WDXS31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02S (BHEKI) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.4S 69.3E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 701 NM EAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS TC 02S HANGING
IN STRONG, MAINTAINING A CLOUD-FILLED EYE THROUGHOUT MOST OF THE
PAST SIX HOURS, WITH DEEP CONVECTION STILL FIRING OFF IN THE
SURROUNDING EYEWALL. A 180448Z NOAA-19 MHS 89GHZ MICROWAVE IMAGE
REVEALED THAT THE VORTEX IS ALREADY STARTING TO DECOUPLE WITH THE
UPPER-LEVEL CENTER (OR EYE) DISPLACED EAST OF THE LOW LEVEL
CIRCULATION CENTER (LLCC) BY ALMOST A FULL DEGREE OF LONGITUDE.
THIS SUGGESTS THAT THE CIMSS ESTIMATED SHEAR OF 12 KNOTS IS TOO LOW
AND THE ACTUAL SHEAR MAY BE CLOSER TO THE GFS AND ECMWF MODEL
INDICATED VALUE CLOSER TO 20-25 KNOTS. REGARDLESS, THE SYSTEM HAS
ALREADY STARTED THE DECOUPLING PROCESS. THE INITIAL POSITION IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE ANIMATED MSI AND
ANALYSIS OF THE LOW-RESOLUTION MICROWAVE IMAGERY. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, ROUGHLY IN THE
MIDPOINT OF THE AGENCY CURRENT INTENSITY ESTIMATES RANGING FROM
T5.0 TO T6.0 AND CLOSE TO THE CIMSS DMINT AND DPRINT ESTIMATES.
ENVIRONMENT IS STARTING TO DETERIORATE RAPIDLY, WITH INCREASING
SHEAR AND MARGINAL SSTS OFFSETTING STRONG POLEWARD OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: SAR DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T5.5 - 102 KTS
   FMEE: T5.5 - 102 KTS
   FIMP: T5.0 - 90 KTS
   CIMSS SATCON: 77 KTS AT 180630Z
   CIMSS ADT: 84 KTS AT 180600Z
   CIMSS AIDT: 81 KTS AT 180500Z
   CIMSS D-MINT: 94 KTS AT 180137Z
   CIMSS D-PRINT: 90 KTS AT 180630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 AT
A RELATIVELY SLOW PACE FOR THE NEXT 12 HOURS AS IT SITS IN A WEAK
STEERING PATTERN, CAUGHT BETWEEN THE STRONG STR TO THE EAST,
ANOTHER RIDGE FAR TO THE WEST, AND A PASSING TROUGH TO THE SOUTH.
THE TRACK SHIFTS A BIT MORE WEST-SOUTHWESTWARD AFTER TAU 12, AS THE
VORTEX RAPIDLY DECOUPLES AND THE LOWER-LEVEL FLOW
EAST-SOUTHEASTERLIES ASSOCIATED WITH THE MASCARENE HIGH TAKES OVER
AS THE PRIMARY STEERING MECHANISM. THE SYSTEM WILL CONTINUE
TRACKING ALONG THE NORTHERN SIDE OF THE MASCARENE HIGH FOR THE
REMAINDER OF THE FORECAST PERIOD, PASSING NORTH OF PORT MATHURIN
AND VERY CLOSE TO BOTH MAURITIUS AND LA REUNION IN THE LATER PORTION
OF THE FORECAST. SHEAR IS EXPECTED TO STEADILY INCREASE OVER THE
NEXT DAY AND WILL BE ACCOMPANIED BY VERY DRY MID-LEVEL AIR PUSHING
IN FROM THE WEST. THE WILL WEAKEN SLOWLY AT FIRST, FOLLOWED BY MORE
RAPID WEAKENING THROUGH TAU 36. THE REMNANT VORTEX WILL THEN VERY
SLOWLY WIND DOWN THROUGH THE REMAINDER OF THE FORECAST, ULTIMATELY
DISSIPATING BY TAU 96, AND POTENTIALLY AS EARLY AS TAU 72. THE
SYSTEM IS NOT CURRENTLY EXPECTED TO TRANSITION TO A SUBTROPICAL
LOW, BUT IF IT TRACKS FURTHER SOUTH THAN CURRENTLY FORECAST, IT
WILL LIKELY MAKE THE TRANSITION AFTER TAU 48. 

MODEL DISCUSSION: TRACK GUIDANCE CONTINUES TO SHOW A MODERATE
AMOUNT OF UNCERTAINTY, BUT HAS COME INTO BETTER AGREEMENT OVER THE
PAST 24 HOURS, WITH THE BULK OF THE GUIDANCE CONVERGING ON A TRACK
CLOSER TO MAURITIUS AND LA REUNION. THE CONSENSUS MEAN IS CENTERED
ON THE ISLANDS, WITH GFS, GEFS AND UKMET ENSEMBLE TO THE NORTH AND
THE ECMWF, ECEPS, AND NAVGEM TO THE SOUTH. THE JTWC FORECAST RIDES
THE SOUTHERN EDGE OF THE NORTHERN GROUP AND JUST SOUTH OF THE
CONSENSUS MEAN THROUGH THE ENTIRE FORECAST. CONFIDENCE IS MEDIUM TO
TAU 72, THEN LOW. INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT THE
SYSTEM WILL STEADILY WEAKEN THROUGH THE FORECAST PERIOD, WITH HWRF
AND COAMPS-TC SUGGESTING DISSIPATION AS EARLY AS TAU 48. THE JTWC
FORECAST IS A BIT MORE CONSERVATIVE AND DELAYS DISSIPATION DUE TO
THE CLIMATOLOGICAL TREND OF SYSTEMS IN THIS BASIN WHICH ONLY SLOWLY
SPIN-DOWN. 

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