WDXS32 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.9S 85.7E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 762 NM WEST-SOUTHWEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A QUICKLY
DEVELOPING PINHOLE EYE FEATURE, IN A REPEAT OF 24 HOURS AGO, WHEN A
PINHOLE EYE EMERGED AT 0600Z. TC 13S (VINCE) REMAINS VERY COMPACT,
AND THE CYCLING CONVECTION HAS PERSISTED THROUGH THE LAST DAY,
SUCCESSFULLY PUSHING BACK AGAINST THE MODERATE EASTERLY SHEAR. A
LONG-TERM LOOP OF THE ENHANCED INFRARED (EIR) IMAGERY INDICATES THE
SYSTEM HAS BEEN FLIRTING WITH AN EYE THROUGH MOST OF THE DAY BUT
JUST LIKE YESTERDAY, THE EYE APPEARS TO HAVE PEAKED RIGHT AT
ANALYSIS TIME AND IS ALREADY FILLING IN A BIT. THE INITIAL POSITION
IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE NASCENT EYE FEATURE
AND EXTRAPOLATION OF A MICROWAVE EYE IN A 050357Z AMSU-B 89GHZ
IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, IN
LINE WITH THE HIGHER END OF THE ESTIMATES NOTED ABOVE. COINCIDENT
SAR PASSES FROM BOTH SENTINEL-1A AND RCM-2 SHOWED MAXIMUM WINDS OF
85 KNOTS AT THAT TIME AND THE SYSTEM HAS INTENSIFIED SINCE THEN.
RAW ADT VALUES BRIEFLY REACHED T6.3 BUT HAVE ALREADY COLLAPSED AS
THE EYE DISAPPEARS ONCE MORE. THE ENVIRONMENT IS FAVORABLE WITH
WARM SSTS, STRONG POLEWARD OUTFLOW AND LOW TO MODERATE EASTERLY
SHEAR.  THE LATEST CIMSS AMV ANALYSIS SUGGESTS THE UPPER-LEVEL FLOW
PATTERN IS BREAKING AROUND THE SYSTEM, REDUCING LOCALIZED SHEAR
EVEN FURTHER.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T5.0 - 90 KTS
   FMEE: T5.0 - 90 KTS
   CIMSS SATCON: 96 KTS AT 050645Z
   CIMSS ADT: 94 KTS AT 050615Z
   CIMSS AIDT: 89 KTS AT 050600Z
   CIMSS D-PRINT: 72 KTS AT 050600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG 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 WILL CONTINUE TO TRACK SOUTHWESTWARD
THROUGH TAU 96, ALONG THE NORTHERN SIDE OF A COMPLEX AND DYNAMIC
RIDGING PATTERN. TRACK SPEEDS WILL SLOW DOWN A KNOT OR TWO OVER THE
NEXT ONE TO TWO DAYS AS A MID-LATITUDE TROUGH PASSES BY TO THE
SOUTH. NOT STRONG ENOUGH TO INDUCE TC 13S SOUTHWARD, THE TROUGH
WILL BE STRONG ENOUGH TO BREAK THE RIDGE AND LOOSEN THE GRADIENT A
BIT. THE RIDGE BUILDS AND REPOSITIONS TO THE EAST OF TC 13S BY TAU
72 AND TRACK SPEEDS INCREASE ONCE AGAIN AS THE SYSTEM APPROACHES AN
INFLECTION POINT. TC 13S WILL TURN SHARPLY POLEWARD AFTER TAU 96,
AS IT QUICKLY ROUND THE AXIS OF THE STR WHICH WILL ALSO BE SLIDING
NORTHWARD SIMULTANEOUSLY. IN TERM OF INTENSITY, THE SYSTEM HAS
LIKELY ALREADY INTENSIFIED TO AT LEAST 100 KNOTS JUST SINCE
ANALYSIS TIME AS INDICATED BY THE LATEST ADT ESTIMATE OF 99 KNOTS.
ADDITIONAL INTENSIFICATION IS LIKELY, AS ANOTHER BURST OF DEEP
CONVECTION IS CURRENTLY DEVELOPING ON THE NORTHERN SIDE OF THE EYE
AND ROTATING UPSHEAR. HOWEVER, IT IS UNLIKELY THAT THE SYSTEM CAN
MAINTAIN 100-PLUS KNOT INTENSITY FOR LONG AS SHEAR IS FORECAST TO
INCREASE A NOTCH AFTER TAU 48, AND EYEWALL REPLACEMENT CYCLES
PRESENT AN EVER-PRESENT POSSIBILITY. STEADY-STATE INTENSITY AROUND
90-95 KNOTS IS FORECAST FROM 48 TO 72 HOURS OUT, AS COMPETING
ENVIRONMENTAL FACTORS WILL OFFSET ONE ANOTHER. A WEAKENING OF THE
DEEP-LAYER SHEAR AND IN INCREASE IN SSTS AND POLEWARD OUTFLOW
SHOULD FUEL A SLIGHT INTENSIFICATION UP THROUGH TAU 96. RAPID
WEAKENING IS EXPECTED AFTER TAU 96 AS THE SYSTEM WILL FACE RAPIDLY
INCREASING SHEAR, SIGNIFICANT DRY AIR ENTRAINMENT AND COOLING SSTS
AS IT SHIFTS QUICKLY POLEWARD.  

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS GOOD AGREEMENT
THROUGH TAU 96, WITH 100NM CROSS-TRACK SPREAD AT TAU 96.
ALONG-TRACK SPREAD BEGINS TO INCREASE AFTER TAU 72 BUT IS
RELATIVELY MINOR UNTIL AFTER TAU 96. BY TAU 120, CROSS-TRACK SPREAD
INCREASES MARGINALLY TO ABOUT 115NM, THOUGH ALONG-TRACK UNCERTAINTY
INCREASES SHARPLY TO 215NM. THE JTWC FORECAST IS SITUATED ON THE
NORTHERN EDGE OF THE GUIDANCE ENVELOPE THROUGH TAU 96, WITH HIGH
CONFIDENCE. AFTER THIS POINT, THE FORECAST TRACK MOVES IN TOWARDS
THE CONSENSUS MEAN, GENERALLY TOWARDS THE SLOWER MODELS, WITH
MEDIUM CONFIDENCE. THE JTWC INTENSITY FORECAST DEVIATES FROM THE
GUIDANCE IN THE NEAR-TERM, AS ALL MODELS INDICATE A SHARP WEAKENING
FROM TAU 00, WHILE THE JTWC FORECAST INCREASES THE INTENSITY. BY
TAU 48, THE JTWC FORECAST REJOINS THE HAFS-A FORECAST AND REMAINS
CONSISTENT WITH THE HAFS-A AND CONSENSUS MEAN, ON THE HIGHER END OF
THE GUIDANCE, THROUGH THE REMAINDER OF THE FORECAST. 

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