WDPS31 PGTW 272100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 15P (JUDY) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.6S 169.2E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 251 NM NORTH-NORTHEAST OF PORT VILA,
VANUATU
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
CONSOLIDATING SYSTEM, WITH A LARGE CENTRAL COLD COVER (CCC)
FEATURE. A 271618Z SSMIS COLORIZED 89GHZ MICROWAVE IMAGE SHOWED
WHAT APPEARS TO BE THE LLCC DISPLACED SOUTH OF THE DEEPEST
CONVECTION, AT LEAST AT THAT TIME. THE CCC IS MAKING ANALYSIS OF
THE CENTER POSITION AND ACTUAL INTENSITY RATHER CHALLENGING, BUT A
RECENT INNER CORE LIGHTNING BURST AND HOT TOWERS APPROACHING -100C
ARE PROVIDING SOME ADDITIONAL CLARITY TO THE LIKELY INITIAL
POSITION, AND BASED OFF THE IR SIGNATURE, IT IS LIKELY THE LLCC HAS
ALREADY TUCKED UNDER THE CONVECTION. THE INITIAL POSITION IS THUS
ASSESSED WITH MEDIUM CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED
AT 50 KNOTS, HEDGED ABOVE THE MAJORITY OF THE AGENCY DVORAK CURRENT
INTENSITY ESTIMATES (EXCEPT PHFO AND NFFN AT T3.5) WHO ARE HOLDING
AT T2.5 DUE TO USAGE OF THE CCC METHOD, AND MORE IN AGREEMENT WITH
THE SATCON, ADT, DEEP MICRONET AND OPEN-AIIR. THE SYSTEM IS MOVING
SLOWLY SOUTHWESTWARD AS IT BEGINS TO ROUND THE RIDGE AXIS.
ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE AT THE MOMENT, WITH
VERY WARM (30-31C) SSTS, STRONG EQUATORWARD OUTFLOW, LOW VWS AND
VERY HIGH OHC (165 KJ PER CM2).

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   PHFO: T3.5 - 55 KTS
   NFFN: T3.5 - 55 KTS
   CIMSS SATCON: 52 KTS AT 271412Z
   CIMSS ADT: 51 KTS AT 271730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TC 15P (JUDY) IS PRIMED AND READY TO RAPIDLY
INTENSIFY, THE ONLY INGREDIENT STILL NEEDED IS FOR THE LLC TO
UNDERGO AXISYMMETRIZATION UNDER THE CONVECTION. AS DISCUSSED
ABOVE, THERE ARE SIGNS IN THE SATELLITE DATA SUGGESTING THIS
PROCESS HAS ALREADY BEGUN. TC 15P IS SLOWING AS IT NEARS THE RIDGE
AXIS AND IS FORECAST TO REACH THE RIDGE AXIS NEAR TAU 24. IT JUST
SO HAPPENS THAT THE SYSTEM IS SLOWING AS IT IS MOVING OVER A POOL
OF VERY WARM WATER WITH HIGH OHC VALUES APPROACHING 170 KJ PER CM2.
AS IT CONTINUES TO TRACK TOWARDS PORT VILA, VANUATU, TC 15P IS
FORECAST TO RAPIDLY INTENSIFY, REACHING A PEAK OF AT LEAST 90 KNOTS,
AND POTENTIALLY HIGHER, BY TAU 36. UNFORTUNATELY FOR TC JUDY,
CONDITIONS RAPIDLY DETERIORATE IMMEDIATELY AFTER REACHING PEAK
INTENSITY. BY TAU 48, SOUTHWESTERLY SHEAR IS EXPECTED TO INCREASE
DRAMATICALLY DUE TO THE PASSAGE OF A MID-LATITUDE TROUGH TO THE
SOUTH. THE PASSAGE OF THE TROUGH WILL ALSO INTRODUCE AN INFLUX OF
VERY DRY MID-LEVEL AIR OVER TOP OF THE LOW-LEVEL CORE OF THE
SYSTEM, ESPECIALLY AFTER TAU 60. THE COMBINATION OF THESE FACTORS,
ALONG WITH A TRANSIT OVER STEADILY COOLING SSTS, WILL RESULT IN
STEADY WEAKENING AFTER TAU 48. THE SYSTEM WILL BEGIN SUBTROPICAL
TRANSITION (STT) BETWEEN TAU 60 AND TAU 72, AND IS EXPECTED TO
TRANSITION TO A STORM-FORCE SUBTROPICAL LOW NO LATER THAN TAU 96. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
GOOD AGREEMENT, WITH A PEAK SPREAD AT TAU 48 OF JUST 135NM,
NARROWING TO 120NM BY TAU 96. ALONG TRACK SPREAD INCREASES MODESTLY
TOWARDS THE END OF THE FORECAST PERIOD, AS IS EXPECTED WITH AN
ACCELERATING SYSTEM UNDERGOING STT. THE JTWC FORECAST REMAINS
CONSISTENT WITH THE PREVIOUS FORECAST, AND SLIDES CLOSE TO THE GFS
AND ECMWF SOLUTIONS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE AGREES
ON THE FACT THAT TC 15P WILL INTENSIFY BUT SHOWS A LARGE AMOUNT OF
DISAGREEMENT ON THE PACE AND PEAK. SOMEWHAT SURPRISINGLY, BOTH
VERSIONS OF COAMPS-TC ARE VERY BEARISH ON TC 15P AND FORECAST
LITTLE IN THE WAY OF INTENSIFICATION, WITH A PEAK OF JUST 65 KNOTS.
THE HWRF, AND DECAY-SHIPS (BOTH VERSIONS) ON THE OTHER HAND ARE
VERY BULLISH, PEAKING THE SYSTEM BETWEEN 90-95 KNOTS. ADDITIONALLY,
THE RIPA, RIDE, FRIA AND RI25 TO RI45 RAPID INTENSIFICATION (RI)
AIDS ARE ALL TRIGGERED ON THIS RUN. THE JTWC FORECAST TRACKS THE
MEDIAN OF THE RI GUIDANCE TO A PEAK NEAR THE HWRF SOLUTION WITH
MEDIUM CONFIDENCE. IT REMAINS POSSIBLE THAT IF THE SYSTEM CAN
AXISYMMETRIZE QUICKLY, WHILE REMAINING OVER THE HIGH OHC POOL, IT
COULD UNDERGO RI AT AN EVEN FASTER PACE THAN THE GUIDANCE SUGGESTS
AND REACH A HIGHER PEAK INTENSITY. 

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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