| First storm formed | October 5, 2017 |
| Last storm dissipated | Season currently active |
| Strongest storm | Cherono — 165 mph, 889 mbar |
| Total disturbances | 13 |
| Tropical depressions | 12 |
| Total storms | 9 |
| Tropical cyclones | 5 |
| Intense cyclones | 3 |
| Total damages | $4.2 billion (2018 USD) |
| Total fatalities | 770 |
The 2017-18 South-West Indian Ocean cyclone season was a hyperactive season, with 31 named storms and 23 tropical cyclones. It began on November 1, 2017, and ended on April 30, 2018, dates which conventionally delimit the year in which most tropical cyclones form in the basin. However, any tropical cyclone that developed between July 1, 2017, and June 30, 2018, would have counted towards the seasonal count. The South-West Indian Ocean basin is defined as being to the south of the equator and between the coast of Africa and 90°E. The basin is monitored by Meteo France in Réunion (MFR), while the Madagascan Weather Service (MWS) and Mauritius Meteorological Service (MMS) name tropical cyclones when they reach moderate tropical storm intensity. The Joint Typhoon Warning Center (JTWC) also issue warnings for the basin, designating tropical cyclones with a number and an "S" suffix.
Season summary[]
Storms[]
Tropical Disturbance 01[]
| Tropical disturbance (MFR) | |
 | |
| Duration | October 5 – October 14 |
|---|---|
| Peak intensity | 30 mph (45 km/h) (1-min) 999 mbar (hPa) |
A zone of disturbed weather (ZDW) was first mentioned in La Reunion's Tropical Weather Outlook (TWO) on October 3. They said that it would slowly strengthen into a tropical disturbance and then later a tropical depression. The ZDW then strengthened into a tropical disturbance on October 5, less than a month before the official start to the South-West Indian Ocean (SWIO) cyclone season. However, due to strengthening wind shear, the system was no longer forecast to become a tropical depression. The disturbance was stationary until October 14, when a system in the North Indian Ocean absorbed 01.
Tropical Depression 02[]
| Tropical depression (MFR) | |
 | |
| Duration | October 31 (moved into basin) – November 3 |
|---|---|
| Peak intensity | 35 mph (55 km/h) (1-min) 1002 mbar (hPa) |
A tropical low formed north of Exmouth, Australia on October 24 where tropical cyclone watches had been issued. Those were immediately cancelled when the low was then forecast to move into the SWIO basin. Once the system had crossed 90°E, the system was numbered 02 by the MFR and was classified as a tropical depression on October 31. The next day, the depression had turned to the south and started to encounter cooler sea surface temperatures (SST). However, the system maintained intensity until November 3 when it became an extratropical cyclone.
Intense Tropical Cyclone Abele[]
| Intense tropical cyclone (MFR) | |
 | |
| Duration | November 12 – November 19 |
|---|---|
| Peak intensity | 105 mph (165 km/h) (1-min) 959 mbar (hPa) |
A ZDW formed east of Madagascar on November 12 and rapidly strengthened into a tropical depression and was numbered '03'. Hours later, the JTWC had issued a Tropical Cyclone Formation Alert (TCFA) on the system. During the morning hours of November 13, Tropical Depression 06 had strengthened into Moderate Tropical Storm Abele and the JTWC began issuing warnings on 02S. The storm rapidly strengthened on November 15, when Abele became a tropical cyclone. Additional strengthening occurred during the night of November 15–16, when the cyclone became an intense tropical cyclone, with 10-min sustained winds of 105 mph. It began weakening due to cooler SSTs and higher wind shear. By November 18, the storm was just located south-west of Madagascar as a minimal moderate tropical storm. This prompted the JTWC to issue its final warning on Abele. It rapidly weakened to a tropical disturbance on November 19 and dissipated. No watches or warnings were issued due to Abele.
Severe Tropical Storm Bingiza[]
| Severe tropical storm (MFR) | |
 | |
| Duration | November 25 – November 29 |
|---|---|
| Peak intensity | 70 mph (110 km/h) (1-min) 981 mbar (hPa) |
The MFR had noted a small low-pressure area located in the Mozambique Channel on November 24, which became a tropical depression the next day. A Cyclone Warning was issued for Mozambique at 0600 UTC on November 26 as the depression strengthened into Moderate Tropical Storm Bingiza. As the storm neared the Mozambique coast, 15,000 people were evacuated from the coastline. Soon after, Bingiza strengthened into a severe tropical storm with winds of 70 mph. At 0745 UTC on November 28, Bingiza made landfall near Beira, causing widespread flooding. The system rapidly weakened into a ZDW and dissipated on November 29.
