WDXS33 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (TALIAH) WARNING NR 
025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0S 87.2E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 809 NM SOUTHWEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED
LOW LEVEL CIRCULATION CENTER (LLCC), WITH WEAK CONVECTION CONFINED
TO THE SOUTHEASTERN SECTOR OF THE ROTATION. A 130338Z AMSU-B 89GHZ
MICROWAVE IMAGE DEPICTED A SYMMETRIC LOW-LEVEL STRUCTURE, WITH
SHALLOW RAINBANDS WRAPPING INTO A DEFINED LLCC BUT FOR THE MOST
PART THE CIRCULATION WAS DEVOID OF SIGNIFICANT CONVECTION. AN
EARLIER RCM-2 SAR PASS REVEALED WINDS OF 64 KNOTS IN THE
SOUTHEASTERN QUADRANT, BUT THE REMAINDER OF THE WIND FIELD WAS
ABOUT 60 KNOTS OR LESS. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC IN THE MSI. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF
THE OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES NOTED ABOVE. THE
ENVIRONMENT IS MARGINAL, WITH LOW TO MODERATE NORTHERLY SHEAR,
MARGINAL SSTS OF 25-26C AND STRONG POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T4.5 - 77 KTS
   FIMP: T4.0 - 65 KTS
   CIMSS SATCON: 60 KTS AT 130515Z
   CIMSS ADT: 32 KTS AT 130615Z
   CIMSS AIDT: 51 KTS AT 130615Z
   CIMSS D-PRINT: 47 KTS AT 130615Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR TO THE NORTHWEST.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 14S WILL CONTINUE TO TRACK TOWARDS THE
SOUTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP STR TO THE
EAST FOR THE NEXT 24 HOURS. TRACK SPEEDS BEGIN TO SLOW DOWN AS
EARLY AS TAU 12, BUT THE BRAKES ARE REALLY APPLIED AFTER ABOUT TAU
24, WHEN A MID-LATITUDE TROF WILL PASS BY TO THE SOUTH AND BREAK
DOWN THE RIDGING PATTERN. THE TROF IS NOT EXPECTED TO BE STRONG
ENOUGH TO PULL TC 14S POLEWARD BUT THE SYSTEM SLOWS TO JUST 4-5
KNOTS THROUGH TAU 48 IN THIS WEAKENED STEERING PATTERN. THE TROF IS
QUICKLY REPLACED BY A TRANSIENT RIDGE QUICKLY MOVING EASTWARD TO
THE SOUTH OF TC 14S. THIS RIDGE REMAINS SOUTH OF TC 14S THROUGH
ABOUT TAU 72 AND THE SYSTEM WILL PICK UP SPEED ONCE AGAIN DURING
THIS TIMEFRAME BUT REMAIN TRACKING TOWARDS THE SOUTHWEST. ANOTHER
TROF WILL PASS BY TO SOUTH AROUND TAU 96, GENERATING ANOTHER WEAK
STEERING PATTERN, WITH THE RESULTANT SLOWDOWN IN TRACK SPEEDS AFTER
TAU 96. THIS TROF MAY BE STRONG ENOUGH TO PULL TC 14S POLEWARD,
THOUGH THERE IS A HIGH DEGREE OF UNCERTAINTY BETWEEN THE MODELS ON
THE STRENGTH OF THE TROF AND HOW MUCH OF AN IMPACT IT WILL HAVE. TC
14S WILL SLOWLY BUT STEADILY WEAKEN 36 HOURS DUE TO PERSISTENT
MODERATE SHEAR, MARGINAL SSTS AND DRY MID-LEVEL AIR INTRUSION. A
BRIEF PERIOD OF REINTENSIFICATION IS EXPECTED BETWEEN TAU 48 AND 72
AS THE SYSTEM TAPS INTO A ROBUST POLEWARD OUTFLOW CHANNEL, WHILE
THE OTHER ENVIRONMENTAL FACTORS REMAIN RELATIVELY STEADY-STATE. THE
SYSTEM QUICKLY WEAKENS AFTER TAU 72 AS IT MOVES INTO STEADILY
COOLER WATERS, AND BOTH SHEAR AND DRY AIR INCREASE. THE SYSTEM IS
PREDICTED TO REMAIN WARM CORE THROUGHOUT THE FULL FORECAST PERIOD
AND NO SUBTROPICAL OR EXTRATROPICAL TRANSITION IS FORECAST.  

MODEL DISCUSSION: THE BULK OF THE DETERMINISTIC TRACK GUIDANCE IS
CONFINED TO A VERY TIGHT ENVELOPE, EXPANDING TO JUST 90NM BY TAU
120. THE ONLY OUTLIERS ARE THE ECMWF AND ECEPS MEAN, WHICH BREAK
FROM THE REST OF THE PACK AFTER TAU 96 AND TURN THE SYSTEM MORE
POLEWARD AND INTO THE TROF THAT PASSES BY AROUND THIS TIMEFRAME.
EVERY OTHER MODEL DEPICTS A STRAIGHT SOUTHWESTWARD TRACK THROUGH
THE FORECAST PERIOD, THOUGH ALL AGREE THAT THE SYSTEM SLOWS SHARPLY
BY THE TAU 120. AS ONE MIGHT EXPECT, BOTH THE ECEPS AND GEFS
ENSEMBLE MEMBERS SHOW INCREASED DISPERSION AFTER TAU 72, WITH
SEVERAL MEMBERS OF BOTH MODELS DEPICTING A TURN POLEWARD AFTER ABOUT
TAU 96. THE JTWC FORECAST CLOSELY FOLLOWS THE CONSENSUS MEAN
THROUGH THE ENTIRE FORECAST, WITH HIGH CONFIDENCE TO TAU 72,
DECREASING TO MEDIUM IN THE LONG-TERM. INTENSITY GUIDANCE IS IN
RELATIVELY GOOD AGREEMENT, WITH ALL OF THE MESOSCALE MODELS
DEPICTING A WEAKENING TREND TO TAU 36, FOLLOWED BY
REINTENSIFICATION TO A PEAK BETWEEN 50-65 KNOTS AROUND TAU 72,
FOLLOWED BY RAPID WEAKENING THEREAFTER. THE JTWC FORECAST GENERALLY
FOLLOWS THE CONSENSUS MEAN TREND LINE, BUT IS SITUATED ABOUT 5
KNOTS HIGHER THROUGH MOST OF THE FORECAST PERIOD. 

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