Localised flooding and landslides caused by heavy downpours in KwaZulu-Natal over the past days have led to fatalities, significant damage to infrastructure and power outages.
READ: Rescue teams deployed as flooding rocks KwaZulu-Natal
The South African Weather Service (SAWS) released a statement explaining what caused the heavy rain, and warned that though the rainfall should weaken throughout the province on Wednesday, 13 April, more rain is expected over the weekend.
‘Whilst impact-based warnings were indeed issued in a timely manner by the SAWS, it appears that the exceptionally heavy rainfall overnight and this morning exceeded even the expectations of the southern African meteorological community at large,’ the SAWS said.
‘Overnight rainfall reports from KwaZulu-Natal have underscored the particularly heavy and extreme nature of the rainfall, with some 24-hour falls exceeding 200 mm. More noteworthy, is that a few stations even reported 300 mm or more! A selection of the highest overnight rainfall measured in KwaZulu-Natal includes King Shaka International Airport (225 mm), Margate (311 mm), Mount Edgecombe (307 mm), Port Edward (188 mm) as well as Virginia airport (Durban north) with 304 mm.
‘Such rainfall is of the order of values normally associated with tropical cyclones; however, SAWS must strongly emphasise that this system is not tropical in nature, nor is it a tropical cyclone.
‘The good news is that, by tomorrow [Wednesday] the current rainfall system will have weakened considerably, heralding a spell of a few days of settled dry weather. However, the public should take note that rain is expected to return to many of our provinces, ahead of and during the coming Easter weekend, when many people will be travelling to other parts of the country.
‘The public is therefore urged to continue to monitor forecasts and warnings issued by SAWS. A dedicated media release, covering the weather forecast for the Easter weekend, will be issued by SAWS soon.’
What was the reason for the heavy rain?
‘In short, a cut-off low in the upper reaches of the troposphere is currently moving seawards, off the eastern coast of South Africa. Cut-off lows are associated with widespread instability in the atmosphere, which can promote periods of prolonged rainfall, as witnessed over many of the interior provinces of South Africa at the weekend.
‘For KwaZulu-Natal however, the effect of the cut-off low system has been markedly enhanced by the presence of sustained low-level maritime air which has been fed in from the southern Indian ocean, thus driving the system to produce more rainfall. Moreover, the original source of the maritime air was from warmer, sub-tropical parts of the ocean, with a greater capacity to transport moisture, an essential ingredient of any rain-producing system.
Could this rain system be attributed to global warming and climate change?
‘No, as weather scientists we cannot attribute individual weather events occurring on short timescales to longer-term events, occurring over years or decades. However, notwithstanding the above, we can state with confidence that globally (as a direct result of global warming and associated climate change) all forms of severe and extreme weather (such as heatwaves, heavy rain, and coastal storm surge events) are becoming more frequent and more extreme than in the recent past.
‘In other words, heavy rain events such as the current incident can rightfully be expected to recur in the future and with increasing frequency.
The South African Weather Service will continue to monitor any further developments relating to this weather system and will issue subsequent updates as required. Updated information will regularly be available at www.weathersa.co.za.
Picture: Screenshot of video by Farmers Aid – SA
