ASK TOM: How do dust devils form?

Dear Tom,

How do dust devils form?

David Leonard, St. Isidore School, Bloomingdale

 

Dear David,

Dust devils are vigorous, short-lived (minutes long) whirlwinds that form on sunny days when warm air at the ground, strongly heated by the sun, is overlaid by much cooler, unheated air. The lighter warm air surges upward in a tight corkscrew spiral, clockwise or counterclockwise.

 

It’s almost like hot air spiraling upward in a chimney. At ground level, warm air sweeps inward and into the dust devil to replace air that is spiraling upward.

 

Dust devils are usually made visible by dust and other light debris like dry leaves. Dust devils are usually several yards across, typically grow to heights of a few hundred feet and contain winds of 20 to 40 mph.