WDPN32 PGTW 310900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 09W (SAOLA) WARNING NR 
031//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.2N 117.8E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 211 NM EAST-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM HAS
MAINTAINED A HIGHLY SYMMETRICAL AND DENSE CENTRAL CONVECTION WITH A
SHARPLY OUTLINED 20-NM EYE. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE EYE. THE INITIAL INTENSITY OF 135KTS
IS ALSO PLACED WITH HIGH CONFIDENCE BASED ON AN OVERALL ASSESSMENT
OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SUSTAINED
INTENSE 6-HR CONVECTIVE AND WRAP MSI SIGNATURE. ANALYSIS INDICATES
A HIGHLY FAVORABLE ENVIRONMENT WITH VERY WARM SST IN THE SOUTH
CHINA SEA, LOW VWS, AND STRONG RADIAL OUTFLOW. ADDITIONALLY, STY
09W IS SLOWLY UNDERGOING AN EYEWALL REPLACEMENT CYCLE (ERC) BUT HAS
NOT WEAKENED THE SYSTEM AS OF YET.

INITIAL WIND RADII BASIS: PERSISTENCE.

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T7.0 - 140 KTS 
   RCTP: T7.0 - 140 KTS 
   CIMSS ADT: 134 KTS AT 310530Z
   CIMSS D-PRINT: 121 KTS AT 310630Z
   CIMSS D-MINT: 131 KTS AT 302140Z

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

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: STY SAOLA WILL TRACK ON A FLATTER
WEST-NORTHWESTWARD TO WESTWARD TRAJECTORY AS THE STEERING STR
BUILDS. AFTER TAU 36, A SECONDARY STR TO THE WEST WILL ASSUME
STEERING AND DRIVE THE CYCLONE SOUTHWESTWARD. THE ERC IS EXPECTED
TO SLOWLY WEAKEN THE CORE OF THE STY 10W; THIS, IN ADDITION TO LAND
INTERACTION WITH EASTERN SEABOARD OF CHINA WILL LEAD TO A GRADUAL
WEAKENING TO 70KTS BY TAU 48 AFTER IT BRUSHES HONG KONG. AFTER TAU
48, A MORE RAPID EROSION IS EXPECTED AS COOL DRY AIR FROM THE
CHINESE INTERIOR INTRUDES INTO THE LOW LEVEL CIRCULATION, KNOCKING
DOWN THE INTENSITY TO 40KTS BY TAU 72. AFTERWARD, A SCALED DOWN AND
WEAKER 35-KT 09W WILL LOOP AND DRIFT NORTHEASTWARD WITH THE MONSOON
FLOW, ENHANCED BY A SHALLOW NEAR-EQUATORIAL RIDGE TO THE SOUTH.   

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. A NOTABLE OUTLIER IS UKMET THAT CONTINUES 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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