WDXS32 PGTW 300900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12S (ELVIS) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.8S 44.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 352 NM SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY
COMPACT LOW LEVEL CIRCULATION CENTER (LLCC), AND A RESURGENCE OF
DEEP CONVECTIVE ACTIVITY AROUND THE LLCC OVER THE PAST SIX HOURS.
THE BULK OF THE CONVECTION IS CONFINED TO THE SOUTHWESTERN
QUADRANT OF THE LLCC AND EVEN NOW, AT 0700Z, THE CONVECTION IS
STARTING TO WANE A BIT, REVEALING THE TIGHT INNER SPIRAL OF THE
LLCC. THE INITIAL POSITION IS THUS ASSESSED WITH HIGH CONFIDENCE. A
LACK OF RECENT MICROWAVE AND WIND SPEED MEASUREMENTS MEANS THE
INITIAL INTENSITY ESTIMATE IS ASSESSED WITH LOW CONFIDENCE AND
HEDGED A BIT HIGHER THAN THE BULK OF THE SUBJECTIVE AND OBJECTIVE
INTENSITY ESTIMATES DUE TO THE EXTREMELY SMALL SIZE OF THE SYSTEM
AND CONSISTENT WITH THE PGTW T3.0 ESTIMATE. THE SYSTEM LIES OVER
RELATIVELY WARM WATERS, WHICH ARE CONTINUING TO PROVIDE AMPLE
ENERGY FLUX TO SUPPORT INTENSIFICATION. WHILE SHEAR IS STARTING TO
PICK UP A BIT, THE SYSTEM IS SITUATED AHEAD OF A DEEP 200MB TROUGH
AND AT THE BASE OF A STRONG JET MAXIMUM, LEADING TO A SIGNIFICANT
UPTICK IN POLEWARD OUTFLOW, WHICH IS OFFSETTING THE SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED NEAR THE MASCARENE ISLANDS

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS ADT: 30 KTS AT 300600Z
   CIMSS AIDT: 36 KTS AT 300600Z
   CIMSS D-MINT: 35 KTS AT 300306Z
   CIMSS D-PRINT: 31 KTS AT 300600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 12S (ELVIS) IS FORECAST TO TRACK
SOUTHEASTWARD FOR THE DURATION OF THE FORECAST PERIOD, ALONG THE
WESTERN SIDE OF A DEEP-LAYER STR CENTERED TO THE EAST, WITH NO
SIGNIFICANT CHANGES FROM THE PREVIOUS FORECAST. IN TERMS OF
INTENSITY, THE STRONG POLEWARD OUTFLOW IS FORECAST TO CONTINUE TO
OFFSET THE SLOWLY INCREASING SHEAR FOR THE NEXT 12 TO 18 HOURS,
WHILE THE SYSTEM REMAINS OVER RELATIVELY WARM OCEAN WATERS,
ALLOWING THE SYSTEM TO INTENSIFY SLIGHTLY DURING THE NEXT 12 HOURS.
THE NEGATIVE EFFECTS OF THE INCREASING SHEAR ARE EXPECTED TO
DOMINATE THE ROBUST OUTFLOW BY TAU 24, AND THE SYSTEM WILL BEGIN TO
SLOWLY WEAKEN AFTER THIS POINT. AT THE SAME TIME, TC 12S WILL BEGIN
EXTRATROPICAL TRANSITION (ETT) AS IT BECOMES EMBEDDED UNDER 500MB
TROUGH AXIS AND WORKS UNDER THE 200MB JET MAX. ETT IS EXPECTED TO
BE WRAPPED UP NO LATER THAN TAU 48, WITH ELVIS LEAVING THE BUILDING
AS A GALE-FORCE EXTRATROPICAL LOW.  

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
VERY GOOD AGREEMENT, WITH LITTLE IN THE WAY OF EITHER CROSS- OR
ALONG-TRACK SPREAD, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST.
INTENSITY GUIDANCE IS A MIXED BAG, WITH THE COAMPS-TC HOLDING THE
SYSTEM AT OR ABOVE 40 KNOTS THROUGH TAU 72, THE MESOSCALE GFS AND
HAFS-A TRACING A SINE WAVE PATTERN PEAKING AT 45KTS BY TAU 12, THEN
WEAKENING THROUGH TAU 48 FOLLOWED BY ADDITIONAL INTENSIFICATION
DRIVEN BY BAROCLINIC FORCING AFTER THE END OF THE FORECAST PERIOD.
FINALLY, THE SHIPS AND HWRF GUIDANCE DEPICT THE SYSTEM WEAKENING
BELOW WARNING CRITERIA WITHIN THE NEXT 24 HOURS. THE JTWC FORECAST
IS ROUGHLY BASED ON A BLEND OF THE HAFS-A, COAMPS-TC AND
PERSISTENCE. 
THANK YOU VERY MUCH. 

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