Earlier this week, I was hiking up Candy Mountain with my wife. As we were headed up the slope, I noticed a lot of dust being lifted off a construction site on Kennedy Road. There had been occasional gusts, so at first I thought this was just a strong one, but a within a few seconds I was able to recognize rotation. We were watching a strong dust devil!
I didn’t catch on quick enough to get a video immediately, but we watched intently as the rotating column passed over a canal, and then over another construction site. This time, I was able to get a video:
This wasn’t the only large dust devil we saw, either. We also saw large dust devils in Pasco and another in the Badger Mountain South development that was there about ten minutes before the one I was able to take a video of. Dust devils are, of course, quite common in the Columbia Basin, so let’s talk about why that is and how they form.
There’s a common misconception that dust devils are mini-tornadoes. In reality, the only similarity between tornadoes and dust devils is that they are both vertically-oriented rotating columns of air. Dust devil formation is very different from tornado formation, hence why we have countless dust devils here but hardly any tornadoes.
Dust devils usually form on sunny days with very light winds and relatively cool temperatures on flat ground that has little cover. The sagebrush-covered undeveloped land around the Tri-Cities is perfect for this. When air temperatures on sunny days reach moderately warm temperatures such as the 70s and 80s, the ground can be significantly warmer. The ground then heats the air close to it, causing it to rise.
When this updraft is strong, it can initiate rotation which brings in more air and begin to move forward. If the surrounding ground is warm enough, the rotation will get stronger. In a sense, you can think of dust devils as a funnel, moving hot air from the ground vertically into the atmosphere.
Dust devils don’t have to have dust in them. They’ll only pick up dust if the ground is dusty (like the construction site the one above was passing over when I took the video). This dust devil didn’t dissipate between the construction site on Kennedy Road and the one in the video near I-182, it just didn’t have dust available to pick up.
Most dust devils are quite small – only a few feet in diameter with winds rarely exceeding 45 mph. That said, a limited number of them will become large and potentially hazardous. The one I saw in West Richland likely had winds around 50 mph, based on the size of the tumbleweeds I saw flying. I doubt that one caused damage.
Damage is possible in strong dust devils, though. In 2000, a dust devil in Arizona reached peak winds of 75 mph causing damage to many temporary structures at the fairgrounds in Flagstaff. There was even a small amount of damage to a permanent structure on the site.
Temporary shelters like canopies are obvious examples of structures that can be damaged and even hurt people when impacted by a dust devil. A frequent source of injuries and even intermittent deaths, though, is bouncy castles. I hadn’t really thought about this before reading up on injury-causing dust devils, but it makes complete sense. Just last month, a strong dust devil in China was able to lift a bouncy castle several dozen feet into the air, killing two and injuring 20 others.
That doesn’t mean you need to be afraid of bouncy castles. I may be in my mid-20s, but I still love them. Dust devils this strong are extremely rare, though it certainly does make a case for making sure you stake them (and any temporary structure) down well. Also, as always, it demonstrates a need for situational awareness. If you see a strong dust devil approaching a temporary structure, it’s okay to get people away from it.
I don’t want to end this post on a sad note, though. Dust devils are one of my favorite weather events and most of the ones in our region are well away from developed and construction areas. Once, in Kennewick, I was able to use a handheld anemometer out into a dust devil into my grandparents’ back yard. That one was smaller than the one I saw the other day in West Richland, but I measured wind speeds up to 35 mph.
If you see dust devils or other interesting weather, feel free to come over to my Facebook page – Tri-Cities Weather, or the group I set up specifically to discuss the weather of our region – Columbia Basin Weather Discussions!
