It's not a sight we're used to seeing here in Southeast Texas, but thanks to a very persistent ridge of high pressure keeping rainfall totals to historic lows, they may become more common.
A viewer sent this picture to our newsroom this afternoon, and I had never really thought this was something that we'd see here in the Brazos Valley.
Dust devils form when intense solar heating warms the air right along the surface of the Earth. The warmer air will rise, and if conditions are right, the air may start to rotate. If there is a plentiful supply of this hot air near the surface, the dust devil will continue to grow as the supply of hot air continues to rush into the vortex and feed it.
These dust devils or "Nevada Tornadoes" are usually seen in barren deserts, although they are apparently visible in Southeast Texas during the worst drought in history as well. In appearance, they resemble a desert tornado, but they are not attached to a cloud. In fact, they are usually seen on cloudless days because the Earth's surface has to absorb a lot of solar energy to heat the air near the ground to allow dust devils to form.
In addition to clear skies, dust devils also need flat terrain so that the very hot air near the surface will be nearly constant. In hillier areas, pockets of relatively warm and cool air tend to develop. Dust Devils thrive in environments where there is a large area of very hot air close to the surface. They're generally seen in the desert because there's lots of dust to be picked up which makes them visible to us. At the moment, there's plenty of that here thanks to rather persistent high pressure keeping things rather dry. Finally, they usually develop on a day when the wind is light and temperatures are relatively cool. This helps to facilitate that extreme difference in temperatures between the air just above the surface and the atmosphere.
Eventually this very hot air will run out and cooler air will move in and cut off the energy supply to the system and the dust devil will quickly dissipate. This entire cycle usually happens in a matter of seconds, so luckily Paula had a camera handy to capture this unusual sight!