WDXS31 PGTW 291500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN) WARNING 
NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.5S 71.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 826 NM EAST-SOUTHEAST OF PORT LOUIS,
MAURITIU
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH MARGINAL POLEWARD
OUTFLOW. A 291125Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS TIGHTLY
WRAPPING LOW LEVEL CLOUD LINES IN ALL QUADRANTS WITH MINIMAL DEEP
CONVECTIVE TOWERS SEQUESTERED SOUTHEAST OF THE LLCC. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI AND SSMIS
IMAGERY. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON FALLING AGENCY DVORAK FINAL T NUMBERS, THOUGH
CURRENT INTENSITIES LAGS BEHIND. FURTHERMORE, A RECENT 290846Z
AMSR2 MICROWAVE RADIOMETER PASS REVEALED A FIELD OF 40-45 KNOT
WINDS POSITIONED WITHIN THE LONE DEEP CONVECTION TO THE SOUTHEAST
OF THE LLCC. THIS DISPARITY BETWEEN FINAL T, CURRENT INTENSITY AND
LONE AMSR2 WIND DATA IS THE PRIMARY REASON FOR MEDIUM CONFIDENCE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE EAST-SOUTHEAST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   FMEE: T3.0 - 45 KTS
   CIMSS SATCON: 48 KTS AT 290836Z
   CIMSS ADT: 41 KTS AT 290915Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR WRAPPING ALMOST COMPLETELY
AROUND THE LLC

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 05S (DARIAN) IS FORECAST TO CONTINUE
SOUTHWESTWARD AS IT TRACKS ALONG THE WESTERN PERIPHERY OF THE STR
ENTRENCHED TO ITS EAST-SOUTHEAST. WITHIN THE COMING HOURS AND
THROUGH TAU 24, 05S WILL BEGIN TO INTERACT WITH THE BAROCLINIC ZONE
AND CONSEQUENTLY 05S WILL PROGRESS THROUGH AND COMPLETE
SUB-TROPICAL TRANSITION (STT). AS THE SYSTEM CONTINUES POLEWARD OF
THE 30TH PARALLEL, DRY AIR ENTRAINMENT AND VERTICAL WIND SHEAR
DRAMATICALLY INCREASE, COUPLED WITH PLUMMETING SEA SURFACE
TEMPERATURES THE SYSTEM INTENSITY BEGINS TO FALL PRECIPITOUSLY. BY
TAU 36, NOW POLEWARD OF THE STR AXIS, 05S WILL INITIATE
EXTRA-TROPICAL TRANSITION (ETT). BY TAU 72 AS TRACK SPEED CONTINUE
TO ACCELERATE AND ALL REMAINING TROPICAL CHARACTERISTICS ARE LOST,
05S WILL COMPLETE ETT AND FINISH ITS RAMPAGE THROUGH THE SOUTHERN
INDIAN OCEAN. THE ALIGNMENT AND PROXIMITY OF A TROUGH TO THE WEST
SHOULD PROVIDE BAROCLINIC ASSISTANCE IN MAINTAINING GALE FORCE
WINDS THROUGHOUT THE TRANSITION.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT THAT 05S
WILL CONTINUE TO ROUND THE STR THROUGH THE FORECAST PERIOD WITH
LESS THAN A 100NM CROSS TRACK DEVIATION WHEN EXCLUDING NAVGEM.
BASED ON THIS THE JTWC FORECAST TRACK IS PLACED WITH HIGH
CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE INDICATES A
CONSISTENT THEME THROUGH TAU 24 WITH ALL MEMBERS REMAINING TIGHTLY
PACKED NEAR 50 KNOTS. AFTER TAU 24 DECAY-SHIPS TAKES A DRAMATIC AND
UNSUPPORTED NOSE-DIVE WHILE THE BULK OF THE GUIDANCE AND THE
MUTI-MODEL CONSENSUS INDICATE GRADUAL WEAKENING, WHICH IS WHERE THE
JTWC FORECAST INTENSITY IS PLACED. BASED ON THESE FACTORS THE JTWC
INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE.

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