The phenomenon caught on camera shows a storm cloud essentially emptying: a microburst. What causes it?

In the US state of Arizona, a thunderstorm opened its floodgates. The video above shows how sudden heavy rain and hail falls from the cloud to the ground.

Downbursts often occur when there is a dry layer of air between humid air at higher altitudes. If a thunderstorm develops, some of the precipitation in this dry layer of air evaporates.

This creates a process of evaporative cooling, with the rate of evaporation increasing and the downdraft winds consequently strengthening.

The large core of rain and hail that the updraft had been holding in higher up in the cloud, then falls rapidly towards the ground. 

It drags a lot of cold air along with it, gaining speed as it travels downward, then deflecting and spreading outward rapidly once it hits the ground as squalls of strong winds.

They can often be confused with tornadoes, as the gusts can be just as strong and devastating, even up to 100 mph in severe cases! They are more common than tornadoes however, and form in different ways.

When the damaging winds of a downburst are confined to an area less than two and a half miles across its known as a microburst, otherwise it's a macroburst.