A low- and high-pressure system may converge over South Africa this weekend, and where these systems meet, unstable weather conditions and heavy rainfall are likely.
By Alani Janeke, senior journalist at African Farming and Landbouweekblad
The drier conditions currently seen over parts of the summer rainfall region may be short-lived, especially across the summer grain areas and surrounding parts.
Weather models indicate that around 14 November, a low-pressure system over Namibia, the western parts of Botswana and the Northern Cape will strengthen, drawing tropical moisture south-eastwards over the country.
At the same time, a strong high-pressure system located west of the country will move eastwards around the Western Cape. This will cause cold air from the south to move northwards between 15 and 17 November, where it will meet the warm, humid tropical air.
Possible Flooding
“It is in this area, where the two air masses converge, that heavy rain and very unstable weather conditions are expected,” says independent agricultural meteorologist Johan van den Berg. “Current forecasts show that especially parts of Gauteng, the eastern North West, western Mpumalanga, northern and eastern Free State, and parts of Lesotho could receive more than 50 mm of rain on Saturday, Sunday and Monday, 15, 16 and 17 November.
“There is a strong likelihood of flooding around Sunday, 16 November – particularly in Gauteng – with more than 50 mm of rain expected in a single day.”
The current development of the La Niña phenomenon, along with sea surface temperatures in the Indian Ocean, which are highly favourable for rainfall, are the main underlying drivers of the expected above-average rainfall in the coming weeks and months, van den Berg says.
Also read: Frequent summer showers forecast from 14 to 25 November
Rainy Weather May Delay Planting
This weather may hamper summer grain planting, particularly in areas where soils are already saturated. “From around 14 November into December, cloudy and rainy conditions are likely on most days. This could result in significant planting delays, especially in the eastern parts of the country, where planting has not yet been completed and may no longer fall within the optimal planting window, Van den Berg says.
Also watch: Bakkie washes away as rain brings relief for some Northern Cape farmers
Conditions in Other Parts of the Country
As for the rest of the country, Van den Berg says rainfall will mainly occur north of the Drakensberg, meaning that the Eastern Cape, which has received little rain recently, is also likely to see very little over the coming weeks.
The chances of rain over the south-western Northern Cape and Western Cape remain very low.
A high-pressure system will influence the south-western and southern parts of the country, bringing little to no rain and very hot conditions.
Meanwhile, very high temperatures and heatwave conditions are expected until about 25 November across the western Northern Cape and large parts of the Western Cape, particularly along the West Coast and in the Winelands district.
