Zaine Perry

They rage across the ocean, tear through coastlines, and leave devastation in their wake but tropical cyclones (TCs), for all their fury, are surprisingly delicate creatures. They rely on a perfect mix of conditions to form, survive, intensify and when just one of those ingredients goes missing, the whole system can collapse. That’s what makes them so fascinating (and so difficult to predict).

Hi, I’m a 2^nd year MSc student studying at the University of Cape Town (UCT), trying to understand one of the strangest TCs ever recorded: TC Freddy. I use numerical models to see how storms like Freddy form, move, intensify and impact regions over the South West Indian Ocean to improve forecasting and better protect vulnerable communities. I first encountered this storm – or at least the early parts of it – during my Honours in Ocean and Atmosphere Science at UCT, around two years ago.

Freddy formed northwest of Australia on 6 February 2023 and went on to travel over 8 000 km across the southern Indian Ocean, lasting until 14 March – over a month later. It made its first landfall in Madagascar on 21 February 2023 and went onto cross Mozambique a few days later. It brought catastrophic flooding, damages and death across Madagascar, Mozambique, and Malawi, and is now remembered as one of the most intense and persistent cyclones ever recorded in the region.

What I didn’t expect, however, was how familiar Freddy would become to me.

At the time, Freddy had recently occurred and gained a lot of attention for its unusual behaviour. My supervisors flagged it as a system worth looking into for my Honours research. Little did I know I’d still be talking about Freddy in my MSc thesis, still trying to make sense of what kept it alive for so long. It’s almost like Freddy refused to go quietly, both in the atmosphere and in my academic life.

Its record-breaking lifespan caught the attention of many in the scientific community, with researchers across the globe working to understand how a single storm could last so long. My work is one contribution to this wider effort. Here is my 2 cents worth.

At first glance, Freddy had the basics of a TC: warm sea surface temperatures and relatively low wind shear, the kind of ingredients researchers usually expect when a storm spins up. However, as I dug deeper into the data, I realised there was so much more going on and some of it was hiding beneath the surface.

One of the biggest surprises was ocean heat content (OHC). Freddy’s track overlapped with areas of high OHC, which I like to think of as the ocean’s energy reserve for fuelling storms. The friendly petrol attendant at the Engine garage, if you will. That hidden warmth beneath the surface gave Freddy the energy to keep going, even when you’d think it would start running low.

Another curveball was the influence of TC Dingani – a separate system swirling to the west of Freddy in mid-February 2023. On paper, the two storms were far apart, but they ended up indirectly shaping each other’s paths. Dingani interacted with the Mascarene High, a major subtropical pressure system, splitting it into two separate high-pressure cells. This split Mascarene High, altered the steering flow in the region and helped push Freddy westward, right across the southern Indian Ocean and into Madagascar.

Even more fascinating was the role of moisture. Dingani may have helped funnel moisture toward Freddy, effectively feeding it from a distance. Moisture is the lifeblood of a TC, and Freddy managed to maintain a rich supply throughout most of its journey by getting a blood transfusion from the guest to the west (Dingani). Weather data showed strong moisture fluxes from the lower and middle atmosphere, particularly in the lead-up to landfall events.

Speaking of landfalls, did you know that only 5% of TCs that reach Madagascar go on to make landfall in Mozambique? Freddy didn’t just make landfall, it did so twice with a “ping-pong” motion in between. After crossing Madagascar, Freddy moved into the Mozambique Channel, weakened overland, re-emerged over warm waters, and then re-intensified. That kind of behaviour isn’t unheard of, but it’s certainly unusual and hard to do numerical modelling on, especially when storms interact with both land and ocean environments in such complex ways.

In fact, modelling Freddy was one of the biggest challenges researchers faced. Weather models struggled to simulate its intensity and track with much accuracy. Even widely used datasets like IBTrACS, used by researchers and disaster agencies, missed parts of Freddy’s path, especially when it weakened over land. This is a big problem for studies that look at where storms go and what damage they cause, particularly in parts of southeastern Africa. These kinds of studies help us understand how often communities are hit, how severe the impacts are, and where support may be needed most. If the data says the cyclone wasn’t there… well, good luck claiming from insurance for the damage it caused. No track, no storm. No storm, no support. For vulnerable communities, that missing data can mean missing out on recovery aid they desperately need.

So, what does Freddy teach us?

For one, it shows that TCs are fragile beasts, sensitive to a range of atmospheric and oceanic conditions, many of which change from day to day. They’re not just wind and rain; they’re dynamic systems shaped by pressure patterns, ocean eddies, moisture transport, and even the presence of other storms.

Most weather models only simulate the atmosphere, but Freddy’s case suggests that leaving out the ocean, especially things like OHC, can be a big oversight. To better understand storms like Freddy, researchers need better tracking algorithms, more detailed ocean data, and coupled models that can simulate the feedback between ocean and atmosphere in real time. Only then can we improve our forecasting and give vulnerable communities the information they need before the next Freddy arrives.

Until then, I’ll probably still be thinking (and talking) about Freddy because some storms just leave a mark that’s hard to shake.

