The greater the temperature gradient, the stronger the winds. Though Switzerland is not a classic wind country, winter storms and fall winds in the mountains (föhn) are significant factors.
In this country, Lothar is considered the storm of storms. The cyclone caused around 1.8 billion francs worth of damage and claimed the lives of 29 people. How could this have happened to us? Especially seeing as the inhabited regions of Switzerland are relatively well protected from heavy, large scale stormson account of their location and topography? The background here were extraordinary differences in pressure of up to 63 hectopascals over the Azores and a low pressure area above Iceland that led to equalizing winds across western Europe with cyclone strength.
In essence, in Switzerland the Jura Mountain chain and the Alps work like a windbreak for the Swiss midlands and the mountain valleys. Accordingly, severe storms in this country are rarer than in the coastal regions of northern and western Europe for example. However, thanks to their location certain valleys can turn into veritable wind tunnels. Alongside the midlands, these include the classic Foehn valleys in the Bernese Oberland, central and eastern Switzerland – when strong winds blow from Ticino or when the north wind triggers the north Foehn winds. Foehn cyclones are capable of buckling entire forests or pulling over building equipment and cranes – often leading to massive damage to buildings and infrastructure.
However, the highest wind speedsare, as a rule, measured at uninhabited places onmountain peaks, passes and ridges in the Alps and the Jura. As such the biggest Swiss wind energy parks are located on the Jura Mountains of northwestern Switzerland and on the Gütsch ob Andermatt.
When a wind blows at speeds of 75 km/h, it is classed as a storm (wind strength 9 on the BeaufortScale). Above wind speeds of 117 km/h, we are speaking of a cyclone (wind strength 12). As a rule, the most severe storms hit Switzerland around the winter as typical winter storms from a westerly direction. Hurricanes on the other hand do not occur here – they take place only in the tropics and the subtropics. The most severe winds in Switzerland – thankfully very rare and only occurring on a local scale are tornados. Somewhat more frequently,so-called waterspouts, a type of mini tornado, can be seen above lakes.
