This Seasonal Outlook gives an indication of the expected evolution of the 2024-2025 South West Indian Ocean (SWIO) summer namely: cyclone activity, summer rain and temperature in Mauritius and Rodrigues. This is a climate forecast and is NOT an attempt to forecast the detailed day-to-day evolution of the weather. The contents of the seasonal outlook are meant to be used as general guidelines for planning purposes by stakeholders in various sectors and for information to the public at large.
Background
Summer season in Mauritius, Rodrigues, Agalega and St Brandon is from 01 November to 30 April of the following year. However, the official cyclone season is from 01 November to 15 May of the following year.
The behaviour of meteorological and oceanic parameters such as El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and the behaviour of meteorological and oceanic parameters in analogue years have been utilised to generate the most likely scenario for the 2024-2025 Southwest Indian Ocean summer. Global, regional and local predictors have also been analysed in the process of the preparation of this outlook.
Conclusion
After careful analysis of the behaviour of all indicators and taking into consideration analogue patterns, it is concluded that:
1. Temperatures will be slightly above the normal during summer 2024-2025. On certain days, it is likely that temperatures will exceed the long-term monthly average by more than two to three degrees Celsius. In such situation, the maximum temperatures during the day may reach 35oC along the western coasts.
At Rodrigues on certain occasions, the maximum temperatures during the day may reach 33oC along coastal areas. Above normal temperatures together with prolonged periods of high humidity and light wind conditions, may result in torrid conditions particularly during the months of January to March 2025 that will cause severe discomfort mainly to the vulnerable groups of the population.
2. The onset of summer rain is expected to be on time, that is during the second fortnight of December 2024. The cumulative summer rainfall over Mauritius is expected to around 80% of the normal, amounting to about 1100 mm. For Rodrigues, the cumulative rainfall during summer will be around 85% of the normal, which amounts to about 600 mm.
3. The number of named storms evolving in the South West Indian Ocean basin for the 2024-2025 cyclone season is likely to be between eleven (11) and thirteen (13). During this season the central and western equatorial region of the basin is more conducive for cyclone formation, with a few in the Mozambique Chanel.
4. Heavy swells generated by tropical cyclones evolving in in the vicinity of the islands of Mauritius may affect their shores. The cyclones may also cause storm surges if they pass very close to the islands.
5. During January to March 2025, atmospheric conditions will become conducive to the occurrence of extreme weather events such as violent thunderstorms and heavy rainfall. Short-duration heavy rainfall will cause localised flash floods.
6. In addition, it is very likely that other extreme weather events in the form of warm spells, heavy/torrential rain, violent thunderstorms, electric storms, mini tornadoes, rapid intensification of tropical cyclones may occur. Short-duration high-intensity rainfall will result in localised flash floods.
Note:
a. The named storms that are likely to develop in the Southwest Indian Ocean will NOT necessarily be a direct threat to the islands of the Mauritius, Rodrigues, Agalega and St-Brandon;
b. All cyclones/storms will have a unique name in the southern Indian Ocean; and
c. This report may be updated upon the availability of fresh information.
Date of release: 25 October 2024
©Mauritius Meteorological Services
