WDXS32 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.1S 75.9E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 805 NM SOUTH-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 52 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 13S WITH A 13NM WIDE CLEARING EYE FEATURE. WATER VAPOR
IMAGERY HIGHLIGHTS THE POINT SOURCE ALOFT AND STRONG DIVERGENT
EXHAUST. THE CLOUD TOPS ALOFT REVEAL WARMING CLOUD TOPS AND A
NEARLY ANNULAR SETUP FOR EYEWALL REPLACEMENT TO OCCUR IN THE NEAR
FUTURE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON AFOREMENTIONED IMAGERY. THE INITIAL INTENSITY OF 130 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE
FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: A LOBE OF A SUBTROPICAL RIDGE (STR) TO
THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   KNES: T7.0 - 140 KTS 
   DEMS: T7.0 - 140 KTS 
   FMEE: T7.0 - 140 KTS 
   FIMP: T7.0 - 140 KTS 
   CIMSS SATCON: 126 KTS AT 071405Z
   CIMSS ADT: 129 KTS AT 071800Z
   CIMSS AIDT: 132 KTS AT 071900Z
   CIMSS D-PRINT: 127 KTS AT 071900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 13S WILL TRACK WEST-SOUTHWESTWARD UNDER THE
STEERING INFLUENCE OF AN ELONGATED SUBTROPICAL RIDGE LOCATED TO THE
SOUTH. THE RIDGE WILL MOVE EASTWARD AND STEERING WILL BE PICKED UP
BY A DIFFERENT SUBTROPICAL RIDGE, CAUSING THE TRACK TO SHARPLY
CURVE SOUTHWARD BETWEEN TAU 36 AND 72. THE SYSTEM WILL CONTINUE TO
ROUND THE RIDGE FOR THE REMAINDER OF THE FORECAST PERIOD. IN THE
NEAR-TERM FORECAST, THE SLOW TRACK SPEED OF THE SYSTEM WILL RESULT IN
UPWELLING, WHICH WILL INITIATE WEAKENING WITHIN THE FIRST 24 HOURS.
VERTICAL WIND SHEAR WILL ALSO INCREASE STARTING AT TAU 36,
FURTHERING THE RATE OF WEAKENING FOR THE REMAINDER OF THE FORECAST.
SEA SURFACE TEMPERATURES ARE EXPECTED TO BE FAVORABLE ABOVE 26C
UNTIL TAU 72. COOL SEA SURFACE TEMPERATURES AND AN UPPER-LEVEL
TROUGH WILL RESULT IN EXTRATROPICAL TRANSITION THAT IS EXPECTED TO
COMPLETE BY TAU 120.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG
AGREEMENT THAT THE SYSTEM WILL WEAKLY AND SLOWLY TRACK WESTWARD
BEFORE CURVING SOUTH. THE INTENSITY GUIDANCE IS ALSO IN GOOD
AGREEMENT REGARDING CONSISTENT WEAKENING. ONE OUTLIER IS GFS, WHICH
FORECASTS RAPID WEAKENING WITHIN THE FIRST 24 HOURS.

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