WDXS32 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE) WARNING NR 
021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.9S 70.1E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 875 NM SOUTHEAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 13S (VINCE) WITH A RAPIDLY DISSIPATING STRUCTURE WHILE
ALL SUPPORTIVE CONVECTION HAS BECOME SHEARED TO THE SOUTHERN
SEMICIRCLE OVER THE LAST FEW HOURS. THE LOW-LEVEL CIRCULATION
CENTER (LLCC) IS NOW COMPLETELY EXPOSED AS DRY AIR HAS CONTINUED TO
WRAP INTO THE CORE FROM THE NORTHERN QUADRANT WHILE THE SYSTEM NEARS
THE MID-LATITUDE WESTERLIES TO THE SOUTH. UPPER-LEVEL SUPPORT HAS
CONTINUED TO SUSTAIN ENHANCED SURFACE INTENSITIES, WITH MODERATE
POLEWARD OUTFLOW INDICATED ON ANIMATED WATER VAPOR IMAGERY. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
EVIDENT AND FULLY EXPOSED LLCC INDICATED ON ANIMATED EIR SATELLITE 
IMAGERY AND AN 111744Z ASCAT-C PASS. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN EARLIER 111357Z RCM-2 SAR 
IMAGE SHOWING SUSTAINED AND ENHANCED SURFACE INTENSITIES IN CLOSE 
PROXIMITY TO THE LLCC.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE DIRECTLY TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 57 KTS AT 111830Z
   CIMSS ADT: 35 KTS AT 111830Z
   CIMSS AIDT: 44 KTS AT 111830Z
   CIMSS D-MINT: 44 KTS AT 111556Z
   CIMSS D-PRINT: 39 KTS AT 111830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30+ KTS
   SST: 24-25 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 13S IS FORECASTED TO CONTINUE TRACKING
ANTICYCLONICALLY ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE LOCATED DIRECTLY TO THE EAST THROUGHOUT THE 36 HOUR FORECAST
PERIOD. BETWEEN TAU 24 AND TAU 36, THE CYCLONE IS EXPECTED TO
ACCELERATE SOUTHEASTWARD AS AN EQUATORWARD EXTENDING LONGWAVE
TROUGH APPROACHES FROM THE WEST, ASSISTING IN THE QUICKENED POLEWARD
MOVEMENT. THROUGH TAU 24, THE CYCLONE WILL STEADILY WEAKEN TO 50
KTS DUE TO CONTINUED HIGH VERTICAL WIND SHEAR (VWS) OF OVER 30 KTS
AND SEA SURFACE TEMPERATURES (SST) BELOW 26 C. BETWEEN TAU 24 AND
TAU 36, THE SYSTEM IS FORECASTED TO BEGIN EXTRATROPICAL TRANSITION
WITH INCREASED INFLUENCES FROM THE MIDLATITUDE BAROCLINIC
WESTERLIES. DURING THIS TRANSITION, A BROADENING SURFACE WIND FIELD
WITH MAXIMUM INTENSITIES OF 45 KTS IS FORECASTED UNTIL THE SYSTEM 
COMPLETES EXTRATROPICAL TRANSITION BY TAU 36. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY TIGHT
AGREEMENT WITH REGARD TO THE FORECASTED TRACK AND INTENSITY
THROUGHOUT THE 36 HOUR PERIOD. THE CROSS-TRACK SPREAD REMAINS LESS
THAN 90 NM UNTIL THE COMPLETION OF EXTRATROPICAL TRANSITION, WHILE
THE JTWC INTENSITY GUIDANCE IS IN AGREEMENT THAT STEADY WEAKENING
WILL OCCUR UNTIL TAU 36. THERE IS HIGH CONFIDENCE IN THE JTWC TRACK
AND INTENSITY FORECASTS. 

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