WDXS32 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.8S 78.3E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 833 NM SOUTH-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 13S (VINCE) WITH A VERY SYMMETRICAL AND COMPACT CENTRAL
DENSE OVERCAST (CDO) SURROUNDING THE EYEWALL OF A WELL-DEFINED 20
NM EYE. CLOUD TOPS HAVE SLIGHTLY WARMED OVER THE PAST 6 HOURS.
ENVIRONMENTAL ANALYSIS INDICATES THAT 13S IS IN A HIGHLY FAVORABLE
ENVIRONMENT CHARACTERIZED BY STRONG RADIAL OUTFLOW, LOW (5-10 KTS)
VERTICAL WIND SHEAR, AND WARM (27-28 C) SEA SURFACE TEMPERATURES.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
DEFINED EYE IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 130 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND
OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED 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: T6.5 - 127 KTS
   CIMSS ADT: 127 KTS AT 070600Z
   CIMSS AIDT: 131 KTS AT 070600Z
   CIMSS DPRINT: 121 KTS AT 070600Z

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

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: 13S IS FORECAST TO CONTINUE TRACKING GENERALLY
WESTWARD, ALONG THE NORTHERN PERIPHERY OF THE STR THROUGH TAU 48.
AROUND TAU 48, THE RIDGE REORIENTS TO A NORTH-SOUTH ALIGNMENT,
CAUSING THE SYSTEM TO TRACK SOUTHWARD THROUGH TAU 96. AFTER TAU 96,
THE SYSTEM WILL TRACK MORE SOUTH-SOUTHEASTWARD AS IT BEGINS TO
ROUND THE RIDGE AXIS. REGARDING INTENSITY, 13S IS FORECAST TO BEGIN
GRADUALLY WEAKENING OVER THE NEXT 48 HOURS IN RESPONSE TO AN
INCREASE IN VERTICAL WIND SHEAR. AFTER TAU 48, AS THE SYSTEM TRACKS
SOUTHWARD, ENVIRONMENTAL PARAMETERS WILL QUICKLY WORSEN. NAMELY SEA
SURFACE TEMPERATURES WILL DROP TO AROUND 24C AT TAU 96. AS A
RESULT, TC 13S WILL WEAKEN THROUGHOUT THE REMAINDER OF THE FORECAST
PERIOD. EXTRATROPICAL TRANSITION IS FORECAST TO BEGIN AROUND TAU
120 AS THE SYSTEM STARTS TO INTERACT WITH THE JET AND ENTERS THE
BAROCLINIC ZONE. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY GOOD
AGREEMENT REGARDING THE TRACK OF 14S WITH A 60 NM CROSS-TRACK
SPREAD AT TAU 72. ALONG-TRACK SPREAD DOES INCREASE AFTER TAU 72,
BUT MODELS CONTINUE TO HIGHLY AGREE REGARDING CROSS-TRACK SPREAD.
THE JTWC TRACK FORECAST IS PLACED CLOSE TO CONSENSUS WITH OVERALL
HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD AGREEMENT, WITH THE
EXCEPTION OF GFS WHICH REPRESENTS THE VORTEX MUCH WEAKER THROUGH
TAU 72. ALL OTHER MODELS ARE IN CLOSE PROXIMITY AND SUGGEST A
GRADUAL WEAKENING TREND. THE JTWC INTENSITY FORECAST IS STILL ONLY
PLACED WITH MEDIUM CONFIDENCE DUE TO THE LOW SKILL THE MODELS HAVE
HAD REGARDING INTENSIFICATION TRENDS FOR THE SYSTEM.

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