WDXS32 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE) WARNING NR 
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.6S 69.3E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 679 NM EAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 41 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A NEARLY
SYMMETRICAL, TIGHTLY ORGANIZED TROPICAL CYCLONE (TC) 13S (VINCE).
FOLLOWING THE LIKELY EYEWALL REPLACEMENT CYCLE, THE EYE HAS
TIGHTENED TO ABOUT 25-30NM IN DIAMETER, AS PRESENT IN THE ENHANCED
INFRARED IMAGERY, AS WELL AS THE 091351Z F16 SSSMIS 91 GHZ IMAGE.
ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY FAVORABLE, WITH WARM
(26-27C) SEA SURFACE TEMPERATURES, WEAK (10-15KTS) VERTICAL WIND
SHEAR (VWS) AND GOOD OUTFLOW. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE CLEAR AND SYMMETRICAL EYE FEATURE. THE
INITIAL INTENSITY OF 105 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED
ON THE AGENCY FIXES AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE EAST, EXTENDING SOUTHWESTWARD

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T6.0 - 115 KTS
   FMEE: T6.0 - 115 KTS
   FIMP: T6.0 - 115 KTS
   CIMSS SATCON: 97 KTS AT 091648Z
   CIMSS ADT: 99 KTS AT 091800Z
   CIMSS AIDT: 100 KTS AT 091800Z
   CIMSS D-PRINT: 99 KTS AT 091900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: STRONG POLEWARD CHANNEL OUTFLOW

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: TC 13S IS FORECAST TO CONTINUE TRANSITING ALONG 
THE WESTERN PERIPHERY OF THE STR TO THE EAST-SOUTHEAST THROUGHOUT THE 
FORECAST PERIOD. WHILE IT IS CURRENTLY HEADING SOUTHWESTWARD, AROUND 
TAU 24 IT IS EXPECTED TO BEGIN TURNING SOUTH-SOUTHEASTWARD. AT TAU 48, 
TC VINCE IS FORECAST TO BEGIN ITS SUBTROPICAL TRANSITION. INTENSITY 
FORECAST CALLS FOR SLOW INITIAL WEAKENING, HOWEVER AS THE SYSTEM GETS 
CLOSER TO THE 26C ISOTHERM, THE ENVIRONMENTAL CONDITIONS WILL BEGIN TO 
RAPIDLY ERODE. VERTICAL WIND SHEAR IS EXPECTED TO INCREASE TO 40+ 
KNOTS, WHILE A MID-LEVEL PUSH OF DRY AIR FROM THE WEST WILL FURTHER 
HINDER ANY POTENTIAL REDEVELOPMENT. THE SYSTEM IS EXPECTED TO COMPLETE 
THE SUBTROPICAL TRANSITION BY THE END OF THE FORECAST PERIOD, PRIOR TO 
BEING COMPLETELY ABSORBED BY THE ATMOSPHERIC FLOW WITHIN BAROCLINIC 
ZONE TO THE SOUTH.

MODEL DISCUSSION: DETERMINISTIC NUMERICAL MODEL GUIDANCE REMAINS IN
GOOD AGREEMENT, BOTH IN REGARD TO TRACK AND INTENSITY, WITH ALL
MODEL TRACKERS SHOWING SIMILAR CURVATURE OF THE TURN, AS WELL AS
SIMILAR GRADE OF WEAKENING. THE CROSS TRACK SPREAD AT THE END OF
THE FORECAST PERIOD IS 65NM. JTWC FORECAST IS THEN LAID IN CLOSE
PROXIMITY TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE.

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