Strange storm clouds observed Beijing residents

Strange storm clouds observed residents of Beijing on June 18. They resemble a mushroom cloud of a nuclear explosion. This cloud has covered Beijing, povisela over the city for about an hour, illuminating lightning illuminated the city evoking thoughts of any nuclear war and Armageddon.
According to the National Center for Atmospheric Research, they were ordinary cumulonimbus clouds that formed initially vertically, but when they began to meet with warmer layers of air, began to grow horizontally.