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July 6, 2011 / Dave Gorham

“Attack of The Dust Cloud!” (Actually A Pretty Normal Occurrence)

“Been there, done that,” as the saying goes. Not to diminish yesterday’s dust storm in Phoenix, but seeing the images of the massive brown cloud rolling across the city reminded me of a similar storm some 25 years ago in southwestern Oklahoma. At the time, Altus, Oklahoma was home and I remember gunning my truck south on Highway 6 trying to outrun the looming brown cloud that was threatening to turn day into night while my wife, Tonie, fumbled for the camera.  We eventually reached the “safety” of the city and were home just a few moments later. Sure enough, the dust enveloped us as we nervously watched through the windows of our home. I’m a New Yorker and Tonie’s from Florida — this was our first dust storm and we were waiting for the house to rumble or shake like an earthquake.

This AP photo shows yesterday's dust storm as it moves over Phoenix.

I don’t know why I thought there would be something more to the dust storm than just dust and wind. Maybe it’s because it looks so — well, biblical. Like some supernatural force has descended upon the Earth to wreak havoc and destruction. When it was all over and the sun began to shine through a few minutes later I remember thinking, “That’s it?”

Dust storms are not inconsequential. Sudden visibility restrictions across airports or interstates can cause accidents and death. Dust sneaks into places like your car, under your window sills, into your pool, into your food.

This NOAA image demonstrates a downburst of wind as it interacts with dust. Image: NOAA

Of course, dust is only one ingredient to a dust storm. Gusty winds will always accompany the dust. My brother, a former Phoenix resident, would quickly gather up pool and patio furniture when he would see the dust cloud coming, as “sometimes things would just vanish.” The joke back in Altus used to be that the topsoil was just passing through.

But the conditions that triggered yesterday’s dust storm are not uncommon and occur almost daily across the United States. Phoenix is in the midst of their thunderstorm, or monsoon, season. This allows strong thunderstorms to develop over normally dry and dusty regions of the Southwest, and since gusty winds are part of the natural life cycle of a thunderstorm, dust storms can then become part of the thunderstorm equation. The stronger the thunderstorm, the stronger the wind (downburst) potential. And if an area hasn’t seen rain in some time, the accumulated dust is just waiting for a ride to the next ZIP code. Typically dust storms will occur late in the afternoon or early in the evening as the strongest thunderstorm winds occur as a thunderstorm — which forms in the heat of the day — enters its dissipating stage. Any thunderstorm has downburst potential and any location can experience the strong gusty winds, often called a gust front or outflow boundary. It’s just that in places like Phoenix and Altus, dust caught up in the wind makes the whole thing so easy to see.

A thunderstorm's life cycle includes the dissipation stage. At this time, when the thunderstorm begins to fall apart, strong winds rush downward to the surface. As the winds spread out below the storm, the strong gusty winds can travel for miles and miles. Image: Wikipedia

As it happens, thunderstorms are once again in the forecast for southern Arizona today and dust storms should be considered.

Once again, thunderstorms are in the forecast for parts of Arizona and the Southwest. Downburst winds may once again kick up the dust and create dust storms like yesterday. Image: ImpactWeather Gmaps














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