Seasonal Climate Forecast
Summer 2019-2020 Outlook
Mauritius and Rodrigues
This report gives an indication of the expected evolution of the 2019-2020 South-West Indian Ocean (SWIO) summer - namely, the likely cyclone activity, summer rains and temperatures in Mauritius and Rodrigues.
Summer season in the Republic of Mauritius is from 01 November to 30 April of the following year. However, the official cyclone season is from 01 November to 15 May.
The start of the summer rain is defined as the first occasion after 01 November that the seven-day total is equal to or exceeds 50mm and includes at least four rainy days.
The contents of this outlook are meant to be used as general guidelines for planning purposes by stakeholders in various sectors.
2.0 General Background
A seasonal climate forecast aims to estimate the change in the likelihood of a climatic event happening in the coming months.
A seasonal forecast can provide information on how likely it is for the coming season to be wetter, drier, warmer or colder than the normal.
A seasonal climate forecast is not an attempt to forecast the detailed day to day evolution of weather.
Outputs from dynamic climate models as well as persistence and the behaviour of meteorological and oceanic parameters in analogous years have been utilised to generate the most likely scenario for the 2019-2020 Southwest Indian Ocean summer. Global, regional and local predictors are analysed during the process of preparation of this outlook.
3.0 Extreme Weather and Climate Events
The impacts of Global Warming are being felt worldwide including the South-West Indian Ocean where the frequency of extreme weather and climate events is increasing since the last few decades.
The latest findings of the Special Report on Global Warming of 1.5 'C (SR15) above pre-industrial level confirmed the above observations.
It is therefore very likely that extreme weather events in the form of heavy/torrential rain, violent thunderstorms, electric storms, mini tornadoes, rapid intensification of tropical cyclones may occur during the coming summer and cyclone season 2019-2020. Short duration heavy rain will result in localised flash floods.
High waves generated by tropical cyclones evolving in the vicinity of the Mascarene Islands may reach the shores of the islands of the Republic of Mauritius.
After careful analysis of the behaviour of all indicators and taking into consideration analogue patterns, it is concluded that:
1) Mean air temperature will be above normal during summer 2019-2020. However, on certain days, temperature may exceed the monthly mean by more than three degrees Celsius in some locations. Maximum day temperatures may reach 36oC at Port Louis and along the western coasts during peak summer months.
At Rodrigues, maximum temperatures may reach 33oCalong coastal areas on certain occasions.
Above normal temperatures, coupled with prolonged periods of high humidity and light wind conditions, will result in torrid conditions particularly during the months of January to March, causing severe discomfort.
2) The onset of summer rain will be in the second fortnight of December.
Total summer rainfall is expected to be near normal with about 1400 mm over Mauritius and around 700mm over Rodrigues.
3) During peak summer months, January to March 2020, atmospheric conditions will be conducive to the occurrence of extreme weather events such as heavy/torrential rain, heat wave and violent thunderstorms. Short duration heavy rainfall will cause localised flash floods.
4) The number of named storms evolving in the South-West Indian Ocean basin for the 2019-2020 summer season, i.e. from 01 November 2019 to 15 May 2020 is likely to be 8 to 10. During this season, the region to the West of Diego Garcia is likely to be more conducive to storm formation.
There is a probability of having the first named storm in the Southwest Indian Ocean basin by the end of November.
1. All named storms that will develop in the South-West Indian Ocean will NOT necessarily be a direct threat to the islands of the Republic of Mauritius.
2. All storms/cyclones will have a unique name in the southern Indian Ocean. A storm/cyclone originating from the Australian region and entering the Area of Responsibility of Mauritius will retain its original name and vice versa.
This report may be updated upon the availability of fresh information.
St Paul Road, Vacoas
Date: 04 November 2019