WDXS31 PGTW 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN)     
WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.5S 83.8E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 909 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
STEADILY WEAKENING SYSTEM WITH WARMING CLOUD TOP TEMPERATURES AND A
SMALLER, SHRINKING CONVECTIVE CORE. EIR IMAGERY, HOWEVER, STILL
REVEALS A 20NM ROUND EYE. THIS WEAKENING TREND IS EVIDENT IN A
262345Z SSMIS 91GHZ MICROWAVE IMAGE, WHICH SHOWS ERODING CONVECTIVE
BANDING OVER THE NORTHERN SEMICIRCLE AND A SMALL, NEARLY COMPLETE
EYEWALL SURROUNDING A MICROWAVE EYE FEATURE. THE SSMIS 37GHZ
IMAGERY SUGGESTS THAT THE LOW-LEVEL CIRCULATION CENTER MAY BE
DECOUPLING FROM THE UPPER-LEVEL CIRCULATION CENTER, HOWEVER, THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EIR
AND SSMIS IMAGERY. THE INITIAL INTENSITY OF 95 KTS IS ASSESSED WITH
HIGH CONFIDENCE BASED ON THE RANGE OF DVORAK CURRENT INTENSITY
ESTIMATES AS WELL AS ADT AND AIDT ESTIMATES FROM 92-94 KNOTS. A
262349Z RADARSAT SAR PASS SUPPORTS THE CURRENT POSITION WITHIN
ABOUT 10NM BUT ONLY SHOWS A MAXIMUM WIND SPEED OF 59 KNOTS, WHICH
APPEARS MUCH TOO LOW CONSIDERING THE PRESENCE OF AN EYE AND A
RECENT 261240Z RADARSAT SAR PASS SHOWING MAXIMUM WINDS OF 108
KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A
DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTHEAST
AND SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   FMEE: T5.5 - 102 KTS
   CIMSS SATCON: 103 KTS AT 261948Z
   CIMSS ADT: 92 KTS AT 262115Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TROPICAL CYCLONE (TC) 05S WILL TRACK STEADILY
WEST-SOUTHWESTWARD THROUGH TAU 48 ALONG THE NORTHWESTERN PERIPHERY
OF THE STR. AFTER TAU 48, THE SYSTEM WILL TURN SOUTHWESTWARD TO
SOUTH-SOUTHWESTWARD AS IT ROUNDS THE WESTERN PERIPHERY OF THE STR.
TC 05S WILL COMMENCE SUBTROPICAL TRANSITION NEAR TAU 72 AS IT
ENCOUNTERS INCREASING NORTHWESTERLIES ALONG THE LEADING EDGE OF AN
APPROACHING SUBTROPICAL TROUGH. ADDITIONALLY, INCREASING DRY AIR
ENTRAINMENT AND COOLING SST VALUES (24C) WILL SERVE TO
SIGNIFICANTLY WEAKEN THE SYSTEM. BY TAU 96, TC 05S WILL BECOME
EMBEDDED WITHIN THE SUBTROPICAL TROUGH AND COMPLETE SUBTROPICAL
TRANSITION.   

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.
OVERALL, THIS FORECAST IS HIGHLY CONSISTENT WITH THE PREVIOUS TRACK
FORECAST. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT WITH A 40-50
KNOT SPREAD IN GUIDANCE AT TAU 96. 

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