Phénomène « La Niña » : Maurice plus chaud cet été

Courant descendant dans la région des Mascareignes, le phénomène « La Niña » prévient la formation des nuages, causant une pluviométrie inférieure à la moyenne. Maurice, qui est actuellement sous son influence, connaîtra un été plus chaud cette année. Notamment avec une température avoisinant les 35°C. D’ailleurs entre sept et neuf cyclones sont attendus.

« C’est un des paramètres faisant que nous prévoyons une pluviométrie en dessous de la moyenne. Mais, il y a parallèlement un autre élément tout aussi important. Celui de la température inférieure au sud des Mascareignes. C’est ce qui explique la grande sècheresse au sud de Madagascar », explique le prévisionniste Prem Pathak. De plus, selon la station météo de Vacoas, dans son Summer Outlook 2020-2021, un tourbillon, en gestation près de l'Indonésie
actuellement, pourrait devenir une dépression tropicale.

Ci-dessous le rapport Summer Outlook 2020-2021 :

Summer 2020-2021 Outlook for Mauritius and Rodrigues

Introduction

This report gives an indication of the expected evolution of summer 2020-2021, namely; the likely cyclonic activity, summer rain and temperature in Mauritius and Rodrigues.

Summer season in the Republic ofMauritius 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 rainfall is equal to or exceeds 50 mm and includes at least four rainy days.

The content of this outlook is meant to be used as general guidelines for planning purposes by stakeholders in various sectors.

General Background

A seasonal climate forecast

aims to estimate the change in the likelihood of a climatic event happening in the coming months and is not an attempt to forecast the detailed day to day evolution of weather.
can provide information on how likely it is for the coming season to be wetter, drier, warmer or colder than the normal.

Global, regional and local predictors are analysed during the process of preparation of this outlook. Outputs from dynamic climate models as well as persistence, behaviour of meteorological and oceanic parameters in analogous years have been utilised to generate the most likely scenario for the 2020-2021 Southwest Indian Ocean summer.

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 â—¦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 rainfall and rapid intensification of tropical cyclones may occur during the coming summer 2020-2021.

Extreme weather events mean weather which disturbs social and economic activity or the well-being of the population.

Conclusions

After careful analysis of the behaviour of all indicators and taking into consideration analogue patterns, hereunder, is the most likely scenario for Summer 2020-2021:

1.The onset of summer rain will be slightly delayed. The expected start of summer rains will be around the last week of December 2020.

Rainfall for the first half of summer will be slightly below the long-term mean. There is an indication that it will decrease further during the second half. The cumulative summer rainfall over Mauritius is expected to around 1,050 mm which is below the normal. (The normal 1981-2010 summer rainfall is about 1331 mm).

The cumulative rainfall over Rodrigues will be slightly below normal as well with around 650 mm compared to the long term mean of 700 mm.

2. Mean air temperature for Mauritius will be slightly above normal during the first half of summer and close to the mean during the second half. However, on certain days, temperature may exceed the monthly mean by more than three degrees Celsius in some locations. Maximum day temperature may reach 35oC at Port Louis and along the western and northern coasts during peak summer months.

Occasionally above normal temperatures, coupled with prolonged periods of high humidity and light wind conditions, may cause severe discomfort.

At Rodrigues, maximum temperatures may reach 33oC along coastal areas on certain occasions.

3. Occasionally, atmospheric conditions will be conducive to the occurrence of extreme weather events such as heavy or torrential rainfall and heat wave. Short duration heavy rainfall is likely to cause localised flash floods.

4. The number of named storms evolving in the South West Indian Ocean basin for the 2020-2021 summer season, that is, from 01 November 2020 to 15 May 2021 is likely to be between 7 and 9.

During this season, the preferred region of cyclogenesis will be in the central Indian Ocean around Diego Garcia and to the east of Diego Garcia.

It is likely that the first named storm will occur by last week of December 2020 or first week of January 2021.

However, most models are developing a low pressure area to the southeast of Diego Garcia by 15 November 2020. There is a chance that the low may deepen into a tropical depression at the start of the second fortnight of November 2020.

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 Republic of Mauritius.