Current Southern Hemisphere Tropical Systems: Tropical Cyclone 13S (Thirteen)

280300Z POSITION NEAR 13.2S 59.4E.
TROPICAL CYCLONE (TC) 13S (THIRTEEN) LOCATED APPROXIMATELY 550 NM 
NORTH-NORTHEAST OF LA REUNION, HAS TRACKED WESTWARD AT 11 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY 
CONTINUES TO DEPICT A PARTIALLY-EXPOSED, LOW-LEVEL CIRCULATION 
CENTER (LLCC) LOCATED ALONG THE SOUTHWEST EDGE OF A LARGE AREA OF 
DEEP CONVECTION. UPPER-LEVEL ANALYSIS INDICATES THAT THE ENVIRONMENT 
HAS IMPROVED OVER THE PAST 12 HOURS WITH DECREASING SOUTHERLY 
VERTICAL WIND SHEAR (VWS) OF ABOUT 15 KNOTS, GOOD EQUATORWARD 
OUTFLOW AND GOOD POLEWARD OUTFLOW INTO AN UPPER LOW NEAR 20S 78E. 
THIS HAS LED TO A BETTER ORGANIZED LLCC AS EVIDENT IN A 272337Z SSMI 
IMAGE, WHICH SHOWS IMPROVED DEEP CONVECTIVE BANDING OVER THE EASTERN 
SEMI-CIRCLE AND TIGHTLY-CURVED SHALLOW BANDING OVER THE WESTERN SEMI-
CIRCLE. THERE IS INCREASED CONFIDENCE IN THE INITIAL POSITION BASED 
ON THE WELL-DEFINED LLCC. THE INITIAL INTENSITY IS ASSESSED AT 35 
KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF 35 KNOTS FROM BOTH PGTW 
AND KNES. TC 13S IS FORECAST TO TRACK WESTWARD UNDER THE STEERING 
INFLUENCE OF THE DEEP SUBTROPICAL RIDGE (STR) THROUGH TAU 48 BUT 
WILL THEN TURN SOUTHWARD AND TRACK ALONG THE WESTERN PERIPHERY OF 
THE STR, WHICH IS FORECAST TO RE-ORIENT NORTH-SOUTH AS A DEEP 
MIDLATITUDE TROUGH PROPAGATES TOWARD MADAGASCAR. DUE TO THE 
IMPROVING CONDITIONS, TC 13S IS EXPECTED TO INTENSIFY THROUGH THE 
PERIOD TO A PEAK INTENSITY OF 75 KNOTS BY TAU 96. DYNAMIC MODEL 
GUIDANCE IS IN FAIR AGREEMENT ALTHOUGH THERE ARE SIGNIFICANT 
DIFFERENCES IN THE EXACT TRACK AND TIMING OF THE RE-CURVATURE. THE 
JTWC FORECAST FAVORS THE MULTI-MODEL CONSENSUS AND ECMWF. OVERALL, 
THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK. MAXIMUM 
SIGNIFICANT WAVE HEIGHT AT 280000Z IS 14 FEET.

- JTWC + Eumetsat