Downburst

When the wet air in a thunderstorm meets the drier air surrounding it, the water in the air evaporates. When water evaporates, it cools the air around it. Since the cool air is denser, it rapidly sinks to the ground and creates strong winds called downbursts. The downburst can actually suck more dry air into the storm, making even stronger downbursts or clusters of downbursts. Derechos happen when the right conditions for downbursts occur over a wide area.