A man has died after his car was swept away during a flash flood caused by a thunderstorm in Des Moines, Iowa, on Saturday 30 June 2018. Radio sports commentator Larry Cotlar, 66, was one of three drivers whose vehicles were swept off roads by floodwaters during the storm, and was later found dead; the other two drivers were rescued safely. The incident happened as a series of thunder storms formed across Polk and Dallas counties, with over 250 mm of rain falling in under three hours in some places, resulting in a series of flash floods across the area, with one waters exceeding five metres in places, resulting in the flooding of many roads and buildings.
Thunderstorms are caused by heating of the land or water surface by the sun, causing air to expand, and thus rise, this causes more air to be drawn in to fill the gap, which is in turn heated and rises, repeating the process and creating a cycle. As the air rises it expands, and therefore cools, losing its capacity to retain water, leading to precipitation (rainfall), with higher levels of rainfall occurring when the initial air mass is warmer and more humid.
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