1999–2000 South-West Indian Ocean cyclone season
The 1999–2000 South-West Indian Ocean tropical cyclone season was the first on record in which two storms – Leon–Eline and Hudah – struck Mozambique at tropical cyclone intensity, or with maximum sustained winds of at least 120 km/h (75 mph). The most notable storm of the season was Eline, which was the longest-lasting storm on record in the basin. It lasted for 29 days while traversing the southern Indian Ocean, making the strongest landfall in decades along eastern Madagascar in late February. The storm was the first in a series of three storms that struck the country in early 2000, along with Gloria in March and Hudah in April. Collectively, the three storms killed at least 316 people. The season started on November 1, 1999, and ended for most of the basin on April 30, 2000; for Mauritius and the Seychelles, the season continued until May 15. These dates conventionally delimit the period of each year when most tropical cyclones form in the basin;
1999–2000 South Pacific cyclone season
As Leo was developing, a new disturbance formed south of Apia in Western Samoa. The first gale warning was issued on 7 March as it moved closer to northern Tonga. Wind warnings were issued for some islands in Tonga including Vavau, Haapai and Tongatapu. The storm rapidly developed on 8 March at 0600 UTC, and was named Tropical Cyclone Mona six hours later, while located 75 km (45 mi) west of Haapai and moving slowly southward. A storm warning was put for the whole Tongatapu Group on the 8th. An eye developed on 9 March, and Mona was upgraded to hurricane intensity at 0600 UTC, located 55 km (35 mi) west of Tongatapu. Mona moved south-southeastward and accelerated. It reached an intensity of on 10 March, 370 km (230 mi) southeast of Tongatapu. NPMOC's 1-min winds were estimated at . Minimum pressure of Mona was 965 mbar. It began to weaken rapidly, as it sped off southwards, and became extratropical on 11 March at 1200 UTC.