Extreme storms MeteoSwiss expert: "All the ingredients came together in the Maggia Valley"

The storms at the weekend hit the upper Maggia Valley hard. An expert explains how the extreme event came about - and what man-made climate change has to do with it.

Ticino was hit hard by the devastating storms at the weekend due to a special weather situation.

MeteoSwiss expert Marco Gaia explains to RSI what happened in the upper Onsernone Valley and especially in the upper Maggia Valley: "Once again, all the ingredients came together in the right quantity and composition within a few days to create a very intense line of thunderstorms," says Gaia.

These ingredients are: "Warm, humid air with winds at low altitudes, a disturbance at high altitudes that led to destabilization, and cold air that reached high altitudes."

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A month's worth of rain in just a few hours

Gaia explains further: "The line of thunderstorms that formed from these ingredients stabilized and developed continuously over the upper Maggia Valley. In just a few hours, as much rain fell as normally falls in a month."

MeteoSwiss had already issued a level 4 out of 5 advance warning for the whole of Ticino on Friday evening. Specific warnings were then issued a few hours before the extreme event, particularly for the upper Maggia Valley.

But Gaia admits that he had not expected such severity.

Extreme events are increasing due to climate change

"What happened exceeded our expectations. It was a possible scenario, but not the most likely one," says the expert.

Thunderstorm lines like the one that occurred in Mesolcina a week ago "are part of our climatology south of the Alps", Gaia continues, "but with the ongoing climate change, triggered by man-made warming, we also expect an increase in these extreme phenomena in Switzerland."