SmilingSouth

Strong winds followed by snow in high-lying areas of the Eastern Cape from Friday, predicts the SOUTH AFRICAN WEATHER SERVICE

An intense cold front associated with a steep upper-air trough, currently developing over the western Atlantic Ocean, will affect the western parts of the country on Thursday and Friday, spreading to the southern and central parts on Saturday. Rainy and very cold conditions with snow on the high-lying areas will set in over the western parts of the Western Cape from Thursday afternoon, 26 August 2021, spreading to the western and southern parts of the Northern Cape and the remainder of the Western Cape overnight into Friday, 27 August 2021.

Figure 1: Satellite image for Tuesday, 24 August 2021, indicating the approaching cold front, located over the western Atlantic Ocean. Source: Eumetsat (2021).

Following a fairly settled week for the western parts of the country, a cold front together with an associated upper-air trough is expected to affect the Western Cape and Northern Cape, mainly from Thursday afternoon through to Saturday. At the same time, this weather system will encroach eastwards into the Eastern Cape province from Friday afternoon as well as the central interior of South Africa, including KwaZulu-Natal on Saturday, 28 August 2021.

Widespread rainfall will set in over the western parts of the Western Cape on Thursday afternoon, spreading to the western and southern parts of the Northern Cape overnight. Rainfall accumulations of 20 to 30 mm can be expected, with heavier falls, of the order of 40 to 50 mm expected over the south-western Cape (refer Figure 2). This rainfall may lead to localised flooding of informal settlements. Moreover, such flooding may also pose a distinct risk to safe driving on major roads. Motorists driving under such conditions are advised to reduce speed (especially under conditions of reduced or impaired visibility) and to observe safe following distances.

Figure 2: 24-hour rainfall accumulation in mm for Thursday (left) and Friday (right). Source: GFS model provided by NOAA (National Oceanic and Atmospheric Administration)

Figure 3: Predicted maximum temperatures for Friday (left) and Saturday (right). Source: GFS model provided by NOAA (National Oceanic and Atmospheric Administration)

Very cold conditions are expected from Friday (refer Figure 3) over the south-western quadrant of the country, spreading to include much of the southern and central interior regions of South Africa by Saturday, 28 August 2021.

Snowfall is expected over the high-lying areas of the Western Cape and the southern and western high- lying areas of the Northern Cape, mainly from Friday spreading to the high-lying areas of the Eastern Cape and the Drakensberg region of KwaZulu-Natal during Saturday. Significant lowering of local atmospheric freezing levels is anticipated over the aforementioned areas, allowing for disruptive snowfall in some places. This may result in the closure of some mountain passes and cause traffic disruptions. Small stock farmers are advised to move their smaller livestock to shelter at an early stage to mitigate losses, ahead of the arrival of the winter weather.

Prior to landfall of the approaching cold front, strong winds (40 to 60 km/h) are likely to occur over parts of the interior of South Africa. Such strong, gusty winds may cause difficulties for high-sided vehicles along major routes, especially over the interior of the Western Cape, the interior of the Eastern Cape, the Northern Cape, western Free State and the western parts of the North West province from Thursday into Friday. In addition, the public are urged to exercise caution and to refrain from lighting fires in the open and/ or discarding lit cigarettes or matches. The combination of strong, gusty winds and abundant fuel (in the form of dry, frost-affected grass and brush) is likely to promote conditions conducive to the rapid ignition and spreading of veld fires, ahead of the cold front.

The South African Weather Service will issue a further media release later this week, to provide greater detail regarding this rapidly developing weather system (such as when and where the more significant snowfalls can be anticipated). The accuracy of predictions provided by numeric weather prediction (NWP) models typically improves significantly as the lead-time shortens. SAWS therefore urge the public to be circumspect when considering long lead-time weather predictions from unproven and irregular sources. Such products are typically designed to cause panic, rather than to advise and inform.

The South African Weather Service will continue to monitor any further developments relating to this weather system and will issue subsequent updates as required. Furthermore, the public are urged and encouraged to regularly follow weather forecasts on television and radio. Updated information in this regard will regularly be available at www.weathersa.co.za as well as via the SA Weather Service Twitter account @SAWeatherServic

Compiled by Wayne Venter and edited by Kevin Rae.

• This is an unedited media release from the South African Weather Service on 24 August 2021.