WDXS32 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE)      
WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.7S 80.7E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 1319 NM EAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 37 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 13S HAS RAPIDLY INTENSIFIED OVER THE PAST 24
HOURS FROM 105 KNOTS AT 051800Z TO THE CURRENT INTENSITY OF 135 KNOTS. 
AS INDICATED IN THE ANIMATED ENHANCED INFRARED (EIR) SATELLITE 
IMAGERY, TC 13S HAS MAINTAINED A VERY SMALL (80NM DIAMETER) 
AXISYMMETRIC CONVECTIVE CORE, WITH AN 18NM ROUND EYE (EYE TEMPERATURE 
PLUS 16C) AND WEAK SPIRAL BANDING OVER THE SOUTHEAST QUADRANT. 
ALTHOUGH THE SYSTEM HAS AN ANNULAR-LIKE APPEARANCE, THE PRESENCE OF 
THE SPIRAL BAND AND THE NON-UNIFORM CLOUD-TOP TEMPERATURES DO NOT 
CHARACTERIZE AN ANNULAR SYSTEM AT THIS TIME. THE INITIAL POSITION IS 
PLACED WITH HIGH CONFIDENCE BASED ON THE ROUND EYE IN EIR IMAGERY. THE 
INITIAL INTENSITY OF 135 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON 
THE AGENCY DVORAK ESTIMATES RANGING FROM 127 TO 140 KNOTS (LONE 
EXCEPTION IS FIMP'S T6.0 ESTIMATE, WHICH APPEARS TOO LOW). THE INITIAL 
INTENSITY ASSESSMENT IS ALSO SUPPORTED BY THE CIMSS 061800Z ADT, AIDT 
ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) 
POSITIONED TO THE SOUTH, WITH A SLIGHT BREAK ASSOCIATED WITH A MAJOR 
SHORTWAVE TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   KNES: T6.5 - 127 KTS
   DEMS: T7.0 - 140 KTS 
   FMEE: T6.5 - 127 KTS
   FIMP: T6.0 - 115 KTS
   CIMSS SATCON: 127 KTS AT 061800Z
   CIMSS ADT: 132 KTS AT 061800Z
   CIMSS AIDT: 132 KTS AT 061800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: DUE TO THE RAPID INTENSIFICATION PHASE, 
THE SHORT-TERM INTENSITY FORECAST IS SIGNIFICANTLY HIGHER THAN THE
PREVIOUS FORECAST. 

FORECAST DISCUSSION: THE MAJOR SHORTWAVE TROUGH ASSOCIATED WITH THE
SHRINKING BREAK TO THE SOUTH IS FILLING, WITH THE JET MAX LOCATED ON 
THE EASTERN SIDE OF THE TROUGH, AND PROPAGATING QUICKLY EASTWARD. 
CONSEQUENTLY, THE STR IS EXPECTED TO STRENGTHEN DRIVING THE SYSTEM 
WESTWARD THROUGH TAU 48. DUE TO HIGHLY FAVORABLE ENVIRONMENTAL 
CONDITIONS AND THE COMPACT NATURE OF THE INSULATED CORE, TC 13S SHOULD 
MAINTAIN SUPER TYPHOON STRENGTH WINDS (130-140 KNOTS) THROUGH TAU 36. 
HOWEVER, THE VERY SMALL SYSTEM IS SUSCEPTIBLE TO RAPID FLUCTUATIONS IN 
INTENSITY THROUGH TAU 48. AFTER TAU 48, THE STEERING RIDGE WILL RE-
ORIENT NORTH-SOUTH, WITH A BROAD UPPER-LEVEL SUBTROPICAL TROUGH 
DIGGING EQUATORWARD AND ENVELOPING THE SYSTEM, WHICH WILL DRIVE THE 
SYSTEM SOUTHWARD THROUGH TAU 120. ENVIRONMENTAL CONDITIONS WILL 
DEGRADE IN THE EXTENDED PERIOD LEADING TO A PRONOUNCED WEAKENING 
TREND, WITH INCREASING (30-35 KNOTS) VERTICAL WIND SHEAR AND COOLING 
SST VALUES (24-25C).     

MODEL DISCUSSION: GLOBAL MODEL GUIDANCE IS IN FAIR AGREEMENT THROUGH 
THE FORECAST PERIOD, WITH A 90NM TO 150NM CROSS-TRACK SPREAD FROM TAU 
72 TO TAU 120. EPS AND GEFS ENSEMBLE GUIDANCE SHOWS A SLIGHTLY WIDER 
SPREAD OF SOLUTIONS BUT REMAINS IN OVERALL GOOD AGREEMENT LENDING 
MEDIUM CONFIDENCE TO THE JTWC FORECAST. RELIABLE INTENSITY GUIDANCE 
REMAINS IN FAIR AGREEMENT ALTHOUGH THERE IS SIGNIFICANT UNCERTAINTY IN 
THE INTENSITY FORECAST DUE TO THE COMPACT NATURE OF THE SYSTEM.    

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