It’s the question on the minds of quite a few people, some of whom grew up using the phrase “dust storm” to encompass all masses of wind-blown dirt. So why isn’t what happened in West Texas on Wednesday just a “dust storm”?
We all know that warm air rises and cold air sinks. Our warm rising air is responsible for thunderstorm updrafts, those towering puffy clouds you often see in spring and even summer. In contrast, cold sinking air is responsible for downdrafts, which we often see in the form of rain. But air can’t rise and sink forever. Imagine a balloon. When our warm balloon reaches the stratosphere, the surrounding temperature begins to warm with height, and the air inside our balloon is no longer warmer than the air around it. The balloon stops rising as if hitting a ceiling. This is how thunderstorm anvils form, and they spread out and away from the updraft as more and more of our balloons hit the ceiling.
Now picture that balloon again, but with water instead of air inside of it. This is our downdraft. Gravity brings this balloon down to the surface, too cold and too heavy to stay aloft. Have you ever watched a water balloon hit the ground? When it hits the floor, it bursts and the water spreads out just like our air-filled balloons do when they hit the “ceiling”. This cold air spreading out away from our thunderstorm is called “outflow”. We frequently see outflow in the form of a shelf cloud, those wild formations that stretch across the horizon.
When a strong downdraft hits the ground in the desert, the dust at the surface is kicked up into the air. As the outflow continues to spread out, it picks up more and more dust behind it. The winds in these thunderstorm-fueled dust storms can reach upwards of 50 MPH, and the stronger the winds, the more dust it picks up. Visibility can plummet to zero in a matter of seconds. It’s a dust storm on steroids.
In 1971, scientists witnessed one of these incredible dust storms in Arizona during the summer monsoon. They published an article, “An American Haboob”, in the October 1972 issue of the Bulletin of the American Meteorological Society, comparing the intense American dust storms to the infamous Sudanese haboobs. They argued that while the American counterpart was less frequent, it shared the same mechanics and intensity and thus should share the same name. So sure, I guess we kind of borrowed the word nearly 50 years ago, but there are quite a few of them we’ve also borrowed over the years (like “tsunami”).
Just as we call a rotating thunderstorm on steroids a “supercell”, we call a dust storm on steroids a “haboob”. It has nothing to do with “embracing foreign words” and everything to do with the science of giving a specific phenomenon its own name. Remember this as we enter the summer monsoon, prime time for collapsing thunderstorms in the Desert Southwest; they may not be in Texas, but we’ll be seeing more photos of haboobs in the months to come!