1993–94 South-West Indian Ocean cyclone season

The 1993–94 South-West Indian Ocean cyclone season was the most active season in the basin since the start of reliable satellite coverage in 1967, until the record was surpassed 25 years later in the 2018–19 South-West Indian Ocean cyclone season. Activity lasted from mid-November, when Moderate Tropical Storm Alexina formed, until mid-April, when Tropical Cyclone Odille became extratropical. Four tropical cyclones – Daisy, Geralda, Litanne, and Nadia – struck eastern Madagascar, of which Geralda was the costliest and deadliest. With gusts as strong as accompanied by heavy rainfall, Geralda destroyed more than 40,000 homes and left 356,000 people homeless. Geralda killed 231 people and caused more than $10 million in damage. Cyclone Nadia was the second deadliest cyclone, having killed 12 people in northern Madagascar and later severely damaging portions of northeastern Mozambique, killing about 240 people and leaving $20 million in damage in the latter country. In February, Cyclone Hollanda struck Mauritius near peak intensity, causing $135 million in damage and two deaths.

Three storms – Alexina, Bettina, and Cecilia – formed in late 1993, of which Cecilia affected land; it produced heavy rainfall in Réunion while dissipating. Cyclone Daisy was the first storm in 1994, which struck Madagascar twice and affected many areas that were later struck by Geralda. One cyclone – Farah – previously formed in the Australian basin as Tropical Cyclone Pearl before crossing into the south-west Indian Ocean. Tropical Cyclone Ivy threatened Mauritius just days after Hollanda struck, and Intense Tropical Cyclone Litanne in March was the third of the season to hit northeastern Madagascar. The basin is defined as the area west of 90°E and south of the Equator in the Indian Ocean, which includes the waters around Madagascar westward to the east coast of Africa. Tropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in Réunion (MFR), as well as by the Joint Typhoon Warning Center (JTWC).

__TOC__

Seasonal summary

On July 1, 1993, the Météo-France office in Réunion (MFR) became a Regional Specialized Meteorological Center, as designated by the World Meteorological Organization. In the year, MFR tracked tropical cyclones south of the equator from the coast of Africa to 90° E. Due to the high activity during the season, MFR issued twice the number of advisories as in the previous year. Every six hours in the season, the agency issued bulletins when there was a tropical system within the basin. Storms were named by advisory centers in Mauritius and Madagascar.

During the year, there were neutral El Niño Southern Oscillation conditions, and for several months there was a well-established monsoon trough that extended into the Australian basin. The average storm duration was 9 days, although the final storm, Odille, lasted 16 days, a record at the time. The season was the second-most active on record since the start of reliable satellite coverage in 1967. Due to the high number of storms, there were a record number of cyclone days – days in which a tropical cyclone is active – as well as intense tropical cyclone days, with a total of 27 days for the latter. The next seasons to approach either total were the 2001–02 and 2018–19 seasons. MFR had an alphabetically prepared list of names for the season, the last seven of which went unused: Pemma, Ronna, Sydna, Telia, Valentina, Williana, and Yvanna.

In addition to the named storms, MFR tracked three other tropical systems that did not last for more than 24 hours. The first, designated Tropical Depression C1, formed on December 5 near the eastern portion of the basin, and quickly dissipated. The other two, designated E1 and H1, formed in January and February, respectively. In addition, Tropical Cyclone Willy crossed into the basin as a dissipating tropical depression, for which MFR did not issue advisories.

Systems

Moderate Tropical Storm Alexina

The first storm of the season formed from a low-pressure area with associated convection that persisted east of the Chagos Archipelago on November 7. It formed in tandem with two tropical depressions in the North Indian Ocean. The JTWC began tracking the system that day, although MFR did not follow suit until two days later. On November 10, the depression intensified into Moderate Tropical Storm Alexina, having developed a central dense overcast. A narrow eastward-moving trough caused the storm to move generally southward for its entire duration, the only such storm of the season to maintain a largely north–south track. On November 11, MFR estimated that Alexina attained peak winds of , while JTWC estimated peak winds of . Increased wind shear disrupted the convection, while a building ridge to the south caused its movement to slow. By late on November 12, Alexina weakened to tropical depression status, which subsequently drifted to the west until dissipating on November 16.

Severe Tropical Storm Bettina

On November 23, the Intertropical Convergence Zone spawned a low-pressure area in the far northeastern portion of the basin, which the JTWC assessed as having formed in the western Australian basin. Located north of a large ridge, the system tracked southwestward initially before turning more to the west. Late on November 25, MFR began classifying the system as a tropical disturbance, and within 12 hours the agency upgraded it to Moderate Tropical Storm Bettina. On November 26, the storm turned to the southwest. The next day, Bettina developed an eye feature, and MFR upgraded it to a severe tropical storm, with winds of . By comparison, the JTWC estimated winds of . After wind shear increased sharply on November 28, the storm quickly weakened and within 24 hours was devoid of convection. Bettina again turned to the west as a tropical depression, moving around the large ridge. It briefly re-intensified on December 1, but dissipated on December 3 south of the Mascarene Islands.

