Seasonal Climate Forecast
MAURITIUS METEOROLOGICAL SERVICES
Summer 2018-2019 Outlook
Mauritius and Rodrigues
This report gives an indication of the expected evolution of the 2018-2019 South West Indian Ocean (SWIO) summer - namely, the likely cyclone activity, summer rains and temperatures in Mauritius and Rodrigues.
The official cyclone season for the Republic of Mauritius is from 01 November to 15 May of the following year.
The Start of the Rains is defined as the first occasion after the first of November that the seven-day total is equal to or exceeds 50 mm 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.
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 that the coming season will be wetter, drier, warmer or colder than 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 analogue years have been utilised to generate the most likely scenario for the 2018-2019 Southwest Indian Ocean summer. Global, regional and local predictors are analysed during the process of preparation of this outlook.
Extreme Weather and Climate Events
Regional and global observations over the past two decades as well as scientific reports indicate that the frequency of extreme weather and climate events has increased in the Southwest Indian Ocean.
The latest findings of the Special Report on Global Warming of 1.5 oC (SR15) above pre-industrial level confirmed the above observations. As such, it is very likely that similar events in the form of heavy/torrential rainfall leading to flash floods and violent thunderstorm, and explosive intensification of cyclones may occur during the forthcoming summer 2018-2019. Tropical cyclones evolving in the vicinity of the Mascarenes Islands may generate high waves that are likely to reach the shores of the Islands of the Republic of Mauritius.
After careful analysis of the behaviour of all predictors and taking into consideration analogue patterns, it is concluded that:
1) Temperatures will be slightly above normal during summer 2018-2019. However, on certain days, temperatures will exceed the monthly average by more than two degrees Celsius in some locations. Maximum day temperatures may reach 36oC at Port Louis and along the Western coast during peak summer months.
At Rodrigues, maximum temperatures may reach 33 degrees Celsius along coastal areas on certain occasions.
Above normal temperatures, coupled with prolonged periods of high humidity and light wind conditions, may result in torrid conditions particularly during the months of January to March 2019. These conditions may lead to severe discomfort to the vulnerable groups of the population.
2) The onset of summer rains will most likely be in the second fortnight of December 2018.
Cumulative summer rainfall is expected to be near normal with about 1400 mm over Mauritius and around 750 mm over Rodrigues. However, there may be marked intra-seasonal variation with dry spells followed by wet spells characterised by heavy short duration rainfall.
3) During January to March 2019 atmospheric conditions will become conducive to the occurrence of extreme weather events such as torrential rains, flash floods, heat wave and violent thunderstorms.
4) The number of named storms evolving in the South West Indian Ocean basin for the 2018-2019 summer season will be slightly below normal to near normal, that is, between 7 and 9 tropical storm/cyclone formations. During this season, the preferred region of cyclogenesis will be west of 75 degrees east (the central tropical Indian Ocean and between Diego Garcia and Agalega).
1. All named storms that will develop in the Southwest Indian Ocean will NOT necessarily be a direct threat to the islands of the Republic of Mauritius.
2. All cyclones/storms will have a unique name in the southern Indian Ocean (A cyclone/storm 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.
24 October 2018