WDXS32 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (SEAN)       
WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.1S 109.2E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 291 NM WEST-SOUTHWEST OF LEARMONTH,
                         AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 37 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED WATER VAPOR RGB IMAGERY INDICATES AN EXTENSIVE REGION OF 
VERY DRY AIR ENCROACHING ON THE WESTERN SEMICIRCLE OF THE SYSTEM, 
ERODING DEEP CONVECTION AND SHRINKING THE CENTRAL CONVECTION. 
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SMALL 
CONVECTIVE CORE PERSISTING OVER THE LOW-LEVEL CIRCULATION CENTER 
(LLCC), WITH TIGHTLY-CURVED BANDING WRAPPING INTO A DEFINED LLCC. A 
202253Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE IMAGE REVEALS LIMITED 
DEEP CONVECTIVE BANDING OVER THE EASTERN QUADRANT WRAPPING INTO A 
DEFINED LLCC, WITH THE BULK OF THE DEEP CONVECTION CONFINED TO THE 
EASTERN SEMICIRCLE. ROBUST RADIAL OUTFLOW HAS PERSISTED, MAINTAINING 
THE RAPIDLY DWINDLING CORE CONVECTION. THE INITIAL POSITION IS PLACED 
WITH MEDIUM CONFIDENCE BASED ON THE EIR IMAGERY AND THE SSMIS IMAGE. 
THE INITIAL INTENSITY OF 95 KTS IS ASSESSED WITH MEDIUM CONFIDENCE 
BASED ON THE DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM 5.0-5.5 
(90-102 KNOTS). THE CIMSS OBJECTIVE ESTIMATES RANGE FROM 65 TO 96 
KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
ENTRENCHED OVER WESTERN AUSTRALIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T5.0 - 90 KTS
   DEMS: T5.5 - 102 KTS
   CIMSS SATCON: 96 KTS AT 202000Z
   CIMSS ADT: 90 KTS AT 210000Z
   CIMSS AIDT: 80 KTS AT 210000Z
   CIMSS D-MINT: 78 KTS AT 212255Z
   CIMSS D-PRINT: 65 KTS AT 210000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: UPPER-LEVEL DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 10S WILL TRACK SOUTHWESTWARD THROUGH TAU 12
THEN TURN SOUTHWARD THROUGH TAU 36 AS IT TRACKS ALONG THE WESTERN
PERIPHERY OF THE STR. SST VALUES WILL COOL STEADILY FROM ABOUT 24C
TO 22C BY TAU 36. STRONG VERTICAL WIND SHEAR (VWS) AND DRY AIR
ENTRAINMENT WILL FURTHER DEGRADE ENVIRONMENTAL CONDITIONS AFTER TAU
24 SUPPORTING A RAPID WEAKENING TREND. AFTER TAU 36, THE SYSTEM
WILL RECURVE SOUTH-SOUTHEASTWARD AROUND THE SOUTHERN PERIPHERY OF
THE STR, ENCOUNTERING STRONG WESTERLIES AND VWS ASSOCIATED WITH THE
SUBTROPICAL JET. TC 10S WILL ENTER A VERY DRY ENVIRONMENT AND TRACK
OVER COLD SST VALUES NEAR 20C, WHICH WILL LEAD TO DISSIPATION BY
TAU 72.    

MODEL DISCUSSION: DETERMINISTIC GUIDANCE IS NOW IN TIGHT AGREEMENT
THROUGH TAU 48, WITH A 55NM CROSS-TRACK SPREAD AT TAU 48, DIVERGING
TO ABOUT 105NM BY TAU 72. PROBABILISTIC GUIDANCE IS ALSO IN TIGHT
AGREEMENT THROUGH TAU 48, WITH INCREASING SPREAD AFTER TAU 48.
OVERALL TRACK CONFIDENCE IS ASSESSED AT HIGH. RELIABLE INTENSITY
GUIDANCE IS IN GOOD AGREEMENT AND SUPPORTS THE RAPID WEAKENING
FORECAST WITH MEDIUM CONFIDENCE. 

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