Severe Tropical Storm Cecilia

The Intertropical Convergence Zone spawned a tropical disturbance in the northeast portion of the basin on December 9. Initially the system did not develop, and MFR did not classify it until December 12. The next day, the depression intensified into a moderate tropical storm, and was named Cecilia. The strengthening was short-lived, and the storm quickly weakened to tropical depression status on December 14. After initially tracking to the southwest, Cecilia turned to the west on December 15 due to a strengthening ridge to the south, by which time it had restrengthened and developed a central dense overcast. On December 17, MFR upgraded the storm toa severe tropical storm, with winds of according to MFR. The next day, JTWC estimated that Cecilia intensified to reach winds of . While near peak intensity, the storm turned to the southwest and began weakening after wind shear increased. By December 19, Cecilia had weakened to tropical depression status, and dissipated on December 21 after passing west of Réunion. An approaching trough had caused thunderstorms to reform in the eastern portion of the circulation, which resulted in heavy rainfall over Mauritius and later Réunion. In the latter island, the rainfall was heaviest in the northern portion, peaking at in Salazie in 24 hours; the same station recorded in a 6-hour period, including in just 30 minutes.

Tropical Cyclone Daisy

In early January, the Intertropical Convergence Zone persisted off the northeast coast of Madagascar, spawning a low-pressure area on January 6. The next day, the system developed into a tropical disturbance, which initially moved to the east due to high pressure to the south. On January 8, the system developed a curved area of convection, which later developed into a central dense overcast. Initially located within a broader trough, the disturbance gradually became better defined as a distinct system. On January 10, it intensified into Moderate Tropical Storm Daisy while passing near St. Brandon. A trough to the south weakened the ridge, causing the storm to turn to the southwest toward Madagascar. Daisy intensified into a severe tropical storm on January 11, and later into a tropical cyclone the next day. At around 1200 UTC on January 13, the cyclone made landfall near Brickaville in eastern Madagascar, with MFR estimating winds of about ; at around the same time, the JTWC estimated peak winds of . At landfall, Daisy had a symmetrical cloud pattern in diameter. The high mountains of Madagascar caused the storm to quickly weaken, although it emerged into the Mozambique Channel as a tropical disturbance on January 15. That day, a trough turned Daisy to the south, and it briefly re-intensified into a tropical storm over warm waters. On January 16, Daisy made a second landfall in southern Madagascar and dissipated the next day.

When Daisy struck Madagascar, it produced wind gusts on Île Sainte-Marie, along with heavy rainfall. The storm destroyed over 90 schools and government buildings and damaged the road network. Madagascar's capital Antananarivo was flooded, forcing 6,000 people to evacuate. Many of the same areas affected by Daisy were later affected by Geralda in February.

Severe Tropical Storm Edmea

The Intertropical Convergence Zone spawned a low-pressure area south of the Chagos archipelago on January 12, and developed a large area of convection the next day. On January 13, MFR began classifying the system as a tropical depression, and following further intensification, the agency upgraded the depression to Moderate Tropical Storm Edmea later that day. With a ridge to the southeast, the storm tracked generally to the southwest. Its initial strengthening rate slowed until Edmea reached peak winds of on January 17. An approaching trough turned the storm to the south away from any landmasses, and also increased shear which caused weakening. Turning to the southeast on January 18, Edmea became extratropical the following day and was later absorbed by the trough.

Tropical Cyclone Pearl–Farah

On January 11, a tropical low formed northwest of Broome, Western Australia. It was named Pearl a few hours later by the Bureau of Meteorology. The cyclone continued westward and reached a peak intensity of . As the system moved west of 90°E, MFR took over warning responsibility on January 18 and renamed the cyclone Farah. At that time, MFR estimated winds of about . After having moved westward due to a ridge to the south, Farah turned to the south upon entering the basin due to an approaching trough, which previously absorbed Edmea. High wind shear caused rapid weakening, and by January 19, there was little remaining convection. The next day, Farah weakened to tropical depression status and turned to the southeast. The ridge built behind the trough, causing the depression to stall and drift northward, and by February 22, Farah dissipated.

Intense Tropical Cyclone Geralda

Cyclone Geralda originated from an area of low pressure from the monsoon trough on January 25. Over the following few days, the depression underwent gradual intensification, and MFR estimated peak winds of on January 31. Cyclone Geralda made landfall near Toamasina, Madagascar after weakening from its peak intensity. Within hours of moving onshore, the system had substantially weakened, and by February 5, Geralda had degenerated into a land depression. After briefly emerging into the Mozambique Channel, Geralda crossed southern Madagascar, and it became extratropical on February 8. Geralda was the strongest of the season and the strongest to hit Madagascar since a cyclone in March 1927.