WDPN32 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (SAOLA) WARNING NR 035//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0N 115.4E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 69 NM EAST-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 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;
HOWEVER, THE OUTER EYEWALL REMAINS FRAGMENTED AS IT STRUGGLES TO
ENVELOPE AND REPLACE THE INNER EYEWALL WITH ITS SHARPLY OUTLINED
19-NM EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE EYE. THE INITIAL INTENSITY OF 120KTS IS ALSO PLACED
WITH HIGH CONFIDENCE BASED ON AN OVERALL ASSESSMENT OF AGENCY AND
AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SLIGHT 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. ADDITIONALLY, TY
09W IS UNDERGOING AN EYEWALL REPLACEMENT CYCLE (ERC) WHICH HAS
SLIGHTLY WEAKENED THE SYSTEM.

INITIAL WIND RADII BASIS: SAR DATA.

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
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 112 KTS AT 010509Z
   CIMSS ADT: 127 KTS AT 010530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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 SAOLA WILL TRACK MORE WESTWARD UNDER THE
STEERING INFLUENCE OF THE STR TO THE NORTH, PASSING JUST 17NM SOUTH
OF HONG KONG ON 010500Z. AFTER TAU 24, 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 TO THE ERC WILL RAPIDLY WEAKEN STY 10W DOWN TO
50KTS BY TAU 48. 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 25KTS BY TAU 120. 
CONCURRENTLY DURING THIS EXTENDED PORTION OF THE FORECAST, 09W WILL 
LOOP COUNTERCLOCKWISE OVER HAINAN TRACK NORTHEASTWARD BACK INTO THE 
SOUTH CHINA SEA, STEERED BY A SHALLOW NEAR-EQUATORIAL RIDGE TO THE 
SOUTH. 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 NVGM 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: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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