Seasonal Climate Forecast

MAURITIUS METEOROLOGICAL SERVICES 

Seasonal Outlook for Winter 2022 

1.0 Introduction 

This Seasonal Outlook gives an insight of the expected evolution of the Winter in 2022 over  Mauritius and Rodrigues. The content of this outlook is meant to be used as general guidance for  planning purposes by stakeholders in various socio-economic sectors.  

 

2.0 Background 

A seasonal climate forecast aims to estimate the likelihood of a climatic event happening in the  coming months. The seasonal forecast provides information on how likely it is that the coming  season will be wetter, drier, warmer or colder than normal. A climate forecast is not an attempt to  forecast the detailed day-to-day evolution of weather. 

Winter season in Mauritius and Rodrigues occurs from May to October. The weather during  Winter is often characterised by persistent trade winds emanating from anticyclones transiting the  South Indian Ocean from west to east. Temperatures are cooler, especially during the months of  June to September. May and October are generally considered as transition months.  

The behavior of meteorological and oceanic parameters such as El Nino Southern Oscillation  (ENSO) and the identification of analogue years are the key factors used to generate the most  likely scenario for the winter. Global, regional and local predictors are analysed in the process of  the preparation of this outlook. 

 

3.0 The Past Summer 2021-2022 

The El Nino Southern Oscillation (ENSO) transited from a Neutral condition into weak la Nina in  the month of October 2021 and prevailed during Summer 2021-2022.  

A neutral Indian Ocean Dipole was observed in the Equatorial Indian Ocean for Summer 2021- 2022.  

Onset of Summer 2021-2022 rainfall over Mauritius was delayed and it started in the last week of  December 2021.  

November 2021 was the driest November on record since 1904, with 15 percent of monthly rainfall  compared to the Long-Term Mean (1991-2020). Rainfall was normal for the months of December  2021 and January 2022 and it was above normal for the remaining months of the season (February 2022 to April 2022). 

The mean temperature was close to the normal during the summer except in March 2022, which  recorded slightly above normal values. 

There was a delay in the onset of the cyclone season 2021-2022 as the first storm was named in  the third week of January 2022. In all, thirteen named storms were observed in the South West  Indian Ocean during this summer including Vernon which was named in the Australian region of  responsibility and later moved in the South West Indian Ocean. Out of these named systems, five  were intense tropical cyclones, two were severe tropical storm, five were moderate tropical storms and one was a subtropical depression. Two tropical systems crossed to the North of Mauritius in February 2022; Batsirai and Emnati. Both systems influenced weather over Mauritius and  Rodrigues and cyclone warning bulletins were issued for both islands.  

 

4.0 Conclusions 

Based on analysis of both linear regression models of the meteorological and oceanic parameters  that drive our climate in the southwest Indian Ocean and climate forecast from various model  products from Global Producers of Long-Range Forecast, the most likely outlook for winter 2022  is as follows: 

i. Observed trends of meteorological parameters in the region indicate that the onset of  winter 2022 will be during the first half of May

ii. Winter 2022 rainfall over Mauritius is expected to be close to normal. The cumulative  rainfall will be around 655 mm. Most of the rains will be concentrated mainly over the  Central Plateau, to the East and the South

iii. Rainfall over Rodrigues is expected to be slightly below normal in the first half of winter  and slightly above normal in the second half. The cumulative rainfall for Winter 2022 is  expected to be close to normal, amounting to 410 mm 

iv. The mean day maximum and mean night minimum temperature will be close to the normal. Temperature during the day will be around 23 degrees Celsius over the high grounds and  25 degrees Celsius along the coastal regions. The night temperature will around 16  degrees Celsius over the central plateau and around 18 degrees Celsius along coastal  regions. In Rodrigues, temperature during the day will be around 24 degrees Celsius over the high grounds and 27 degrees Celsius along the coastal regions. The night temperature  will be around 16 degrees Celsius over the high grounds and will be around 20 degrees  Celsius along coastal regions. 

When the Mascarenes will be under the influence of strong anticyclones, the Islands may  experience day temperatures to drop by 2 degrees Celsius or more below normal.

On few occasions, especially due to clear sky and calm wind condition at night, it is likely  that the minimum temperature may drop to 9 degrees Celsius in certain places in Mauritius. Minimum temperature over Rodrigues may drop to 13 degrees Celsius over the high  grounds.

Table 1 and Table 2 show the forecast of monthly average maximum and minimum  temperatures over different regions in Mauritius and Rodrigues respectively. 

Table 1: Expected monthly average maximum and minimum temperatures (in degrees  Celsius) over Mauritius.

 

 

Table 2: Expected monthly average maximum and minimum temperatures (in degrees  Celsius) over Rodrigues. 

 

v. Inference to other parameters  

a. Wind will blow mainly from the East South East with an average speed varying between 25 and 35 km/h. During the peak winter months mainly in July and August,  the passage of strong anticyclones to the south of the Indian Ocean may cause  strong pressure gradient over the Mascarenes, resulting in wind gusts that may  peak to above 90 km/h in the exposed areas; 

b. On certain occasions, the sea will become very rough with heavy swells generated  by the combined effect of travelling extratropical deep lows and strong anticyclones  to the south of the Mascarenes. The breaking waves are likely to reach the southern  and western shores of Mauritius and Rodrigues and may at times cause tidal surge  leading to temporary inundation of low-lying coastal areas; and 

c. The sixth assessment report from Intergovernmental Panel on Climate Change  (IPCC AR6 WGI) states the following: it is an “established fact” that human-caused  greenhouse gas emissions have “led to an increased frequency and/or intensity of  some weather and climate extremes since pre-industrial times”. Consequently,  extreme weather events including moderate to heavy showers, significant variation  in temperatures and strong wind conditions are very likely to occur over Mauritius and Rodrigues during winter 2022. 

This report will be updated upon availability of fresh information.  

 

Meteorological Services  

St Paul Road,  

Vacoas  

Date: 14 May 2022