM PINHOLE EYE. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PINHOLE EYE.
THE INITIAL INTENSITY OF 115KTS IS ALSO PLACED WITH HIGH CONFIDENCE
BASED ON AN OVERALL ASSESSMENT OF AGENCY AND AUTOMATED DVORAK
ESTIMATES AND REFLECTS THE 6-HR CONVECTIVE DETERIORATION NEAR THE
CORE. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH VERY WARM SST
IN THE SOUTH CHINA SEA AND STRONG RADIAL OUTFLOW OFFSET BY MODERATE
TO STRONG VWS. 

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: DEEP LAYER SUBTROPICAL RIDGE (STR) TO
THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 115 KTS AT 011130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TY SAOLA WILL TRACK MORE WEST-SOUTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR TO THE NORTH, PASSING JUST
12NM SOUTH OF HONG KONG OVER THE NEXT TWO HOURS. AFTER TAU 12, A
SECONDARY STR TO THE WEST WILL ASSUME STEERING AND DRIVE THE CYCLONE 
SOUTHWESTWARD. INCREASING VWS AND LAND INTERACTION WITH THE EASTERN 
SEABOARD OF CHINA IN ADDITION COOL DRY AIR INTRUSION FROM THE CHINESE
INTERIOR WILL RAPIDLY WEAKEN STY 10W DOWN TO 45KTS BY TAU 48. AFTER
TAU 48, A MORE GRADUAL EROSION IS EXPECTED AS 09W WILL LOOP 
COUNTERCLOCKWISE OVER HAINAN THEN TRACK NORTHEASTWARD BACK INTO THE 
SOUTH CHINA SEA, STEERED BY A SHALLOW NEAR-EQUATORIAL RIDGE TO THE 
SOUTH, LEADING TO DISSIPATION OVER LAND BY TAU 120. THERE IS A 
DISTINCT POSSIBILITY THAT 09W WILL DISSIPATE BEFORE TAU 120.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL AGREEMENT WITH
THE LOOPING TRACK BUT DIVERGE SIGNIFICANTLY AFTER TAU 72, LENDING
MEDIUM CONFIDENCE TO THE JTWC TRACK FORECAST UP TO TAU 72, THEN LOW
CONFIDENCE AFTERWARD. NOTABLE OUTLIERS INCLUDE UKMET AND ECMWF THAT
CONTINUE TO DRIVE THE VORTEX SOUTHWESTWARD TOWARD VIETNAM AFTER TAU
72. ANOTHER NOTABLE OUTLIER IS GFS WITH A MUCH WIDER LOOP AFTER TAU
72. 


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