These incredible shots were captured by Marko Korosec, 31, a storm chaser on a recent month-long trip to the USA.
The pictures, which were taken in "Tornado Alley" as Korosec travelled through Texas, Kansas and Colorado, were shot from a distance of 1km as the giant supercells ripped up the landscape.
They shapes form when warm and cold air mix, creating a rotating column, which gives the clouds the unusual circular shape.