On Saturday a rare tornado was seen on Lake Zurich. Photographs and videos were taken by those who saw it and posted on Twitter.
Tornados are rotating columns of air. They are caused when warm moist air meets cool dry air. When these two air masses meet, they create instability in the atmosphere – cold dry air ends up on top of much warmer moist air.
The recent tornado in Zurich is know as a waterspout because it occurred over a lake. Around 160 waterspouts are reported every year in Europe. Most of them occur in Spain, Italy and the Netherlands and most often in September. It is rare to see them in Switzerland.
Twitter link (in German)