DRR (Tropical Cyclones)

What is a tropical cyclone?

Meaning of common terms used

A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined centre.  Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere.

Naming of tropical storms in the South West Indian Ocean Basin

The system of naming tropical cyclones was introduced in 1960, which will be remembered as the year during which Mauritius was struck by cyclone “Alix” and by cyclone “Carol”, the most devastating cyclone on record. Madagascar, Reunion, Seychelles, Comores, and Mauritius use a common list of names for identifying tropical storms. Mauritius is responsible for naming storms forming in the region lying between longitude 55ºE and 90ºE. Madagascar is responsible for the region west of longitude 55ºE and the Australian Bureau of Meteorology for the region east of 90ºE. Whenever a cyclone moves from the Australian region of responsibility to that of Mauritius, it keeps its Australian name as per decision of the Tropical Cyclone Committee held in Nairobi in 2010.

Season and Lifecycle

Occurrence

Approximately 10% of the world's tropical cyclones originate in the Southwest Indian Ocean near Mauritius. The figure presents the average annual occurrence of tropical cyclones in this region. Situated at the tail end of the Indian Ocean cyclone belt, Mauritius has typically faced fewer cyclones historically. From 1960 to 1969, the average was 2.4 cyclones per year. However, this average increased to 5.1 cyclones per year from 2000 to 2009, demonstrating that the frequency of tropical cyclones nearly doubled over the span of four decades. Nonetheless, a 2020 US study highlighted a significant shift, showing an 18% increase per decade in the likelihood of major tropical cyclones in the region- see Figure

Although many cyclones do not make direct landfall, the islands frequently experience the effects of large storms, resulting in annual flooding in low-lying areas and extensive damage to infrastructure, buildings, crops, and livestock. Additionally, the average frequency of intense cyclones—with wind gusts surpassing 165 km/h—increased from 3.9 between 1981 and 2020 to 4.7 between 1991 and 2020. Current forecasts also predict a future increase in cyclone intensity occurring over shorter durations. 

Movement of Tropical Cyclone Occurrence Average in Southwest Indian Ocean every 10 years

Notable Tropical Cyclones Affecting Mauritius

• TC Carol (1960): One of the most devastating cyclones to hit Mauritius, causing significant destruction and loss of life.
• TC Gervaise (1975): The severe cyclone is remembered for its widespread damage across the island, including severe impacts on infrastructure and the economy.
• TC Hollanda (1994): This cyclone is notable for being one of the strongest to strike Mauritius in recent decades, causing extensive damage to the north of the island.
• TC Dina (2002): A powerful cyclone that brought heavy rains and strong winds, resulting in considerable damage.
• TC Berguitta (2018): Berguitta passed close to Mauritius, causing flooding and disruptions but less structural damage due to improved preparedness and building standards.
• TC Belal (2024): Belal passed close to Mauritius, halting flights and mandating home stay except for essential personnel, as the storm brought high winds, heavy rain, and led to two fatalities, affected 100,000 people, and caused infrastructure damage and flooding through January 16, prompting evacuations of some 1000 people, brief power outages for some 40,000 people, and emergency assessments and support by local authorities and health workers.
• TC Garance (2025): Intense Tropical Cyclone Garance was a powerful tropical cyclone which impacted Réunion and Mauritius. The seventh named storm and fifth intense tropical cyclone of the 2024–25 South-West Indian Ocean cyclone season, Garance originated from a tropical disturbance which was spotted on 24 February to the east of Madagascar. The cyclone caused adverse weather conditions on the island. High swell warnings were issued.

List of Tropical storms/cyclones when warnings were issued for Island of Mauritius since 1991

Impacts

When a cyclone strikes, it can inflict widespread damage on a nation, leading to significant numbers of victims and extensive economic losses. In Mauritius, where the population is densely concentrated and economic activities are robust, the severe damage caused by tropical cyclones is a critical factor in major setbacks to social and economic development.

The accompanying table lists the damages caused by natural disasters in Mauritius from 1960 to 2009, highlighting the tropical cyclones shown in the figure (tracks of the most severe cyclones that affected Mauritius) marked in red. Cyclone Fantala in 2016, which led to evacuations on Agalega’s South Island, highlight these ongoing challenges. More recently, Cyclones Berguitta and Gelena in 2019 caused extensive damage, power outages, and forced many people from their homes.

Mauritius is expected to face about $91 million in direct annual losses due to winds, flooding, and storm surges from tropical cyclones. Half of these losses typically affect the residential sector, while nearly 30% impact the commercial sector. The costs related to emergency responses to tropical cyclones are estimated to average nearly $21 million annually. Over a 100-year period, the projected losses for Mauritius from tropical cyclones could reach $1.9 billion. Rodrigues Island is predicted to experience even more severe effects, with potential 100-year storm winds surpassing 200 km/h, compared to the current maximum of 165 km/h. Flooding in Mauritius, exacerbated by tropical cyclones, is also expected to worsen under these projections (RoM 2021). 

Projections 

Projections indicate that:

• Decrease in Total Cyclones: The overall number of tropical cyclones is expected to decrease by the end of the century.
• Increase in Cyclone Intensity: Human-induced warming is likely to make cyclones more intense, with wind speeds increasing by:
  1. 2–11% under the mid-range scenario (RCP4.5)
  2. About 5% for a 2ºC global warming
• Frequency of Intense Storms: The occurrence of the most intense storms (categories 4 and 5) is projected to become more frequent -  this is sensitive to the spatial resolution of the models used.
• Increase in Rainfall Rates: Average precipitation rates within 100 km of the storm center are likely to increase by up to 10% per degree of warming.
• Impact of Slower Cyclone Speeds: If tropical cyclone translation speeds continue to decrease, the increases in rainfall rate could be exacerbated.

Cyclone Preparedness 

• Early Warning Systems: Mauritius Meteorological Services provides early warnings and regular updates during the cyclone season to ensure public safety and preparedness.
• Public Education and Drills: Regular public education campaigns and drills help ensure that the population is prepared for cyclone events.
• Emergency Management: Mauritius has a well-coordinated emergency/crisis management system. The National Emergency Operations Command is activated in the event of a cyclone, including pre-positioning of resources, evacuations if necessary, and post-cyclone recovery and assistance and the National Crisis Committee take decisive and timely actions as per Section 17 and 16 of the NDRRMC Act 2016.

Infrastructure and Building Codes: Over the years, building codes have been strengthened to withstand cyclonic conditions, which has helped reduce the damage from more recent cyclones.
 

RADAR installed at Trou aux Cerfs, Curepipe

Useful Links (MMS)

• List of Historical Cyclones
• Current Storm/Cyclone
• Cyclone Warning Bulletin Mauritius
• Cyclone Warning Bulletin Rodrigues
• Warning System and General Info
• Precautions
• Cyclone Names
• Satellite Imagery
• Satellite Animation
• Synoptic Chart
• Radar Imagery