060300Z POSITION NEAR 20.5S 59.7E.
TROPICAL CYCLONE 13S (EDILSON), LOCATED APPROXIMATELY 266 NM EAST OF
ST DENIS, LA REUNION, HAS TRACKED SOUTHWARD AT 09 KNOTS OVER THE PAST
SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS A STEADY
INCREASE IN DEEP CONVECTIVE BANDING ALONG THE SOUTHWESTERN QUADRANT
WRAPPING INTO THE NORTHERN HALF OF THE SYSTEM. A SERIES OF UPPER
LEVEL TROUGHS TO THE EAST AND WEST OF TC 13S HAVE AMPLIFIED THE
POLEWARD OUTFLOW CHANNEL IN THE PAST 12 HOURS, HELPING TO VENT THE
LOW LEVEL CIRCULATION CENTER. CURRENT MODEL GUIDANCE INDICATES
THE SYSTEM IS TRACKING ALONG THE NORTHWESTERN QUADRANT OF A LOW- TO
MID-LEVEL RIDGE ANCHORED TO THE SOUTHEAST OF TC 13S. A REFLECTION OF
THE TROUGH ON THE WESTERN SIDE OF THE SYSTEM IS ENHANCING THE
GRADIENT STEERING FLOW, ACCELERATING TC 13S TO THE SOUTH-SOUTHWEST.
THE MAXIMUM INTENSITY HAS BEEN ADJUSTED TO 60 KNOTS AT TAU 36 BASED
ON INCREASED UPPER LEVEL VENTING SUPPORT FROM THE AFOREMENTIONED
TROUGH. BEYOND TAU 36, THE CURRENTLY FAVORABLE SEA SURFACE TEMPER-
ATURES WILL BEGIN TO DECREASE, AND AS THE UPPER LEVEL TROUGH TRACKS
EASTWARD, THE OUTFLOW WILL BEGIN TO BE DEGRADED. ADDITIONALLY, THE
TROUGH WILL CAUSE VERTICAL WIND SHEAR TO INCREASE, LEADING TO A
WEAKENING TREND. BY TAU 96 INTERACTION WITH THE MID-LATITUDE WESTER-
LIES WILL LEAD TO THE START OF AN EXTRA-TROPICAL TRANSITION. INTER-
ACTION OF THE WESTERN TROUGH AND THE RIDGE WILL CAUSE TC 13S TO
SHIFT TO A SOUTHEASTERN TRACK, ACCELERATING IN THE MID-LATITUDE
FLOW. BY TAU 120 THE SYSTEM IS EXPECTED TO BE FULLY TRANSITIONED TO
AN EXTRA-TROPICAL LOW. CONTINUED GOOD AGREEMENT AMONGST THE MODEL
GUIDANCE LEADS TO HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.
MAXIMUM SIGNIFICANT WAVE HEIGHT AT 060000Z IS 14 FEET.
- JTWC
