WDXS32 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE) WARNING NR 
019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.9S 68.5E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 684 NM EAST-SOUTHEAST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 13S DEGRADING AS STRONG 20-25KT VERTICAL WIND SHEAR
FROM THE NORTHWEST INDUCES A SIGNIFICANT VERTICAL TILT WITH HEIGHT,
NEARLY EXTINGUISHING THE EYE FEATURE. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED ANIMATED
EIR AND A 101711Z METOP-B ASCAT IMAGE REVEALING A BULLS-EYE LOW-LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL INTENSITY IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED
BELOW ACCOMPANIED BY THE DETERIORATING STRUCTURE OF TC 13S.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T5.0 - 90 KTS
   DEMS: T5.5 - 102 KTS
   FIMP: T5.0 - 90 KTS
   CIMSS SATCON: 96 KTS AT 101830Z
   CIMSS ADT: 94 KTS AT 101800Z
   CIMSS AIDT: 87 KTS AT 101830Z
   CIMSS D-PRINT: 72 KTS AT 101830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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 BE DRIVEN SOUTHWARD CONTINUING TO
ROUND THE SUBTROPICAL RIDGE. THE TRACK SPEED WILL REMAIN CONSISTENT
BETWEEN 10-15KTS UNTIL AN UPPER-LEVEL TROUGH CAUSES THE SYSTEM TO
UNDERGO EXTRATROPICAL TRANSITION STARTING AT TAU 48, AND FULLY
COMPLETING BY TAU 72. THE TRACK SPEED BY THE END OF THE FORECAST
WILL BE 35KTS POLEWARD. TC 13S IS ANTICIPATED TO CONTINUE TO WEAKEN
FOR THE REMAINDER OF THE FORECAST PERIOD. MODERATE VERTICAL WIND
SHEAR WILL CONTINUE TO ERODE THE SYSTEM FOR THE NEXT 36 HOURS. THE
UPPER-LEVEL TROUGH AND COOL SEA SURFACE TEMPERATURES THAT WILL MEET
TC 13S BETWEEN TAU 48-72 WILL INITIATE EXTRATROPICAL TRANSITION AND
CAUSE THE SYSTEM TO GO THROUGH A BRIEF SUBTROPICAL PHASE PRIOR TO
BECOMING STRONGLY BAROCLINIC AND FULLY EXTRATROPICAL AT TAU 72. THE
BAROCLINIC FORCING WILL RESULT IN A SLIGHT INTENSIFICATION BETWEEN TAU 
48-72.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG
AGREEMENT THAT THE SYSTEM WILL REMAIN UNDER THE STEERING INFLUENCE
OF THE STR TO THE EAST. THE CROSS-TRACK SPREAD BY TAU 72 IS 140NM,
FURTHER SUPPORTING THE HIGH CONFIDENCE IN THE TRACK. THE JTWC
MULTI-MODEL CONSENSUS GUIDANCE IS IN STRONG AGREEMENT THAT THE
SYSTEM WILL WEAKEN TO 45KTS AT TAU 48 BEFORE SLIGHTLY INCREASING.

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