WDXS32 PGTW 310900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12S (ELVIS) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.7S 48.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 722 NM SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 12S (ELVIS) IS CURRENTLY ANALYZED AS A HYBRID
TYPE SYSTEM, WITH CHARACTERISTICS OF BOTH A TROPICAL CYCLONE AND AN
EXTRATROPICAL CYCLONE AND IS CURRENTLY IN THE PROCESS OF
EXTRATROPICAL TRANSITION. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS A FULLY DECOUPLED VORTEX, WITH THE LOW LEVEL
CIRCULATION CENTER (LLCC) NOW FULLY EXPOSED TO THE NORTHWEST OF THE
MID- AND UPPER-LEVEL ROTATION. THE INITIAL POSITION IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC. THE INITIAL
INTENSITY IS ASSESSED WITH HIGH CONFIDENCE, WITH A 310322Z SMOS
PASS REVEALING 35-42 KNOT WINDS AROUND THE MAJORITY OF THE WESTERN
HALF OF THE CIRCULATION. THE ENVIRONMENT IS NOW HIGHLY UNFAVORABLE,
WITH COOL, BORDERLINE COLD SSTS, AND VERY STRONG SHEAR EXCEEDING 35
KNOTS. MODEL-DERIVED PHASE SPACE DIAGRAMS INDICATE THE SYSTEM IS A
SHALLOW, INCREASINGLY ASYMMETRIC WARM-CORE SYSTEM, AT LEAST FOR THE
MOMENT, WHILE MODEL-DERIVED SOUNDINGS INDICATE A VERY DRY AIRMASS
ABOVE ABOUT 700MB.

INITIAL WIND RADII BASIS: SMOS DATA. 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) SOUTH OF LA REUNION. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 35 KTS AT 310600Z
   CIMSS AIDT: 42 KTS AT 310600Z
   CIMSS D-MINT: 35 KTS AT 310252Z
   CIMSS D-PRINT: 33 KTS AT 310600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30+ KTS
   SST: 23-24 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: STRONG THERMAL ADVECTION AND DRY AIR ENTRAINMENT.


ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 12S IS ON RAPIDLY TRANSITIONING TO AN
EXTRATROPICAL CYCLONE AS OF THIS MOMENT. THE SYSTEM IS QUICKLY
ACCELERATING TOWARDS THE SOUTHEAST, ALONG THE TIGHT GRADIENT
BETWEEN THE STR TO THE NORTHEAST AND A DEEP UPPER-LEVEL TROUGH
APPROACHING FROM THE WEST. THE SYSTEM IS ALREADY EXHIBITING
MODERATE LEVELS OF THERMAL ADVECTION AND THE UNDERGOING
FRONTOGENESIS, MARKING THE START OF ETT. TC 12S WILL MOVE UNDER A
STRONG 200MB JET MAX AND BECOME EMBEDDED WITHIN A 500MB TROF WITHIN
THE NEXT 24 HOURS, EVOLVING INTO A GALE-FORCE EXTRATROPICAL LOW AS
IT MOVES DEEPER INTO THE SOUTHERN INDIAN OCEAN. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN VERY STRONG
AGREEMENT, WITH MINIMAL CROSS- OR ALONG-TRACK SPREAD, LENDING HIGH
CONFIDENCE TO THE JTWC FORECAST TRACK. INTENSITY GUIDANCE REMAINS
SOMEWHAT MIXED, WITH BOTH THE NAVGEM AND GFS-BASED SHIPS GUIDANCE
INDICATING RAPID WEAKENING TO JUST 20 KNOTS BY TAU 36. THE
MESOSCALE MODELS ACTUAL DEPICT A SLIGHT INTENSIFICATION DURING THE
SAME TIMEFRAME, LIKELY AS A RESULT OF BAROCLINIC FORCING AS THE
SYSTEM GOES EXTRATROPICAL. THE JTWC FORECAST FOLLOWS THE CONSENSUS
MEAN WITH MEDIUM CONFIDENCE. 

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