Picture: for illustration purposes

Western Cape Experiences Historical Rainfall Over Heritage Day Weekend

Published September 29, 2023
9 months ago

Mother nature spared no effort in reiterating her might over the Heritage Day weekend causing Western Cape to bear witness to one of the intense rain spells in recent history. Destruction was widespread; roofs were torn off, streets flooded, and entire communities isolated, as relentlessly stormy weather hammered the province.

The mammoth downpour was attributed to the presence of a persistent and vigorous 'cut-off low-pressure system,' an equatorward displacement of a low-pressure system at lofty altitudes. First noted on Saturday night, the system grew more menacing as Sunday approached, barraging the province with devastating wind, extreme rainfall, and tumultuous seas.

With the assistance of Dr Peter Johnston from the Climate System Analysis Group (CSAG) at the University of Cape Town and Kate Turner from the South African Weather Service (Saws), the details behind the Western Cape’s meteorological upheaval were unpacked. Their explanations indicated the forceful and all-encompassing nature of a cut-off low-pressure system—the cause of the weekend's precipitation pandemonium.

These systems are honeypots of moisture, developing in the upper atmosphere where they generate showers and thundershowers. Their severity depends on their height in the atmosphere, hence the more elevated the system, the higher the likelihood of intense rainfall. The system experienced over the Heritage Day weekend was rather deep and essentially became a sponge accumulating moisture from the ocean, thus resulting in prolonged rainfall across the Western Cape.

While this perverse downpour's intensity was unusual over the weekend, these weather systems are actually common in South Africa, particularly during the changeover seasons of spring and autumn. Turner confirmed that the Cape Winelands and Stellenbosch received an astonishing 193mm of rain over two days, while the City of Cape Town was not far behind, tallying 143mm of rainfall.

Albeit such an isolated and violent weather system was unique and arguably unparalleled in the past decade, multitudes of these cut-off low-pressure systems have been the norm. However, attributing these occurrences directly to climate change remains a complex task. Scientists continue to monitor weather patterns and systems, with the understanding that rising global temperatures contribute to increased atmospheric moisture and more frequent and intense rainfall events.

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