The movement of the huge cloud was displayed in a fast-moving manner, and was monitored in the city of Caxias do Sul in Brazil.This cloud is known in meteorology as the "shelf cloud", which is a large-scale cloud formation in the form of a wave that usually precedes storms, and is formed when an area with high temperature meets cold air, according to the Brazilian channel "G1". "Clouds usually form when the temperature is high on the ground and encounters a layer of cold air, and it is also preferred by strong winds that operate in the first layers of the atmosphere," she said."These clouds 'shelf' form when there is a great deal of instability, as warm air rises above a layer of cold air, and the cloud condenses quickly, creating an effect that is as beautiful as it is scary."