2000–01 South-West Indian Ocean cyclone season

The 2000–01 South-West Indian Ocean cyclone season was a fairly quiet season with only five named storms, although there was an additional unnamed tropical storm and two subtropical cyclones with gale-force winds. It started early, with a tropical disturbance forming on August 1 – the first day of the cyclone year. However, the first named storm, Ando, was not named until January 2, which at the time was the 4th latest on record. Ando would become the most intense cyclone of the year, reaching peak winds of according to the Météo-France office (MFR) on Réunion, the official Regional Specialized Meteorological Center for the basin. The agency tracked storms south of the equator and west of 90°E to the east coast of Africa.

In addition to being the strongest storm, Cyclone Ando was one of two deadly storms during the season. It passed about west of Réunion, producing of rainfall in the mountainous peaks. The rains led to flooding that killed two people. Ando was one of three storms to attain tropical cyclone status – winds of at least – in the month of January. The others were Bindu, which alternated its trajectory several times over open waters, and Charly, which rapidly weakened after encountering hostile wind shear. The next storm to form was Tropical Cyclone Dera, which intensified near Mozambique in early March and killed two people there due to flooding rains. It later moved southward through the Mozambique Channel, maintaining its intensity unusually far to the south before becoming extratropical. There was a month of inactivity in March, including three weeks in which there were no storms worldwide, the first such instance. Subsequently, two storms formed in early April; one was a small, unnamed tropical storm, and the other was Severe Tropical Storm Evariste, which brought light rainfall to two islands. The season ended with an unusual subtropical storm forming rapidly in the southern Mozambique Channel on June 19, the only such storm to form in that body of water in the month. It became the strongest storm on record for so late in the season, although it weakened without affecting land, dissipating on June 24. __TOC__

Season summary

During the season, the Météo-France office (MFR) on Réunion island issued warnings in tropical cyclones within the basin. The agency estimated intensity through the Dvorak technique, and warned on tropical cyclones in the region from the coast of Africa to 90° E, south of the equator to 30° S. At the time, the cyclone year was from August 1 to July 31 of the subsequent year. The Joint Typhoon Warning Center (JTWC), which is a joint United States Navy – United States Air Force task force, also issued tropical cyclone warnings for the southwestern Indian Ocean in an unofficial capacity.

Aside from a tropical disturbance in August, the season began later than usual, the fourth consecutive season to do so. At the time it had the 4th latest start on record for the first named storm. Only about 20% of seasons have their first storm form after the middle of December, and the first named storm of this season, Ando, did not become a tropical storm until early January. However, January was active with three tropical cyclones, two of which became intense tropical cyclones, due to the active phase of the Madden–Julian oscillation (MJO). February returned to a period of inactivity, and generally there was minimal convection across the basin due to unusually dry air. This was spread by a powerful and persistent ridge that extended eastward from Madagascar, as well as an inactive phase of the MJO. Drought conditions occurred on Réunion due to the lack of rainfall. After three weeks of no tropical cyclones developing worldwide, an event unseen since 1995, the tropics became active again in early April.

In contrast with the busy preceding season, this season had much lower activity than usual, with only 36 days in which there was a tropical storm or cyclone active; this was 17 less than normal. However, the number of days with a tropical cyclone was slightly above normal at 15. In general, the southern hemisphere as a whole had the least active season since 1954. There were only five named storms, only the fifth such time since the beginning of the satellite era in 1967. As most storms formed toward the eastern periphery of the basin, damage was much less than the preceding year.

Systems Tropical Depression 01

On August 1, in the middle of the southern hemisphere's winter, an area of convection persisted in the northeastern portion of the basin about northeast of Diego Garcia. At that time, an associated circulation was exposed to the east of the thunderstorms. At 06:00 UTC that day, the MFR initiated advisories on Tropical Disturbance 1. After the system organized further, the JTWC also began tracking the system as Tropical Cyclone 01S, estimating winds of . With a ridge to the south, the system tracked generally westward, briefly becoming a tropical depression on August 1. An approaching trough weakened the ridge, allowing the depression to turn southwestward. Located in an area of moderate wind shear, the system failed to intensify further, and it dissipated on August 3.

Tropical Depression 02

An area of convection formed on November 9 to the east of Diego Garcia, possibly the result of the MJO. A circulation was evident by November 11, and the following day it developed into Tropical Disturbance 2 about southeast of Diego Garcia. Also on November 12, the JTWC classified the system as Tropical Cyclone 02S. It moved to the southwest, but looped back to the east on November 13, during which time the MFR upgraded it to tropical depression status. Later that day, the agency ceased issuing advisories, but the system reorganized on November 14. On November 17, it turned back to the southwest, but the MFR discontinued advisories on the next day.

