They come and go unnoticed most of the time — mini-tornados that rise up from the ground and dissipate into clear, blue skies.
Dust devils. The name sounds menacing, but they're hardly formidable foes for humans.
They form almost anywhere in Utah — alleys, back yards, city streets.
Through polarized lenses on either sunglasses or cameras, the phenomenon comes in clearer and more defined, an amazing sight to anyone the least bit interested in strange, seemingly unexplainable weather anomalies.
Dust devils 101
Katharine Kanak is a research scientist for the Cooperative Institute for Mesoscale Meteorological Studies at the University of Oklahoma. Simply put, Kanak knows dust devils.
You can't predict the weather by studying the presence of dust devils, which often occur without a cloud in the sky. They're normally benign entities that form in the hot, dry conditions found in Arizona, Nevada, Utah and in places like Australia, home to plenty of dust and heat.
The National Weather Service logs reports from callers thinking they're seeing a tornado — a check of the radar and satellite images usually proves otherwise.
"Truth is, they're pretty common in the Intermountain West, especially in the summertime," forecaster David Hogan said. "They can look pretty impressive sometimes."
Kanak has seen them in Illinois and other unlikely places, though. Even in a subarctic climate, where the air temperature had reached 65 degrees Fahrenheit on one occasion, she has heard of a dust devil forming because there was enough air instability in the area.
When there is sufficient heating of the earth's surface and even the slightest gradient or change in temperature just above the surface, a dust devil can form. Cold air wants to sink while hot air naturally rises, combining to create a vertical motion.
How does the horizontal or spinning motion happen?
"It's a question that's still an issue of debate in this area of study," Kanak said. "How any atmospheric vortex starts spinning is an intriguing question."
Kanak differentiates between dust devils and urban "whirlwinds" caused by winds flowing around buildings. A true dust devil needs a key ingredient — dust.
Compared to their cousin, the tornado, dust devils rarely raise an eyebrow on the faces of weather watchers. Still, they have been known to pick up a car or two, overturn a mobile home, break windows and remove roofs.
Kanak's husband, a meteorologist, purposely ran through a dust devil. She recommends wearing goggles and earplugs.
"They whip around pretty well," Kanak said. "It's like being sandblasted, I heard."
Dust devils? Who cares?
Kanak cares.
She compiled her doctoral dissertation on dust devils, devoting the past five years of her life to their study.
There are still many unknowns.
"We hope some of the things we learn from studying dust devils might be applicable toward the study of tornadoes," she said.
One of the surprising things she and her colleagues have learned through computer modeling is that wind shears are not needed to form a dust devil. A computer simulation with no imposed winds, only surface heating, showed that vortices still readily formed.
"It was a little unexpected, maybe," she said.
Unlike tornadoes, dust devils are easier to study and gather data on due to their accessibility in the field.
Kanak and a handful of others are trying to understand the commonality of dust devils and how often they may occur while remaining invisible to the human eye. Radar evidence suggests they may persist without the presence of dust. Formations with multiple vortex structures pose even more questions.
"It's a small niche, because they're benign," Kanak said. Most meteorological research is in the area of storms and tornadoes. She plans to stick with dust devils.
"With nature and physics, we never really get there — we're always discovering something new that puts a question to what was before accepted as fact," she said. "That makes it fun to study. That's what makes it intriguing."
E-mail: sspeckman@desnews.com