Monday, August 15, 2011

Haboobs - Desert Dust Storms

August 15, 2011 © Thomas J. Kollenborn. All Rights Reserved.

Summer storms in the desert are often known as the Monsoons. These storms bring massive thunderstorms with dust, heavy showers, lightning, dust storms and sometimes devastating wind called a “micro burst.”

During the summer months most of the storms over central Arizona and the Superstition Wilderness Area result from warm moist air flowing in from the Gulf of Mexico and the Sea of Cortez (Gulf of California). This warm moist air moves across Texas, New Mexico and Mexico. Mountains force this warm moist air upward forming clouds filled with moisture sometimes saturated to the maximum.

These clouds release their moisture as they rise and cool. This is known as orographic lift. The massive anvil-shaped thunderheads clouds that form over Superstition Mountain from July to September are normally formed by two methods, orographic lift and convectional activity. The convectional storm clouds result from rapidly rising and expanding warm moist air and falling cold moist air. This uneven heating of the Earth’s surface is caused by the open cloud pattern in the atmosphere.

Lightning can be caused by the attraction of unlike electrical charges within a thunderhead cell. The rapid movement of ice and water molecules going up and down in a thunderhead cell creates friction that results in an enormous amount of energy being produced in the form of static electricity. A single lightning discharge can produce about 30 million volts at 125,000 amperes. This discharge can occur in less than 1/10 of a second. The results of a lightning strike can be horrific. Never make yourself a target for a lightning strike by being caught in an high, open area or by standing near a natural lightning rod such as a lone tree on a ridge.

The rapid rising and falling of warm and cold moist air also can create violent bursts of energy. This type of activity results in micro burst both small and large. Small micro bursts can develop winds momentarily up to 200 mph. The also can create winds across wide area up 80 mph. These are the winds prior to precipitation can create huge dust storms. These dust storms can momentarily be 100 miles wide, over a mile high and capable moving tons of desert fines (dust). These storms in northern Africa and the Middle East are known  as Haboobs as they roar out of the Sahara desert. Since the late 1960s this Middle East name has been  attached to Arizona dust storm. Some of these dust storms are enormous and extremely dangerous for the transportation.

What is the cause of these dangerous dust storms? The most recent dust storm on Tuesday, July 7, 2011 was certainly one of the largest ever experienced by this state. These dust storms appear to be far more severe in recent years. A lot of the Sonoran Desert in Central Arizona has been disturbed for housing pad development on thousands of acres and then the housing boom died. Now this land set barren and undeveloped. What little vegetation that covered the desert before preparation for development has been removed. Also unpaved roads and the irresponsible use of ATV and other vehicles off road contribute to the problem. All of this certainly a part of this problem of dust storms blowing toward the Salt River Valley from Central Arizona. Yes, there are many other factors to include into this equation including agriculture, arid condition, and uncontrolled growth.

The monsoons are associated  with very dangerous factors we should all be aware of. These factors include dust storms, high winds, lightning, and flash floods. I have mentioned the other factors in previous columns. If you are caught in a dust storm use common sense to survive. Get as far as you can off the highway right-of-way, park your vehicles and turn off your lights. Don’t keep your foot on the brake pedal. There are still those who drive in dust and fog at very unreasonable rates of speed endangering themselves and other. If they see your brake lights they might drive right off the highway and into you vehicle.

 Our desert is being disturbed more and more each year and the dust storms will probably become more prominent, dangerous and severe. If we are not careful we will be looking like Oklahoma during the “Dust Bowl” of the 1930s. Oklahoma’s “Dust Bowl” was caused by drought primarily during the 1930s. There has been an effort by the cities, state, and counties to suppress the problem with some dust control methods such as paving dirt roads and trying to limit the number ofacres of land for vegetation removal for  development.

These methods only help, however during periods of drought dust storms are part of living in the Southwest deserts.