Bingiza caused $3.2 billion in damage and killed 129 people. Due to this, Bingiza was retired during the summer of 2018.
Very Intense Tropical Cyclone Cherono[]
| Very intense tropical cyclone (MFR) | |
 | |
| Duration | December 8 – December 24 |
|---|---|
| Peak intensity | 165 mph (270 km/h) (1-min) 889 mbar (hPa) |
A low-pressure system formed about 1,015 miles east of La Reunion on December 8 and gained a circulation hours later. At 1200 UTC on December 28, RSMC La Reunion classified this system as a Moderate Tropical Storm, and Mauritius named the storm Cherono. The system rapidly strengthened to tropical cyclone strength in 12 hours and strengthened again to an intense tropical cyclone six hours later. In the afternoon hours of December 9, the JTWC had issued a TCFA on the system, while only hours later designating the system as '03S'. At the same time, RSMC La Reunion had upgraded Cherono to a Very Intense Tropical Cyclone, with winds of 150 mph and a central pressure of 901 mb. It strengthened even further on December 12, when it had become the strongest South-West Indian Ocean cyclone ever recorded with a central pressure of 889 mb.
Tropical Depression 06[]
| Tropical depression (MFR) | |
| | |
| Duration | December 11 – December 12 |
|---|---|
| Peak intensity | 35 mph (55 km/h) (1-min) 1006 mbar (hPa) |
A tropical depression formed on December 11 south of La Reunion with 10-min sustained winds of 35 mph. However, early on December 12, the depression was absorbed by much larger Cyclone Cherono.
Tropical Cyclone Dalilou[]
| Tropical cyclone (MFR) | |
| | |
| Duration | December 16 (moved into basin) – December 19 |
|---|---|
| Peak intensity | 75 mph (120 km/h) (1-min) 988 mbar (hPa) |
A tropical low formed in the Australian region on December 3, and then on December 11, made landfall near Darwin. The storm caused 13 deaths and $6.4 billion in damage in Australia. The storm then moved across Western Australia and into the SWIO on December 16. It already had sustained winds of 35 mph, and was classed as a tropical depression. It slowly strengthened into a moderate tropical storm on December 17, with Mauritius naming it Dalilou. It strengthened more in twelve hours and became a severe tropical storm. On December 18, Dalilou strengthened into a tropical cyclone with winds of 75 mph. The next day, Dalilou became extratropical, however, it still had winds equivalent to a tropical cyclone. The extratropical remnants of the storm moved southwards rapidly until dissipating north of Vostok, Antarctica on December 24.
Moderate Tropical Storm Elvire[]
| Moderate tropical storm (MFR) | |
| | |
| Duration | December 20 – December 22 |
|---|---|
| Peak intensity | 45 mph (75 km/h) (1-min) 997 mbar (hPa) |
A tropical disturbance formed on December 20 just off the coast of Mauritius and strengthened into a tropical depression. Over 23 inches of rain was recorded in Bel Air, Mauritius, while 20 inches was recorded in Goodlands. Three people died due to the floods, according to officials. By December 21, the depression had strengthened into Moderate Tropical Storm Elvire. Shortly after, the storm made landfall on Mauritius and weakened significantly and dissipated the next day.
Severe Tropical Storm Francis[]
- Main article: Tropical Storm Francis
| Severe tropical storm (MFR) | |
| | |
| Duration | December 28 – January 3 |
|---|---|
| Peak intensity | 65 mph (100 km/h) (1-min) 969 mbar (hPa) |
On December 28, RSMC La Reunion reported that a tropical disturbance had developed about 71 miles north-west of Anorotsangana. Six hours later, it had strengthened into a depression, and later a moderate tropical storm and was named Francis. The RSMC began issuing Cyclone Warnings for the northwestern Madagascar coast and cyclone watches for the west coast. The storm maintained its strength until January 3, when it strengthened into a Severe Tropical Storm. It made landfall near Antananabe, Madagascar at 1923 UTC. It weakened rapidly and dissipated by the next advisory at 0000 UTC on January 4.
Tropical Depression 10[]
| Tropical depression (MFR) | |
| | |
| Duration | December 30 – January 2 |
|---|---|
| Peak intensity | 35 mph (55 km/h) (1-min) 994 mbar (hPa) |
The RSMC La Reunion reported that a tropical depression had formed about 620 miles northeast of Mauritius on December 30. However, an area of thunderstorms that had developed earlier in the day had absorbed the depression on January 2.
Five people that were aboard a ship died due to the ship sinking.
