The southwest Indian Ocean basin consists of the area of the Indian Ocean south of the equator and west of 90°E longitude. This area is warned by the designated RSMC in La Réunion, a French island east of Madagascar. Based on data between the 1981/82 to 2010/11 seasons, this basin on average has 9.3 tropical storm-strength cyclones (North American definition of greater than 17 m s-1 1-minute average sustained wind) and 5.0 severe tropical cyclones (hurricane/typhoon definition of greater than 33 m s-1 1-minute average sustained wind) per year (Hurricane Research Center, "Frequently Asked Questions"). The areas that suffer the most from tropical cyclone impacts in this basin are Mauritius, La Réunion, Madagascar, Mayotte, Comoros, and Mozambique. Occasionally, parts of Tanzania, Swaziland, and South Africa can be affected as well as inland countries of Africa such as Malawi and Zimbabwe.
Very Intense Tropical Cyclone Gafilo (defined as such by RSMC La Réunion) is the strongest recorded tropical cyclone in the southwest Indian Ocean basin. Gafilo formed in the south central Indian Ocean area on 02 March 2004. Over the next few days, Gafilo strengthened steadily while moving southwest. Gafilo deepened to 895
hPa central pressure off the coast of Madagascar while its winds strengthened to a 1-minute sustained average of 140
knots(160 MPH) which correlates to a category five hurricane in the north Atlantic. Shortly after reaching this maximum strength on 07 March, Gafilo made landfall near Antahala on the northeast coast of Madagascar (United States, Annual Tropical Cyclone Report-2004 256). After Gafilo crossed Madagascar, it entered the Mozambique Channel as a 65 knot cyclone, then
recurved southeastward over southern Madagascar while moving very slowly. Gafilo finally dissipated on 11 March 2004. The impact on Madagascar was catastrophic. The northern coastal areas were devastated by high winds and storm surge, while the country as a whole was decimated by flooding rains as Gafilo’s rains affected the nation for over four days only weeks after being struck by Tropical Cyclone Elita. 172 deaths and 879 injuries were reported, while 214,260 people lost their homes, and roughly 773,000 people were affected (IFRC). In all, Gafilo was one of the worst tropical cyclones to ever strike the impoverished African nation.
Intense Tropical Cyclone Leon-Eline was a very long-lived storm that crossed the entire southern Indian Ocean. The system formed as Tropical Cyclone Leon south of Java in the Perth Tropical Cyclone Warning Center’s region of responsibility on 04 February 2000. As Leon moved towards the southwest, it intensified to 70 knots before
wind shear began to weaken the cyclone. After Leon weakened, it began to move more westerly. Leon crossed the 90°E longitude meridian into the southwest Indian Ocean on 08 February 2000 where it was renamed Eline by RSMC La Réunion. Eline stayed fairly weak until 12 February when conditions became more favorable. As Eline approached Madagascar, it underwent significant strengthening to a peak of 90 knots (United States, Annual Tropical Cyclone Report-2000). A slightly weaker Eline then made landfall just north of Mahanoro, Madagascar on 17 February. Five people were killed and thousands were left homeless on Madagascar by Eline’s impact… unfortunately, the worst was yet to come. Eline emerged over the Mozambique Channel on 19 February greatly weakened, though still in a very favorable environment for strengthening. By 22 February, Eline had strengthened to its peak of 115 knots, the equivalent of a category four hurricane in the north Atlantic. Fortunately, Eline weakened to 85 knots before making landfall near Beira, Mozambique, though that was not enough to prevent extreme damage from occurring. Mozambique already had tremendous amounts of flooding and damage occurring across the country from previous torrential rains and cyclones when Eline struck. Eline directly killed 200 people and left 500,000 people homeless in Mozambique. An additional 700 people were killed by continued flooding from Eline and a later tropical cyclone, Gloria, in Mozambique, Zimbabwe, and South Africa. Eline finally dissipated over Zimbabwe on 23 February 2000.
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