Tropical Cyclone Activity: Indian Ocean (Update 2)

S Indian Ocean: Storm Alert issued at 31 Dec, 2012 18:00 GMT

Tropical Storm SEVEN (07S) currently located near 11.9 S 56.4 E is forecast to strike land to the following likelihood(s) at the given lead time(s):

Yellow Alert Country(s) or Province(s)
    Reunion
        probability for CAT 1 or above is 10% in about 72 hours
        probability for TS is 35% in about 72 hours
Yellow Alert City(s) and Town(s)
    St Pierre (21.3 S, 55.5 E)
        probability for CAT 1 or above is 10% in about 72 hours
        probability for TS is 35% in about 72 hours

Note that
    Yellow Alert (Elevated) is CAT 1 or above to between 10% and 30% probability, or TS to above 50% probability.
    CAT 1 means Tropical Cyclone strength winds of at least 74 mph, 119 km/h or 64 knots 1-min sustained.
    TS means Tropical Storm strength winds of at least 39 mph, 63 km/h or 34 knots 1-min sustained.

REMARKS:
312100Z POSITION NEAR 12.2S 56.1E.
TROPICAL CYCLONE (TC) 07S, LOCATED APPROXIMATELY 565 NM NORTH OF LA 
REUNION, HAS TRACKED WEST-SOUTHWESTWARD AT 13 KNOTS OVER THE PAST 
SIX HOURS. ANIMATED MULTISPECTRAL AND INFRARED IMAGERY SHOW DEEP 
CONVECTION BUILDING ALONG THE NORTHWESTERN QUADRANT OF AN IMPROVING 
LOW LEVEL CIRCULATION CENTER (LLCC) OVER THE PAST 12 HOURS. AN OLDER 
310728Z OSCAT PASS INDICATED WINDS WERE NEARLY 30 KNOTS, AND WITH 
RECENT DVORAK ESTIMATES OF 35 KNOTS FROM PGTW, THERE IS GOOD 
EVIDENCE THE LLCC HAS BEEN STEADILY IMPROVING. A 311652Z TRMM 37H 
PASS SUPPORTS THE IMPROVING ORGANIZATION, WITH MULTIPLE FEEDER BANDS 
ALONG THE SOUTHERN HALF OF THE CIRCULATION. UPPER LEVEL ANALYSIS 
INDICATES A POINT SOURCE ANTICYCLONE IS DEVELOPING OVER THE LLCC, 
AND IS PROVIDING AMPLE RADIAL OUTFLOW AND CREATING A LOW VERTICAL 
WIND SHEAR (VWS) ENVIRONMENT (10 KNOTS). SEA SURFACE TEMPERATURES 
(SSTS) ARE FAVORABLE (29-30 DEGREES CELSIUS) FOR THE SUPPORT OF THE 
SYSTEM AS IT CONTINUES TO INTENSIFY THROUGH TAU 72. BASED ON THE 
FAVORABLE UPPER LEVEL SUPPORT AND GOOD SURFACE CONDITIONS THE 
INTENSITY FORECAST HAS BEEN BROUGHT UP TO 110 KNOTS BY TAU 72, WITH 
THE POSSIBILITY OF RAPID INTENSIFICATION IN THIS FAVORABLE 
ENVIRONMENT. SSTS WILL EVENTUALLY DECREASE, BECOMING UNFAVORABLE FOR 
FURTHER INTENSIFICATION, AS THE LLCC MOVES SOUTH OF 25 DEGREES 
SOUTH, APPROXIMATELY AROUND TAU 84. BY TAU 96 VWS IS EXPECTED TO 
INCREASE TO HIGH LEVELS (30 KNOTS) AND COMBINED WITH THE DECREASING 
SSTS, WILL LEAD TO A RAPID WEAKENING OF THE SYSTEM BY TAU 120. THIS 
FORECAST IS ON THE HIGH SIDE OF AVAILABLE INTENSITY GUIDANCE. MODEL 
GUIDANCE IS IN FAIR AGREEMENT WITH THE TRACK AS A SHIFTING 
SUBTROPICAL RIDGE BRINGS THE SYSTEM SOUTH AND A MID-LATITUDE DEEP 
TROUGH CAPTURES THE LLCC BY TAU 120 TRACKING IT TO THE SOUTHEAST. 
THIS WARNING SUPERSEDES AND CANCELS REF A, JOINT TYPHOON WRNCEN 
PEARL HARBOR HI 302351Z DEC 12 TROPICAL CYCLONE FORMATION ALERT 
(WTXS21 PGTW 310000) MAXIMUM SIGNIFICANT WAVE HEIGHT AT 311800Z IS 
20 FEET.

- JTWC/TropicalStormRisk.com/Eumetsat