This map shows how large-scale pressure systems helped steer Cyclone Freddy (dots) and Dingani (triangles) across the Indian Ocean. Think of it as the atmospheric ‘roadmap’ that guided their paths (Perry et al., 2024).

Elizabeth Carr

Every Saturday morning across South Africa, thousands of people voluntarily wake up early to put on shoes that they have overpaid for and jog through public parks and green spaces, pretending it’s fun. I should know, I’m one of them. I am also a parkrun volunteer (read: unpaid local hero), which means I’ve scanned thousands of finishing tokens and have often been sprayed with a light mist of someone’s sweat as they huff up to me and hand over their sweaty, crumpled runner ID which I then have to delicately unfold and scan.

But recently, for me at least, there’s something about running in a South African summer that feels different lately. Not emotionally but rather physically, specifically, hot. Like, why-is-my-sweat-sweating? hot. Like, why-are-my-shoes-melting-to-the-payment? hot. Breathing feels less like drawing in fresh morning air and more like sipping liquid lava through your nostrils.

It’s not just me. I’m currently pursuing a postgraduate degree (MSc) where I am researching the risk of heat stress in parkrun, I’m also an avid parkrun runner and long-time volunteer. Tragically, during one of the events I was volunteering at last year, an elderly gentleman passed away. He was a regular who had completed over 250 parkruns and I saw him and his wife every Saturday morning at the parkrun. His passing deeply affected me, not only because it was such a shock, but because it left me with unanswered questions: why then and why there? I later realised that heat stress may have potentially played a role in what had happened. That moment sparked my obsession with understanding how rising temperatures affects casual exercisers, people who show up to move, not compete.

My research led me to the literature, where what I found made me sweat even more. Studies show that South Africa is warming at twice the global average, with more frequent and intense heatwaves recorded across the country. It’s not just a summer problem anymore, it’s become an all-year-round reality. These events fall into what scientists call extreme temperature events, things like heatwaves and warm spells. Extreme temperature events are one of the clearest signals that climate change is showing up on our doorstep. These hot spells don’t just make us sweaty and grumpy, they are known to affect everything including human health and productivity. So what’s the problem with a little heat while exercising? Well, quite a bit, actually. While there’s already research on the risks and effects of heat stress in professional sports and endurance events, far less is known about how heat affects casual exercisers, the kind of people who show up at parkrun with good intentions, sunscreen and maybe a slight hangover. Parkrun is unique: it’s free, inclusive, non-competitive, and attracts a wide range of people, many of whom aren’t trained athletes. That’s exactly why I chose to focus my research here. I’m still early in the process, but I’m hoping my work will help fill this gap in the literature and raise awareness about the heat-related risks faced by everyday South Africans who are just trying to stay active and healthy.

When your body’s core temperature rises (like when you start jogging because you cannot let someone five age categories above you beat you), your heart has to work harder to keep you cool. Blood is rerouted to your skin to help with sweating, meaning less oxygen-rich blood reaches your muscles. That’s why hot weather runs feel harder (and more dangerous) than cool ones.

This is called heat stress, and it’s no joke, even for casual exercisers trying to avoid the label “couch potato”. While professional athletes often have trainers and professionals to help them manage it, the average parkrun runner is armed with nothing more than a cap from Mr Price Sport and half a bottle of warm water in a reused Energade bottle.

Still, we show up, why? Because parkrun is more than a Saturday 5km. It’s community. It’s routine. It’s a chance to say “Howzit!” to that one Tannie who finishes every run-in jeans. But showing up may start doing more harm than good, unless we start paying attention to what heat does to our bodies. It is time we acknowledge that heat is no longer just uncomfortable. It is a real hazard, even during recreational exercise.  

So what can we do?

As a volunteer, I’ve started noticing more runners slowing down or walking the route when it’s hot. That’s smart. The human body isn’t designed to set a PB (Personal Best) in high temperatures. Hydration, shade, looser clothing and adjusting your pace are all small but crucial steps. Maybe also encouraging parkrun SA HQ to move start times earlier in some locations, because let’s be honest, 8 a.m. in Durban in summer is less “casual morning jog” and more “voluntary, free sauna session”.

Beyond personal strategies, this is a public health conversation. We need city planners to consider green spaces and shade infrastructure. We need schools and sports organisations to revise heat policies. We need awareness campaigns that make people take heat as seriously as they take sunscreen on Clifton beach in peak Dezemba .

We also need to start talking about heat stress in a way that people understand, because let’s be honest “heat exhaustion” doesn’t sound life-threatening. But if you say, “You could pass out mid-run and wake up with a medic feeding you ice chips while your brain feels like pizza that has been warmed up in the microwave”, that tends to get people’s attention.

So whether you’re a casual jogger, a volunteer saint or just someone who sweats from the head down whenever the summer temperatures start to approach, remember this: climate change isn’t some far-off thing happening to polar bears. It’s happening right here, on the running paths, the school fields and the pavements outside your local coffee spot.

Until someone figures out how to run a parkrun inside a Woolies freezer aisle, maybe take the hint: slow down and cool off.