Tornadoes also regularly rage across Europe, but 'chance of a severe one remains small'
When a tornado makes the news, it often has caused damage somewhere in the US. But they also occur regularly in Europe. In the past ten years, an average of about 380 tornadoes per year have been recorded in Europe, including Russia, says meteorologist Pieter Groenemeijer. He is an expert in extreme weather affiliated with the European Severe Storms Laboratory (ESSL).
Yesterday afternoon, a tornado reduced the small village of Pomas in southern France to rubble in a few minutes. Based on footage, Groenemeijer estimates that the tornado had a strength of IF2 to IF3, with wind speeds between 200 and 300 kilometers per hour. "A few times a year tornadoes of this strength occur in Europe," he says.
Tornadoes are observed relatively often especially in areas around the Mediterranean Sea. In France alone, an average of about thirty tornadoes are recorded annually. Of these, about three have a strength of IF2 or higher. On the Fujita scale, IF5 is the strongest category, with wind speeds up to approximately 500 kilometers per hour.
The conditions for a tornado were favorable yesterday. "A lot of warm and humid air moved inland from the Mediterranean Sea," says Groenemeijer. That air formed the ideal breeding ground for a supercell, a powerful thunderstorm with a rotating upward air current from which tornadoes can develop.
The tornado that passed over Pomas yesterday was caused by such a supercell. A lot of energy is needed in the lower layers of the atmosphere for its formation. Wind conditions are also crucial. "How hard the wind blows and how strongly it increases with height partly determines whether a thunderstorm will rotate and eventually form a tornado."
A strong tornado is often accompanied by severe thunderstorm activity. Tornadoes that arise from supercells often produce a lot of lightning. "Sometimes we see one lightning flash per second or more. That is due to all the energy released in the storm."
Also, in a strip from northwest France through Belgium to the Netherlands, tornadoes occur relatively often, says Groenemeijer. Warm, humid air regularly collides with cooler air there. In combination with favorable wind conditions, tornadoes can form here.
Severe wind gusts
Next Thursday and Friday there is a chance of strong thunderstorms in the Netherlands. That does not automatically mean tornadoes will form. That depends on many different factors, including wind conditions. It is difficult to predict how these will develop. "The chance of such strong tornadoes as in France is relatively small."
The tornado in southern France caused a lot of damage:
Even computer models have difficulty predicting tornadoes. They can indicate where the chance of severe thunderstorms is high, but it is much more difficult to predict how such a storm will develop afterwards. It can also result in other dangerous weather, such as severe wind gusts.
More photos and videos
Whether tornadoes occur more often due to climate change is difficult to determine according to Groenemeijer. This is because in the past far fewer observations of dangerous weather were collected than now.
"If you look at the number of recorded tornadoes between 1980 and 1990 and compare that with the past ten years, you see much higher numbers in recent data," he says. "But that does not automatically mean there are more tornadoes."
According to Groenemeijer, this is because nowadays many more people have smartphones and take and share photos and videos, resulting in more reports.
A warmer climate can lead to conditions favorable for severe thunderstorms. Research by the ESSL shows, for example, that conditions for severe hailstorms have clearly increased, especially in the Alpine region.
The Netherlands has also experienced a tornado of the strongest category. In 1927, an IF5 tornado passed over the Achterhoek. "It turned newly built houses into piles of bricks," says Groenemeijer.
As many walls as possible
There is little that can be done against a tornado of that strength. "The most important thing is to have as many walls as possible between yourself and the tornado and at least stay away from windows. A basement is therefore the safest place."
Groenemeijer emphasizes that a tornado of this strength is very rare. "We should not forget that. Waterspouts, a kind of tornado over the sea, occur much more often."
People often try to film tornadoes, but that carries risks, Groenemeijer warns. "If the tornado comes closer, you can be in danger. Always think first and foremost about your own safety."
During the thunderstorms that passed over the coastal provinces last week, a waterspout was seen over the North Sea: