This feature was first published in June 2025 in My Mensa Weekly, our exclusive newsletter for Mensa members. Find out more about becoming a Mensa member here.
Words: Andrew Cattanach
Over a single weekend in May [2025], more than 29 tornadoes ripped through the American Midwest, leaving at least 25 people dead. These dramatic weather events, with their iconic funnel clouds stretching from sky to ground, are both awe-inspiring and devastating. They’ve captivated public imagination for decades, becoming the subjects of documentaries and disaster films. But what truly drives these violent storms? Can technology help us better predict or understand them? Are they becoming more frequent as the climate changes? And what about the UK and Ireland – are tornadoes part of our weather story too?
What exactly is a tornado?
Although there’s some debate about what counts as tornadic activity, this article focuses on the dramatic kind familiar from news reports and films – like those that swept through the US Midwest this May. Most scientists agree these tornadoes typically form within a specific type of thunderstorm known as a supercell. Supercells arise when warm, moist air near the ground collides with colder, drier air higher up. This clash creates atmospheric instability that spawns towering cumulonimbus clouds and whipping winds. The warm air rises quickly in a tight column and, when combined with changes in wind speed and direction at different heights (a phenomenon known as wind shear), the air can begin to rotate.
Interestingly, tornadoes don’t always descend from clouds, as popular imagery suggests. Research shows that many form near the ground and build upward. They vary enormously in shape, size and duration – some are only a few metres wide and last seconds, while others stretch over a mile and persist for hours. While some cause catastrophic destruction, most are relatively weak and short-lived.
How strong are they?
Tornado intensity is usually measured using the Fujita scale, which ranks them based on the damage they inflict. The most powerful tornadoes have reached the top of that scale, with estimated wind speeds exceeding 300km/h. Some have killed hundreds of people, carved paths over 100 kilometres long and caused extensive damage to buildings and infrastructure.
These whirling nightmares can occur almost anywhere in the world, but North America experiences more than any other continent on Earth. The most violent ones – capable of flattening entire towns – occur overwhelmingly in the US, with rare but notable events in countries such as Bangladesh and, to a lesser extent, Canada. In the US, a unique blend of geography and climate creates ideal tornado-forming conditions, although the precise reasons are still not fully understood.
One hotspot is ‘Tornado Alley’, a region in the central US particularly prone to severe outbreaks. During spring and summer, warm and humid air from the Gulf of Mexico collides with cool, dry air from Canada, setting the stage for supercell formation and potentially long-lived, destructive tornadoes.
Tracking the storm
Tornadoes are closely studied by scientists around the world, including Dr Jana Houser, an associate professor at The Ohio State University and a leading figure in the field. Early in her career, she even contributed to the research behind the 1990s’ blockbuster Twister. Like many meteorologists, Houser relies on radar to monitor and analyse how storms develop. These systems not only help researchers understand tornado behaviour but also play a vital role in alerting the public when danger is approaching.
New technologies are expanding what researchers can observe. Drones are now being used to approach storms more closely than humans safely can, gathering data from within the tornado itself – such as wind speed, pressure and near-surface temperature gradients. Artificial intelligence is also transforming the field by helping meteorologists sift through vast datasets to better understand the conditions that give rise to tornadoes and to improve forecasting accuracy.
Still unpredictable
And that’s the challenge: while scientists understand that most tornadoes form from supercell storms – and they have a strong grasp of the general mechanics – they still can’t predict exactly when or where one will appear. Even with modern warning systems, alerts can sometimes arrive too late for people to take cover. Meteorologists are getting better at spotting the broader conditions that favour tornado formation, often issuing ‘tornado watches’ to warn the public that the ingredients are in place, even if a tornado hasn’t yet formed.
But what makes one supercell produce a tornado and another fizzle out? That part is still murky. “We’re learning more and more that those differences are very small scale,” says Houser. “They have to do with storms colliding with each other, things like the terrain – the lay of the land, where there are rivers or valleys. Even things like surface roughness – areas of forest next to grassland. All these things not directly related to climate.”
In the US Midwest earlier this month, those small, unpredictable differences played out in real time. Tornado watches were issued ahead of the storms, giving some communities crucial minutes to prepare. But the systems intensified quickly, and many were caught off guard – a stark reminder of just how elusive tornado prediction still is.
A changing climate?
Whether tornadoes are becoming more frequent due to climate change is a complex and still unresolved question. Some researchers believe that shifting weather patterns will make tornado-favourable conditions more likely in certain regions. So far, though, the overall number of tornadoes each year hasn’t significantly changed.
What has changed is their distribution: tornadoes are now occurring over fewer days, but often in more intense clusters. There is also evidence that the US’s traditional ‘Tornado Alley’ is shifting slowly eastward, possibly due to warming in the Gulf of Mexico, which provides much of the warm, moist air that fuels these storms.
Our quiet twisters
Believe it or not, the UK experiences around 30 tornadoes each year – more per square mile than any other country. These are usually small and short-lived, but they can still cause notable damage. In Ireland, meanwhile, around 10 tornadoes are reported every year; these tend to be ‘mini-tornadoes’ though can still be potentially dangerous.
Incidentally, Ireland’s first reported tornado was in County Westmeath on 30 April 1054, as documented in the medieval Irish chronicle, Chronicon Scotorum.
So, while we may not see the dramatic twisters of America’s Midwest, it’s not entirely off the tornado map – and as weather patterns shift, it may pay to keep a closer eye on the skies.
Explore the science of the storm
Dive deeper into cutting-edge research, storm-chasing tech and expert insights on the US’s National Severe Storms Laboratory website.
Image credit: Shutterstock
