WDXS31 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02S (BHEKI) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0S 70.7E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 544 NM SOUTH OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RATHER
IMPRESSIVE TROPICAL CYCLONE, WITH A WELL-DEFINED 22NM EYE WITH A
EYE TEMPERATURE OF 11C. A SERIES OF THREE MHS 89GHZ MICROWAVE
IMAGES BETWEEN 0400Z-0500Z REVEALED A STRONG EYEWALL COMPLETELY
SURROUNDING A MICROWAVE EYE FEATURE, THROUGH THE NORTHEAST PORTION
OF THE EYEWALL REMAINS RELATIVELY WEAK. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE 22NM EYE IN THE MSI AND
AN EXTRAPOLATION OF THE MICROWAVE EYE FEATURE IN THE MICROWAVE
IMAGES NOTED ABOVE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE, HEDGED SLIGHTLY HIGHER THAN THE BULK OF THE AGENCY
DVORAK CURRENT INTENSITY ESTIMATES OF T5.5 IN LIGHT OF THE HIGHER
CIMSS ADT, AIDT AND DPRINT ESTIMATES NOTED ABOVE. ENVIRONMENTAL
CONDITIONS REMAIN FAVORABLE FOR THE TIME BEING, WITH LOW VERTICAL
WIND SHEAR (VWS) AND GOOD POLEWARD OUTFLOW ALOFT. THOUGH SSTS
REMAIN MARGINAL AT 26-27C, THE SYSTEM HAS BEEN ABLE TO STEADILY
INTENSIFY OVER THE PAST DAY.

INITIAL WIND RADII BASIS: SAR DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   DEMS: T5.5 - 102 KTS
   FMEE: T5.5 - 102 KTS
   FIMP: T5.5 - 102 KTS
   CIMSS SATCON: 107 KTS AT 170211Z
   CIMSS ADT: 112 KTS AT 170600Z
   CIMSS AIDT: 110 KTS AT 170630Z
   CIMSS D-PRINT: 108 KTS AT 170630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 02S WILL CONTINUE TO TRACK SOUTHWESTWARD
FOR THE NEXT 12 TO 24 HOURS, ALONG THE WESTERN SIDE OF THE STEERING
RIDGE TO THE EAST. HOWEVER, TRACK SPEEDS ARE EXPECTED TO SLOW DOWN
AS A WEAKNESS IN THE STEERING RIDGE DEVELOPS TO THE SOUTH AND THE 
SYSTEM MOVES INTO A RELATIVELY WEAK STEERING PATTERN. THE PASSING 
TROUGH IS NOT EXPECTED TO BE STRONG ENOUGH TO INDUCE TC 02S TO TRACK 
POLEWARD AND THE PASSAGE OF A SUCCESSION OF TRANSIENT DEEP-LAYER 
ANTICYCLONES TO THE SOUTH WILL STEER TC 02S ONTO A MORE WESTWARD TRACK 
AFTER TAU 24. AFTER TAU 48, THE SYSTEM WILL ACCELERATE TOWARDS THE 
WEST-SOUTHWEST ALONG THE NORTHWEST SIDE OF A BUILDING STR THAT DEVELOPS 
SOUTHEAST OF MAURITIUS. IN TERMS OF INTENSITY, THE SYSTEM HAS LIKELY 
PEAKED IN INTENSITY, BUT A SLIGHT AMOUNT OF FURTHER INTENSIFICATION 
CANNOT BE RULED OUT AS CONDITIONS ARE EXPECTED TO REMAIN FAVORABLE FOR 
ABOUT ANOTHER 12 HOURS. AFTER TAU 12, THE SYSTEM IS EXPECTED TO MOVE 
INTO A REGION OF COOLER SSTS, AND SOUTHWESTERLY SHEAR IS FORECAST TO
INCREASE, LEADING TO A GENERAL WEAKENING PHASE. AFTER TAU 36, THE
SYSTEM WILL BE DECAPITATED BY VERY STRONG WESTERLY SHEAR, WHICH
WILL ALSO USHER IN A WEDGE OF EXTREMELY DRY MID-LEVEL AIR OVER TOP
OF THE SYSTEM, AND THE SYSTEM WILL RAPIDLY WEAKEN UP TO TAU 48.
THEREAFTER THE REMNANT LOW-LEVEL VORTEX WILL SLOWLY DISSIPATE AS IT
TRACKS WEST-SOUTHWESTWARD ALONG THE NORTHERN SIDE OF THE STRONG
LOW- TO MID-LEVEL ANTICYCLONE TO THE SOUTH.  

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT IN THE
SHORT-TERM (THOUGH TAU 24) BUT BEGINS TO DIVERGE SIGNIFICANTLY BY
TAU 36. TWO DISTINCT GROUPS EMERGE BY TAU 48; THE ECMWF, ECMWF
ENSEMBLE AND THE NAVGEM, WHICH TAKE THE SYSTEM MUCH FURTHER SOUTH,
ULTIMATELY TRACKING THE VORTEX VERY NEAR PORT MARUTHIN AND SOUTH OF
MAURITIUS AND LA REUNION. MEANWHILE THE REMAINDER OF THE CONSENSUS
INCLUDING GFS, GEFS, GALWEM, EGRR AND UKMET ENSEMBLE PASS THE
SYSTEM FURTHER NORTH, KEEPING THE VORTEX NORTH OF MAURITIUS AND LA
REUNION. THE JTWC FORECAST LIES ON THE SOUTHERN EDGE OF THE
NORTHERN GROUPING OF MODELS AFTER TAU 24, WITH MEDIUM CONFIDENCE.
INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT THE SYSTEM WILL
RAPIDLY WEAKEN, ESPECIALLY AFTER TAU 24. THE JTWC FORECAST REMAINS
WELL ABOVE THE GUIDANCE THROUGH TAU 24, BUT THEN FOLLOWS THE HWRF
TREND THROUGH THE REMAINDER OF THE FORECAST. 

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