CAPE TOWN, SOUTH AFRICA - APRIL 07: At least 9 properties were destroyed or badly damaged in the Sunny Cove area in Fish Hoek by a out of control fire on April 07, 2024 in Cape Town, South Africa. The South African Weather Service (SAWS) issued a warning of a rare weather occurrence that is set to disrupt coastal areas along South Africa's south-west to south-east coastline. (Photo by Brenton Geach/Gallo Images via Getty Images)
Strong winds and heavy rainfall continued to lash the Western Cape on Monday and are set to continue until Tuesday, according to the South African Weather Service (SAWS).
The damaging winds fuelled fires, uprooted trees, ripped off roofs, forced road closures and triggered school closures on Monday in the Cape Winelands, Helderberg and Overberg districts. On Saturday, the SAWS issued level 9 weather warnings (out of 10) for the province.
Fire gutted the 300-year-old Manor House at Blaauwklippen Vineyards outside Stellenbosch, while strong winds damaged roof structures at the Stellenbosch Medi-Clinic. The Somerset Mall was closed after its roof sheeting was blown off and Chapman’s Peak Drive was closed to traffic because of high winds and threats of rockfalls.
“Our teams across this province will be dealing with the closing of roads to remove danger, so please if you are travelling, try and avoid areas that can be flooded,” Western Cape premier Alan Winde said during a briefing at the disaster management centre in Tygerberg on Monday.
“We need to be safe out there, that’s my message … We have got flooding in some parts of the Overberg, the Buffelsjagand low-level bridge in Swellendam, so localised flooding, nothing major at the moment but the rain is falling and we say to the people make sure that you are safe, don’t take any chances in any of the low-lying areas.”
Cut-off low
Kanyisa Makubalo, a forecaster at the SAWS Cape Town office, said a cut-off low-pressure weather system dominated the weekend into Monday for the western parts of the country.
“This weather system develops in the upper air as it cuts off from its normal westerly flow. It can be associated with weather systems that develop at the surface or lower levels of the atmosphere making it more potent, as in this case,” Makubalo said.
The combination of the upper air and surface weather systems resulted in very tight wind gradients, especially over the south-western parts of the Western Cape. Tight gradients lead to very strong winds, as was the case this weekend, Makubalo said.
“We advise that people stay safe by adhering to warnings, and restrict travel as much as possible, taking safety precautions when driving and listening to disaster managers’ instructions to safety.”
‘Not abnormal’
This type of weather is normal for this time of year for the Western Cape, said Neville Sweijd, the director of the Alliance for Collaboration on Climate and Earth Systems Science in the province.
“We usually get a big storm in April around Easter,” he said. “The particular system is a little unusual, it’s a cut-off low; but these are not uncommon in the shoulder seasons.”
The shoulder season is roughly March to April, early May in some places, and September to October and early November in other areas.
“There were very strong winds in the Western Cape and that caused damage. These windstorms are usual and they precede the rain. But because it came before the rain it set off fires, some maybe set intentionally. Strong winds precede the cut-off low or other systems and if it has been dry, it’s vulnerable to fire.”
Sweijd added: “Records of floods in the Southern Cape and Overberg often happen in the shoulder season. Often the strong winds after a dry hot summer cause floods.”
He said that there was a big cut-off low system in August/September last year. “The questions to ask is how often are these systems making landfall and are they happening more often? The trends are important so how often, how severe and are they more energetic” needs to be studied.
Build better for a more extreme future
The trends that must be checked are frequency, intensity and duration and “that is what we’re keeping track of”, he said.
“The IPCC [Intergovernmental Panel on Climate Change] says this is a key manifestation of climate change — the intensity, frequency, strength and so forth are trending upwards … If they happen more often, it will make it more damaging.
“It’s critical to note that not only the government has to do stuff to deal with the problem, but people also have to fix their roofs, build the roofs appropriately for high winds, create gutters, cut trees down so they don’t get too heavy, trim them back as lots of people do to prepare for winter anyway.
“And of course, infrastructure has to be designed so that it can withstand extreme events, and they are generally designed to withstand what we call 1-in-50-year events, so things that are very big, but are rare, we still have to be able to withstand that.”
The problem is that with climate change, the intensity of these extreme events is more frequent and more severe, which means that those designs are no longer suitable for the changing climate, Sweijd added.
It’s very difficult for governments to be able to “absolutely plan” in advance, he said, adding: “The best thing they can do is communicate, which is what they are doing. So, I think they are quite successful in dealing with it. But how to prevent damage is very difficult to say.”
“Rivers come down once in 100 years, the people forget and they build in harm’s way. And that’s generally the problem — infrastructure and private property are built in harm’s way. The best thing to do is to regulate where people can build. But that often is lost in memory.”