Very Intense Tropical Cyclone Haingo[]
- Main article: Cyclone Haingo
| Very intense tropical cyclone (MFR) | |
 | |
| Duration | January 4 – January 8 |
|---|---|
| Peak intensity | 145 mph (230 km/h) (1-min) 903 mbar (hPa) |
A Moderate Tropical Storm formed on January 4, and six hours later, strengthened into a Very Intense Tropical Cyclone with winds of 145 mph, making it the fastest intensifying SWIO storm ever recorded. It maintained its peak strength until January 5, when it weakened to a Category 2 due to an eyewall replacement cycle. However, this did not last long as Haingo restrengthened back to a Category 4. Due to increasing wind shear, the cyclone began to weaken during that evening and was down to a Tropical Cyclone by January 5. Slight restrengthening occurred later that day, where Haingo reached a third peak of 115 mph winds. The system then weakened as it picked up forward speed, and dissipated on January 8 as a Moderate Tropical Storm.
Tropical Cyclone Igor[]
| Tropical cyclone (MFR) | |
| | |
| Duration | January 12 – January 21 |
|---|---|
| Peak intensity | 85 mph (140 km/h) (1-min) 949 mbar (hPa) |
A deep low-pressure system had formed north-east of Mauritius, and developed into a moderate tropical storm six hours later, assigning the name Igor. The storm strengthened further on January 15, when it became a severe tropical storm with sustained winds of 70 mph. The next day, Igor became a tropical cyclone and made landfall on Mauritius, bringing power outages that lasted for over a week. It maintained its intensity until January 19, when it began to weaken due to increasing wind shear. Igor eventually dissipated on January 21.
Moderate Tropical Storm Jani[]
| Moderate tropical storm (MFR) | |
 | |
| Duration | January 22 – January 25 |
|---|---|
| Peak intensity | 50 mph (85 km/h) (1-min) 992 mbar (hPa) |
RSMC La Reunion noted that an area of convection had persisted in the northern Mozambique Channel. A few hours later, the center upgraded the area of convection to Tropical Depression 13. However, the system was shortly downgraded to a tropical disturbance as wind shear increased.
The system regained its convection and reattained its circulation, and was upgraded to a Moderate Tropical Storm, with NWS Madagascar naming it Jani.
Season effects[]
This table lists all the storms that developed in the Southern Hemisphere during the 2017–2018 South-West Indian Ocean cyclone season. It includes their intensity, duration, name, landfalls, deaths, and damages. All data is taken from Météo-France. The damage figures are all from 2018 USD.
| Storm Name |
Dates active | Storm category at peak intensity |
Peak 10-min sustained winds |
Pressure hPa |
Areas affected | Damage (USD) |
Deaths | |
|---|---|---|---|---|---|---|---|---|
| 01 | N/A | October 5 –14 | Tropical Disturbance | 45 km/h (30 mph) | 999 | None | None | None |
| 02 | N/A | October 31 – November 3 | Tropical Depression | 55 km/h (35 mph) | 1002 | None | None | None |
| 03/02S | Abele | November 12 – 19 | Intense Tropical Cyclone | 165 km/h (105 mph) | 959 | Madagascar | None | None |
| 04 | Bingiza | November 25 – 29 | Severe Tropical Storm | 110 km/h (70 mph) | 981 | Madagascar, Mozambique | $3.2 billion | 129 |
| 05/03S | Cherono | December 8 – 24 | Very Intense Tropical Cyclone | 265 km/h (165 mph) | 889 | None | None | None |
| 06 | N/A | December 11 – 12 | Tropical Depression | 55 km/h (35 mph) | 1006 | Reunion | None | 1 |
| 07/06S | Dalilou | December 16 – 19 | Tropical Cyclone | 120 km/h (75 mph) | 988 | None | None | None |
| 08 | Elvire | December 20 – 22 | Moderate Tropical Storm | 75 km/h (45 mph) | 997 | Mauritius, Reunion | $600 million | 3 |
| 09/11S | Francis | December 28 – January 3 | Severe Tropical Storm | 100 km/h (65 mph) | 969 | Madagascar | $300 million | 631 |
| 10 | N/A | December 30 – January 2 | Tropical Depression | 55 km/h (35 mph) | 994 | None | None | 5 |
| 11/14S | Haingo | January 4 – January 8 | Very Intense Tropical Cyclone | 230 km/h (145 mph) | 903 | Reunion | None | None |
| 12/17S | Igor | January 12 – 21 | Tropical Cyclone | 140 km/h (85 mph) | 949 | Reunion | $100 million | 1 |
| 13/19S | Jani | January 22 – 25 | Moderate Tropical Storm | 85 km/h (50 mph) | 992 | Mozambique, Madagascar | None | None |
| Season Aggregates | ||||||||
| 12 systems | October 5 – active | 265 km/h (165 mph) | 889 | $4.2 billion | 770 | |||