What are 'dust devils' and are they dangerous?
TUCSON, Ariz. (KGUN)  A common sight drifting across the Sonoran Desert is a dust devil. Some are small and last only a few seconds while others last for several minutes while reaching high into the sky above. KGUN Most dust devils last only a few minutes but some have been observed to last almost 20 minutes as they make their way across the desert. Dust devils get their name from the dust they pick up and spin into the air. Dust devils can form any time of the year but are most common during the warmer months and come to life on relatively calm, sunny days when the sun heats the ground and the warm air rises. As the warm air quickly rises through cooler air above, a shallow layer of instability which creates a small area of low pressure. A vortex of low pressure develops which draws even more warm air into the swiftly rotating column of air. The column of air grows bigger and continues to rise. Eventually, the rising air encounters cooler air and draws more cool air into the vortex. When this happens, the dust devil starts to dissipate and collapse. KGUN Many times, the damage from a dust devil is confused with that of a microburst. However, in order to have microburst wind damage, there must be thunderstorms in the area. According to the National Weather Service, dust devils can grow to be quite large and can cause quite a bit of damage. Most dust devils grow to be less than 100 tall but some can grow to over 3,000 feet! Most will generate wind speeds less than 45 mph, but the biggest dust devils can pack winds up to 80 mph which can cause significant damage to small structures and trees. Many times, the damage from a dust devil is confused with that of a microburst. However, in order to have microburst wind damage, there must be thunderstorms in the area. Microbursts are caused by strong downdrafts generated by thunderstorms. On a sunny day, damage was likely the result of a dust devil or random gust of wind. Even though injuries are uncommon, dust devils do occasionally cause injuries because of blowing debris. A strong dust devil ripped through the Coconino County Fairgrounds in Flagstaff on September 14, 2000 and caused severe damage to several stands and booths. Some injuries were reported but, fortunately, no fatalities. The Flagstaff National Weather Service looked at the damage associated with the dust devil and estimated wind speeds had to be around 75 mph which would compare to a weak tornado! You might be surprised to learn that there have been fatalities as a result of dust devils. In May of 2003, a strong dust devil tore the roof off a two-story garage in Lebanon, Maine. The building collapsed and killed a man inside. Dust devils have also been known to contribute to accidents involving small aircraft, paragliders and parachutists. Most dust devils last only a few minutes but some have been observed to last almost 20 minutes as they make their way across the desert. They can form in higher terrain, but this isnt likely as dust devils much prefer flat surfaces where the vortex can easily form and not be disturbed by surrounding variations in landscape. If you want to attempt to photograph dust devils, go west of Tucson to Avra Valley where they are a common sight. Just remember to choose a sunny day because well rarely see a dust devil form on a cloudy day because of the need for sunshine to warm the ground. Also, the air must be pretty dry to allow the column of warm air to rise rapidly. On a humid day, its much more difficult for air to rise. Dust devil is the name we commonly hear and use to describe these desert weather phenomena but there are several other names depending on where you live. Dirt devil, dancing devil, sand auger and the Navajo term of chiindii are just a few of the names you may hear around the United States. However, around the world, you may hear other terms. One name that will likely generate a chuckle is a name that comes to us from our friends down under in Australia. In the land of the kangaroo, a dust devil is known as a willy-willy! KGUN Dust devils can grow to be quite large and can cause quite a bit of damage. Most dust devils grow to be less than 100 tall but some can grow to over 3,000 feet! No matter what you call them, dust devils are as much a part of the desert as saguaros, roadrunners and coyotes. Even though most pass harmlessly across the desert floor, its still a good idea to stay out of their way when possible!