Today, the term “supercell” comes up a lot when talking about the current weather in Europe. But how do we explain these storms as being more substantial and sometimes more destructive than usual?
What is a supercell thunderstorm?
Supercell storms are large-scale violent events that require several conditions to occur, explained IRM meteorologist Pascal Mormel. First, there must be a collision between masses of very warm air and cold air, creating an atmospheric instability that creates an updraft. Then, there must be a wind shear (author’s note. The difference in wind speed or direction between two sufficiently close points in the atmosphere). Heat and humidity also come into play.
All these elements are an explosive cocktail that creates “very violent storms.” Also, within a supercell, the cloud’s air mass is kept in circulation, forming a cyclone, which sometimes forms a hurricane. Belgium has already experienced this, in Buring in 2021, where more than 90 houses were affected and 10 were uninhabitable. Additionally, it could lead to “heavy hail and storms.”
The climate experienced by Europe made it particularly favorable for these supercells, which bear this name because of their enormous dimensions. Cold air from northern Europe met warm air from the south, resulting in many bad weather conditions in France, Slovenia or Italy.
Slovenia hit by historic floods (photos)
“Mediterranean gives extra energy to these storms”
In the coming days, many European countries will be severely affected by this weather phenomenon. But should we expect a recurrence of supercells? According to Pascal Mormel, he wants to be aware of the fluctuation of weather conditions and “the regression that determines whether the phenomenon is increasing”.
But there’s no denying that the heat Southern Europe is experiencing isn’t going to help: “We’re in a very good situation, which causes particularly powerful storms somewhere, including the reference storm, the supercell.”, he explains. “What’s a little scary about the very high temperatures we’re having this year is that the Mediterranean is particularly warm, adding to the phenomenon..”
Due to this, very heavy rain is likely to fall,” he said.Especially the areas around the Mediterranean like the Cevennes or the Pyrenees-Orientales”. The reason? The warm air moves to meet the mountains and then carries precipitation. This is known as the Sevens episode, which does not affect Belgium, but affects the Mediterranean interior.
Another point Pascal Mormel worries about is the power of a supercell storm: “They are long-lived, so they are thunderstorms that can sometimes produce very heavy rainfall..”
“What I feared a few days ago is confirmed”: Here is the weather forecast for the end of August
Belgium in danger?
According to the meteorologist, we can observe a significant increase in these occurrences in the last 30 to 40 years. “According to our statistics, we can still assume that it is not negligible. These intense rains associated with storm events mostly take place in summer,” he adds.
“It can also be said that a warmer atmosphere holds more water vapour. It doesn’t mean it will rain immediately, but when this water vapor reaches saturation point, it can cause more precipitation.”, Pascal Mormel develops.
However, it does not rain often, but instead: “We can estimate that the rain will be less, but when it does fall, it will be more intense. 1° of warming would lead to 8% more extreme precipitation.”
A meteorologist qualifies for flood risk. There are different floods. “Occasional floods are associated with very powerful storms or very severe storm skies. These are mostly floods. Like what happened on Friday, it will be a very short-lived event of a few tens of minutes”. Floods that are “most brutal in their intensity” unlike first floods, last longer but rise gradually. So short rains can lead to disastrous situations.
“Studies indicate that we often have periods of extreme drought, but that can be punctuated over time by brutally heavy rains that can cause major problems.”, concludes the meteorologist.
Weather: Belgium experienced its wettest and darkest July since 1936
Indian summer or early winter?
The meteorologist takes the question with tweezers. But “Nevertheless, there is a tendency to indicate with extreme caution that the first days or the next two to three weeks from Friday will be marked by generally favorable weather.”, he assures. We should not expect the end of the rain, but this weekend the temperature will rise to 24 degrees, and the moderate conditions will be “warm even for the period” like this weekend when Brussels is used to 20 ° temperature.
These conditions last for two or three weeks from September. Looking ahead, October and November are uncertain, but forecasts and trends indicate “The poorest month is November with a westerly ocean flow and consequently a lot of rain.“
“Total coffee junkie. Tv ninja. Unapologetic problem solver. Beer expert.”