South Africa’s winter rainfall zone and its future outlook

September typically marks the end of South Africa’s winter rainfall season, which generally starts in April and is uniquely experienced across the country’s southwestern Cape and western coast, a region referred to as the winter rainfall zone. Much of this winter period rainfall is produced by cold front arms of mid-latitude cyclones deriving moisture from westerly winds and originating in the southwest Atlantic Ocean, just off the coast of Argentina.

Research shows that the winter period rainfall regimes and characteristics of associated weather systems are changing and will continue to do so as a result of human-induced climate change – negatively impacting surface water resources and agricultural activities across the winter rainfall zone. Due to global warming trends, the westerly winds are migrating poleward, which in turn is among the drivers of a trend towards drier conditions during the April-September winter period. Despite a somewhat wetter than normal month in June 2022, with some flooding in the southwestern Cape, rainfall index maps from the May-July 2022 editions of the Agricultural Research Council’s Umlindi Newsletter (https://www.arc.agric.za/arc-iscw/Pages/News-Articles.aspx) suggest that drying trends are already manifesting as the winter rainfall region has experienced slightly drier than normal conditions, particularly during the April-May months. This is similar to what happened during the so-called “Day Zero” drought period from 2015-2017, which was consistently characterized by drier than normal conditions during the early winter months. As for the rest of the 2022 winter season, forecasts from the South African Weather Service suggest drier than normal conditions are likely.The full article is for subscribed members only. To view the full article please subscribe. It’s FREE!Log In Register