In the wake of the weakened cold front, a powerful thunderstorm cell passed through Zurich yesterday, Monday evening, August 13, 2018, painting impressive clouds over the city in the evening mood.
The cold front that arrived in the afternoon brought only a little rain. However, a very powerful thunderstorm cell subsequently reached the canton. This cell came from the west and reached Zurich at around 7:20 p.m. and reached its greatest potency. In addition to some precipitation, ominous-looking clouds were the signalers and aftermath of this supercell.
Gust Roller
Of particular interest was a gust roller, also known as a shelf cloud (sh). Such clouds form in front of and to the side of a pronounced Cb on a horizontal axis (hence roller) and are reminiscent of a shell (hence shelf). Sometimes they are slightly curved (dome-shaped), frayed and very dark, which can appear impressive or even threatening. Gust rollers are then actually very turbulent. To put it very simply, they form in the shear zone of strong updrafts (suction of overdevelopment) and strong downdrafts (cold air discharge due to rainout). They rotate around a horizontal axis and form a shelf cloud. As already mentioned, this explanation does not do justice to the complexity of the phenomenon. Perhaps the following images will.
In addition to our own pictures, there are pictures of Roundshot-Kameras.
