One of those who filmed the trombone was Michael Davidsson - see the clip above.
On Tuesday, a drum pulled over Kalmar Sound between Öland and the mainland and many people caught it in the picture.
Then SVT's meteorologist Per Stenborg told SVT News Småland how the weather phenomenon occurs:
- They are always created from the underside of a heavy cloud, usually in heavy rain or thunderstorms. They usually show up in late summer when it is relatively warm and humid and when the seawater is heated.
- They can be really powerful right when they pass, but they are very narrow. Of course, if they are out at sea, boats should not be nearby. These are enormous forces, ”says Per Stenborg.