Haboob!

The name haboob comes from the Arabic word "habb", meaning wind, and refers to a sudden dust storm triggered by the cold-air outflow from a decaying thunderstorm. Cold air from the mid-troposphere is dragged down by falling rain inside the thunderstorm. When the cold air hits the ground, it spreads out in all directions. If there is a dusty desert area below, the strong gusty winds of this cold air outflow will pick up the dust and mix it up to great heights. The edge of this cold air (called a "gust front") will then appear as a wall of dust up to 3000 feet high, moving across the desert at speeds of up to 50 mph. Haboobs are commonly seen in the Sahara desert, Iraq, Australia, and the Southwestern United States.