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What is a dust devil?



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What is a Dust Devil?

Mojave Desert-Between Barstow & Baker
Dust devils are a common wind phenomenon that occurs over the deserts of southern California.

These dust-filled cyclones form by strong heating of the surface, and normally are much smaller and intense than a tornado.

The typical diameter of a dust devil ranges from 10 to 300 feet, with an average height of approximately 500 to 1,000 feet...normally only last a few minutes.

Dust devils form in areas of strong surface heating and usually occur under sunny skies and light winds, when the ground can warm the air to temperatures well above the temperatures just above the ground.

Once the ground heats up enough, a localized pocket of air will quickly rise through the cooler above it. The sudden uprush of hot air causes air to speed horizontally inward to the bottom of the newly-forming vortex. This rapidly rising pocket of air may begin to rotate, and if it continues to be stretched in the vertical direction, will increase in rotation speed. This increase in rotation speed from vertical stretching is similar to the increased spinning of an ice skater as they bring their arms in toward their bodies. As more hot air rushes in toward the developing vortex to replace the air that is rising, this spinning effect is intensified. As the air rises, it cools and eventually will descend back through the center of the vortex. Under optimal conditions, a balance between the hot air rising along the outer wall of the vortex and the cooler air sinking in the vortex occurs. The dust devil then begins to move across the ground, picking up more and more dust, which highlights the vortex making it visible to the eye. The dust devil, once formed, is a funnel-like chimney through which hot air moves both upward and circularly. If a steady supply of warm unstable air is available for the dust devil, it will continue to move across the ground. However, once the warm unstable air is depleted or the balance is broken in some other way, the dust devil will break down and dissipate.

...Here in southern California...
Dust devels are often visibible while driving along the 10 FWY from Palm Springs east to the Colorado River,
along the 15 FWY from Hesperia northeast to the Nevada state line,
along the 14 Freeway through the Antelope Valley and...
along the 58 from Mojave east to Barstow.

Along the 15 Freeway near Barstow

Some of the information above, courtesy of the...
National Weather Service website in Flagstaff, Arizona.

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