WDXS32 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (SEAN) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.5S 113.3E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 117 NM NORTH-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT AND TIGHTLY ORGANIZED TC 10S (SEAN), WITH A DEVELOPING 
PINHOLE, RAGGED EYE, SURROUNDED BY COLD CLOUD TOPS. ENVIRONMENTAL 
CONDITIONS ARE HIGHLY FAVORABLE WITH HIGH SEA SURFACE TEMPERATURES 
(SST), LOW VERTICAL WIND SHEAR (VWS), AND STRONG RADIAL OUTFLOW. THE 
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EIR AND 
ANIMATED RADAR IMAGERY DEPICTING A DEVELOPING EYE. THE INITIAL
INTENSITY OF 75 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
THE IMPROVED APPEARANCE, AS WELL AS THE AUTOMATED CIMSS INTENSITY 
ESTIMATES AND AGENCY FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE, SCATTEROMETER DATA AND
SURFACE OBSERVATIONS

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.5 - 77 KTS
   APRF: T4.0 - 65 KTS
   CIMSS ADT: 79 KTS AT 191800Z
   CIMSS AIDT: 78 KTS AT 191800Z
   CIMSS D-MINT: 86 KTS AT 191806Z
   CIMSS D-PRINT: 78 KTS AT 191800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 10S IS FORECAST TO CONTINUE TRACKING ALONG
THE NORTHWESTERN PERIPHERY OF THE STR OVER WESTERN AUSTRALIA.  AS 
ENVIRONMENTAL PARAMETERS REMAIN HIGHLY FAVORABLE OVER THE NEXT 24 
HOURS, TC 10S IS EXPECTED TO CONTINUE RAPID INTENSIFICATION REACHING 
PEAK INTENSITY OF 90 KTS NEAR TAU 24. AS 10S GETS CLOSER TO THE STR 
AXIS, ENVIRONMENTAL CONDITIONS WILL START TO QUICKLY WORSEN, LEADING 
TO A RAPID WEAKENING OF THE CYCLONE. AT TAU 96 TC 10S IS FORECAST TO 
BEGIN DISSIPATION, DUE TO THE INCREASINGLY STRONG DRY AIR
INTRUSION. AS THE SYSTEM DISSIPATES, IT WILL SIMULTANEOUSLY BE 
TRANSITIONING INTO AN EXTRATROPICAL CYCLONE. THE CURRENT FORECAST 
CALLS FOR DISSIPATION AT TAU 120, BEFORE EXTRATROPICAL TRANSITION CAN 
COMPLETE.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT THROUGH TAU 72, WITH A CROSS-TRACK SPREAD OF 150 NM, WITH
ONE OUTLIER IN THE FORM OF GALWEM, WHICH SUGGESTS A TIGHTER TURN
(CLOSER TO THE SOUTHWESTERN COAST OF AUSTRALIA). AFTER TAU 72
MAJORITY OF THE CONSENSUS MEMBERS ARE STILL IN A GOOD AGREEMENT IN
REGARD TO THE TRACK AND EVENTUAL DISSIPATION OF TC 10S. HOWEVER,
UKMET ENSEMBLE SLOWS CONSIDERABLY AFTER TAU 72, AND BECOMES THE 
PRIMARY OUTLIER THEREAFTER. JTWC TRACK FORECAST IS THEREFORE LAID WITH 
OVERALL MEDIUM CONFIDENCE AND SLIGHTLY TO THE EAST OF THE
CONSENSUS TRACK. INTENSITY GUIDANCE IS ASSESSED WITH MEDIUM
CONFIDENCE, AS ALL AIDS ARE CONSISTENT WITH THE GENERAL
INTENSIFICATION AND WEAKENING TRENDS, WITH THE EXCEPTION OF COAMPS-TC. 
COAMPS-TC SUGGESTS STEADY WEAKENING THROUGH TAU 24 VICE 
INTENSIFICATION. THE JTWC INTENSITY FORECAST IS INITIALLY HIGHER THAN 
THE CONSENSUS, DUE TO HEAVILY FAVORABLE ENVIRONMENT, BUT FOLLOWING THE
PEAK AROUND TAU 24, IT IS IN CLOSE PROXIMITY TO CONSENSUS.

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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