[h=2]Dust Devils
Dust devils are a common wind phenomenon that occur throughout much of the world. These dust-filled vortices are created by strong surface heating and are generally smaller and less intense than tornados. Their diameters typically range from 10 to 300 feet (3 to 90 m), with an average height of approximately 500 to 1,000 feet (150 to 300 m). Dust devils typically last only a few minutes before dissipating. However, when conditions are optimal, they can persist for an hour or more. Wind speeds in larger dust devils can reach 60 mph or greater.
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Dust devils form in areas of strong surface heating. This typically occurs under clear skies and light winds when the sun can warm the air near the ground to temperatures well above those just above the surface layer.
Once the ground heats up enough, a localized pocket of air will quickly rise through the cooler air above it. Hot air rushes in to replace the rising air at the bottom of the developing vortex, intensifying the spinning effect. Once formed, the dust devil is a funnel-like chimney through which hot air moves both upwardly and circularly. If a steady supply of warm, unstable air is available, the dust devil will continue to move across the ground. However, once that supply is depleted or the balance is broken in some other way, the dust devil will break down and dissipate.
Dust devils can vary greatly in size, both in diameter and vertical extent. Notice how aggressive the interaction with the surface can be.