Intense Tropical Cyclone Ando

The beginnings of Ando can be traced to a circulation within the Intertropical Convergence Zone (ITCZ) about south-west of Diego Garcia, which became evident on satellite imagery on December 30. Associated convection, or thunderstorms, gradually organized into a central dense overcast, and the system became Tropical Disturbance 3 at 06:00 UTC on December 31. The upper-level environment generally favored further development, but the system failed to develop more initially due to some easterly wind shear. A large ridge to the south steered the nascent disturbance to the west-southwest. After the shear subsided, the system intensified into a moderate tropical storm on January 2, given the name "Ando" by the Mauritius Meteorological Service. Also on that day, the JTWC began issuing advisories on the storm as Tropical Cyclone 04S, and around that time, Ando was passing about east-southeast of Agaléga island.

Ando rapidly intensified after forming and attained tropical cyclone status early on January 4, developing an eye in the center of the thunderstorms and outflow to the east. A tropical low over the southern Mozambique Channel weakened the ridge, causing Ando to turn more to the southwest. Late on January 4, the storm intensified further into an intense tropical cyclone, and early the next day passed about northeast of Tromelin Island. According to the JTWC, however, Ando attained peak 1 minute winds of late on January 5. In contrast, the MFR assessed Ando as weakening due to the becoming larger and less defined, while still maintaining a small cloud diameter of about . However, the eye re-organized, and Ando attained peak 10 minute winds of on January 6, with a eye at the time. Continuing around the ridge, the cyclone passed about west of Réunion that day before starting to weaken due to increased wind shear. On January 8, Ando weakened below tropical cyclone status, and the convection increasingly separated from the circulation while turning to the southeast. On January 10, the storm became extratropical, although the remnants turned back to the northwest due to the ridge, dissipating on January 13.

As a developing storm, Ando produced some heavy rain between December 30 and January 2 over Seychelles. Swaziland also reported that Ando drew moisture from the continent, aggravating a persistent dry spell. While near Agaléga island, Ando dropped of rainfall, compared to a January average precipitation there of . On Tromelin Island, gusts peaked at and rainfall reached . Passing north of Réunion, Ando produced gusts of along the coast, but was recorded at Plaine des Cafres in the mountainous peaks. Most parts of the island did not receive much rain, with the exception of mountainous peaks due to orographic lift, particularly after the center passed to the west. Pas de Bellecombe at an elevation of reported over 48 hours. The rains caused flooding and some landslides, which washed away one house and killed two people. Ando also damaged crops and killed several livestock. The highest wave recorded was in La Possession. High waves injured several people, several of whom required rescue from lifeguards.

Tropical Cyclone Bindu

On January 2, an area of convection persisted in the eastern portion of the ITCZ in the Australian basin, located northwest of Cocos Island, or about southwest of Sumatra. With a ridge to the south, the system moved generally westward. A nearby ship confirmed that a circulation formed, and on January 3, it crossed 90°E into the south-west Indian Ocean as a tropical disturbance. With easterly wind shear, the system initially remained weak, but convection increased and organized on January 5. On the next day, the disturbance intensified into a tropical depression, although the circulation was still exposed from the thunderstorms at that time. After turning to the southwest, wind shear decreased, and the depression became Moderate Tropical Storm Bindu on January 7. On the same day, the JTWC also initiated advisories as Tropical Cyclone 05S. Moving around the ridge to the south, Bindu slowly intensified, developing outflow and improved rainbands. Early on January 9, the MFR upgraded the storm to tropical cyclone status as an eye in diameter formed. The next day, Bindu weakened due to increased wind shear, causing the circulation to be exposed from the convection and for the cyclone to be downgraded into a severe tropical storm.

The building ridge caused the storm to slow and turn back to the west. After the formerly hostile shear relaxed, Bindu became a tropical cyclone again on January 11, redeveloping an eye. On the next day, the MFR estimated peak 10 minute winds of , while the JTWC estimated maximum 1 minute winds of . By that time, the cyclone had turned back to the south-southwest. Drier air and wind shear resulted in weakening, and Bindu was downgraded to a severe tropical storm on January 14. At 18:00 UTC the next day, the storm passed about southeast of Rodrigues island, by which time the circulation was exposed north of the dwindling convection. The MFR downgraded Bindu to tropical depression status on January 16. An approaching trough turned the system to the south on the next day, and Bindu became extratropical late on January 17. The remnants turned sharply eastward due to a ridge, later looping back to the west on January 20. Another trough turned the storm southward on January 21 and absorbed the circulation the next day.

Intense Tropical Cyclone Charly