Tropical Storm Activity: South Indian Ocean (14 January 2013)

Update: Tropical Cyclone 09S (Emang) Issued at 13/2100Z

132100Z POSITION NEAR 11.8S 80.0E.
TROPICAL CYCLONE (TC) 09S (EMANG), LOCATED APPROXIMATELY 525 NM EAST-
SOUTHEAST OF DIEGO GARCIA, HAS TRACKED WESTWARD AT 05 KNOTS OVER THE 
PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY DEPICTS A 
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH A RECENT 
FLARE OF CONVECTION OVER THE NORTHWEST QUADRANT OF THE LLCC. THE 
INITIAL POSITION BASED ON THE IR IMAGERY AND EXTRAPOLATION FROM A 
131545Z ASCAT PASS WITH FAIR CONFIDENCE. THE INITIAL INTENSITY 
REMAINS ASSESSED AT 35 KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF 
35 KNOTS AND IS CONSISTENT WITH STORM STRUCTURE AS ORGANIZATION HAS 
NOT IMPROVED OVER THE PAST 12 HOURS. UPPER LEVEL ANALYSIS REVEALS TC 
09S IS LOCATED WITHIN A MARGINAL ENVIRONMENT WITH POOR OUTFLOW AND 
MODERATE (10-20 KNOTS) VERTICAL WIND SHEAR. TC 09S REMAINS WITHIN A 
WEAK STEERING ENVIRONMENT BUT HAS PICKED UP SPEED OVER THE LAST SIX 
HOURS TRACKING WESTWARD UNDER THE INFLUENCE OF A BUILDING 
SUBTROPICAL RIDGE (STR) TO THE SOUTH. TC 09S IS EXPECTED TO SLOWLY 
TRACK SOUTHWESTWARD BY TAU 12 ALONG THE NORTHERN PERIPHERY OF THIS 
BUILDING STR. AFTER TAU 48, THE SYSTEM SHOULD TRACK MORE WEST-
SOUTHWESTWARD AS THE STEERING STR RESPONDS TO DEEP MID-LATITUDE 
TROUGH. TC 09S IS EXPECTED TO INTENSIFY SLOWLY TO A PEAK INTENSITY 
OF 65 KNOTS BY TAU 120 UNDER THE MODERATELY FAVORABLE ENVIRONMENTAL 
CONDITIONS THROUGHOUT THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE IS 
IN FAIR AGREEMENT WITH CONTINUED DIFFERENCES IN TRACK SPEED, AS THE 
EUROPEAN MODELS ARE SHOWING A SLOWER TRACK WESTWARD. LOW CONFIDENCE 
REMAINS IN THE JTWC FORECAST TRACK DUE TO THE DIFFERENCES IN TRACK 
SPEEDS IN THE MODELS AND THE PAST ERRATIC MOTION, BUT IS IMPROVING 
BASED ON THE RECENT INCREASE IN MOTION. MAXIMUM SIGNIFICANT WAVE 
HEIGHT AT 131800Z IS 13 FEET.

- JRWC + Eumetsat