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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Whirlwinds kick up dust and pique fascination

I was sitting in my living room last Tuesday afternoon, looking out the window. Skies were sunny, winds were relatively light and temperatures were in the upper 80s.

All of a sudden, I heard the rush of a roaring wind. Next thing I knew, my trees were bent over sideways and small objects were sailing across my backyard. I ran to my weather station and noted winds between 35 to 40 mph. A whirlwind had just passed over my house. I have to admit I was pretty excited about the whole incident.

Growing up in the Midwest, I lived through more tornado warnings than I could count. As a college student studying meteorology I would jump in my car and go after such storms, but unlike chasers I would not get so close that I could literally feel the destructive winds breathing down my back. That is what brings me to my great fascination with whirlwinds – or the ones that pick up a lot of dust, “dust devils.” You can really get up close and personal to these things.

It wasn’t until i was in my early 20s in Oklahoma that I saw my first dust devil. It was small and short-lived, but it passed right in front of my car. In August 1999, I found myself relocating to the Inland Northwest with my husband. We were driving through Central Washington and there were dust devils large and small forming and dissipating all around us in the open fields. Many would cross the road in front of us, the tumbleweeds flying. I felt like a kid in a candy store to be so close to these “mini tornadoes.”

Technically speaking, however, these whirlwinds or dust devils are not really mini tornadoes. Though they may resemble each other in form, each occurs under completely different circumstances and in very different environments. Tornadoes are usually (but not always) a product of an intense thunderstorm called a supercell. These types of storms form in an environment of warm and humid air. Wind speeds from tornadoes can range anywhere from 40 mph to more than 200 mph.

Dust devils on the other hand, tend to form in a hot and dry environment under clear skies with very light winds. There is no parent storm or even a cloud to spawn them. They are born at “hot spots” in a dry field, over pavement or really over any surface where the air in a particular spot can be heated a little more than the surrounding air. This heated parcel of air begins to rise, and as a result a small area of low pressure is created near the ground at that point.

Air near the surface rushes in toward the area of low pressure and can “spin up” or begin to rotate (either clockwise or counterclockwise). If this happens in a dusty field, dirt and debris can be carried up into the spinning air giving it that tornadolike appearance. In the relatively dust-free area of my neighborhood, the recent whirlwind was practically invisible save a few stray plastic grocery bags and loose leaves seen high in the sky. Though most dust devils have relatively weak winds and cause no damage, some larger ones can have winds in excess of 60 mph. On average, dust devils range in size from 10 to 300 feet in diameter and rise to an average height of 500 to 1,000 feet.

Michelle Boss can be reached at weatherboss@comcast.net