WDXS32 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE) WARNING NR 
020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.9S 69.2E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 771 NM SOUTHEAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
DEGRADING STRUCTURE, WITH DEEP CONVECTION SHEARING POLEWARD OF AN 
INCREASINGLY EXPOSED LOW-LEVEL CIRCULATION CENTER. THE INITIAL 
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON RECENT FIXES ON 
GEOSTATIONARY SATELLITE IMAGERY FROM PGTW AND KNES. THE INITIAL
INTENSITY OF 70 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A
CONSENSUS OF SUBJECTIVE DVORAK VALUES FROM PGTW, KNES, AND DEMS
(ALL AT T4.5) AND OBJECTIVE ESTIMATES FROM CIMSS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS ADT: 69 KTS AT 110600Z
   CIMSS AIDT: 64 KTS AT 110600Z
   CIMSS D-MINT: 66 KTS AT 110446Z
   CIMSS D-PRINT: 50 KTS AT 110600Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 STEADILY SOUTH-SOUTHEASTWARD
OVER THE NEXT 12 HOURS UNDER THE CONTINUED STEERING INFLUENCE OF THE
STR TO THE EAST. THEREAFTER, THE SYSTEM WILL ACCELERATE
SOUTH-SOUTHEASTWARD IN A TIGHTENING GRADIENT BETWEEN THE CURRENT
STEERING RIDGE AND A MID-LATITUDE TROUGH APPROACHING FROM THE
SOUTHWEST. FOR THE NEXT 24 HOURS, THE SYSTEM WILL WEAKEN STEADILY
UNDER THE INFLUENCE OF STRONG VERTICAL WIND SHEAR AND PASSAGE OVER
COOL WATER. THEREAFTER, FAVORABLE BAROCLINIC INTERACTION WITH THE 
APPROACHING TROUGH WILL SET A FLOOR TO THE INTENSITY AT AROUND 45 
KNOTS AND YIELD AN EXPANSION OF THE WIND FIELD AS THE SYSTEM 
COMPLETES EXTRATROPICAL TRANSITION. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN EXCELLENT AGREEMENT
REGARDING THE OVERALL FORECAST SCENARIO AS WELL AS THE ANTICIPATED
TRACK AND INTENSITY TRENDS. THERE IS HIGH CONFIDENCE IN BOTH THE
CURRENT TRACK AND INTENSITY FORECASTS.

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