Seasonal Climate Forecast

MAURITIUS METEOROLOGICAL SERVICES

Update of Summer 2022-2023 Outlook

for

Mauritius and Rodrigues

INTRODUCTION

This document is an update of the summer 2022-2023 outlook that was issued end of October 2022. It is based on latest information on the behaviour of meteorological and oceanic parameters (such as such as El Nino Southern Oscillation and Indian Ocean Dipole) and the observed deficient rainfall in November and December 2022 over Mauritius and Rodrigues.

UPDATE OF SUMMER 2022-2023 OUTLOOK

After careful analysis of the behaviour of all indicators and taking into consideration analogue
patterns, it is concluded that:
1) The onset of summer rain will be further delayed and is now expected during the second week of January 2023. The monthly rainfall for the month of January and February will be below normal. The cumulative summer rainfall is now expected to be below normal (70% of the Long Term Mean 1991-2010) with about 945 mm over Mauritius and around 490 mm over Rodrigues.

As from the second half of January to the end of April 2023, 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.
2) Temperatures will be close to normal. However, on certain days, it is likely that temperatures will exceed the long-term monthly average by more than two degrees Celsius. In such situation, the maximum temperatures during the day may reach 35 degrees Celsius along the western coasts. At Rodrigues on certain occasions, the maximum temperatures during the day may reach 32 degrees Celsius along coastal areas. Occasional above normal temperatures together with prolonged periods of high humidity and light wind conditions, may result in torrid conditions particularly during the months January to March that will cause severe discomfort mainly to the vulnerable groups of the population.

3) The number of named storms evolving in the South West Indian Ocean basin for the 2022- 2023 cyclone season (01 November 2022 to 15 May 2023) is likely to be between seven (7) and nine (9). As observed, the eastern part of the basin has been more conducive for cyclone formation. So far, two (2) storms have already been named by the Mauritius Meteorological Services during the month of September and October 2022 and a third one was named in December 2022 by the Australian Bureau of Meteorology. During the second half, the western part of the basin will also become favourable for storm formation.
4) The impacts of Global Warming are being felt worldwide including the South West Indian Ocean region where the frequency of extreme weather and climate events is increasing since the last few decades. The Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) states the global surface temperature will continue to rise resulting in larger changes in climate systems. Consequently, extreme weather events in the form of heavy rainfall leading to flash flood, violent thunderstorms, electric storms, mini tornadoes, rapid intensification of tropical cyclones may occur during summer 2022-2023.
5) Heavy swells generated by tropical cyclones evolving in the vicinity of the Mascarene Islands may affect the shores of the islands of the Mauritius, Rodrigues, Agalega and St Brandon.

Note:

1) All named storms that will develop in the Southwest Indian Ocean will NOT necessarily be a direct threat to the islands of the Mauritius, Rodrigues, Agalega and St Brandon; and
2) All cyclones/storms will have a unique name in the southern Indian Ocean.

Disclaimer:
The Summer Outlook gives an indication of the expected evolution of the 2022-2023 South West Indian Ocean (SWIO) summer namely: cyclone activity, summer rain and temperature in Mauritius and Rodrigues. It is a climate forecast that estimates the likelihood of the climatic events in the coming months and is NOT an attempt to forecast the detailed day-to-day evolution of the weather. The contents of this 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.

This report may be updated upon the availability of fresh information.

Mauritius Meteorological Services

28 December 2022

Vacoas