WDXS32 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (SEAN) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.6S 111.7E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 140 NM WEST-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 52 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE
SYSTEM CONTINUED TO RAPIDLY INTENSIFY OVER THE LAST SIX HOURS AS 
EVIDENCED BY A MORE COMPACT COLD CENTRAL COVER THAT HAS DEVELOPED A 
SECONDARY EYEWALL AROUND ITS 10-NM PINHOLE EYE. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE PINHOLE EYE THAT LINED UP
PERFECTLY WITH THE DEFINED LOW LEVEL CIRCULATION IN THE COMPOSITE
RADAR LOOP FROM THE ABOM LEARMONTH RADAR SITE. THE INITIAL
INTENSITY OF 110KTS IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
HIGH END OF AGENCY DVORAK AND AUTOMATED INTENSITY ESTIMATES TO REFLECT 
THE SIGNIFICANT IMPROVEMENT IN THE 6-HR EIR CONVECTIVE SIGNATURE. 
ANALYSIS INDICATES A HIGHLY FAVORABLE ENVIRONMENT WITH STRONG RADIAL 
OUTFLOW AND LOW VWS SLIGHTLY OFFSET BY COOLING SST.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   DEMS: T5.0 - 90 KTS
   CIMSS ADT: 102 KTS AT 200600Z
   CIMSS AIDT: 98 KTS AT 200600Z
   CIMSS DPNT: 96 KTS AT 200530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG 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: TC SEAN WILL CONTINUE TO TRACK SOUTHWESTWARD
THEN SOUTHWARD AROUND THE NORTHWESTERN THEN WESTERN PERIPHERY OF
THE STEERING STR. THE FAVORABLE ENVIRONMENT WILL AT BEST MAINTAIN
THE CURRENT INTENSITY UP TO TAU 12. AFTERWARD, A GRADUAL EROSION
IS EXPECTED TO OCCUR WITH AN EYEWALL REPLACEMENT CYCLE EXPECTED TO
COMMENCE. THIS, PLUS THE CONTINUED COOLING SST, INCREASING VWS
AND, EVENTUALLY, DRY AIR INTRUSION WILL LEAD TO DISSIPATION BY TAU
96.

MODEL DISCUSSION: AVAILABLE NUMERICAL MODELS ARE IN TIGHT AGREEMENT
WITH THE MAIN PACK AT AN EVEN AND GRADUAL SPREAD TO A MERE 90NM BY
TAU 72, LENDING HIGH CONFIDENCE TO THIS PORTION OF THE JTWC TRACK
FORECAST. AFTERWARD, THE MODELS SPREAD OUT WIDER AND MORE UNEVENLY
TO OVER 500NM WITH UEMN THE EXTREME RIGHT-OF-TRACK OUTLIER, LENDING
ONLY MEDIUM CONFIDENCE TO THE EXTENDED PORTION OF THE TRACK
FORECAST THAT IS LAID TO THE LEFT OF CONSENSUS TO OFFSET UEMN.
THERE IS ONLY MEDIUM CONFIDENCE IN THE INTENSITY FORECAST DUE TO
THE UNCERTAINTIES ASSOCIATED WITH RAPID RAPID WEAKENING THAT
USUALLY FOLLOWS AFTER RAPID INTENSIFICATION. 

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