Haboob

Source: Wikipedia

Haboob is an Arabic word to describe a type of intense dust storm carried on an atmospheric gravity current, also known as a weather front. Haboobs occur regularly in dry land area regions throughout the world. During thunderstorm formation, winds move in a direction opposite to the storm's travel, and they move from all directions into the thunderstorm. When the storm collapses and begins to release precipitation, wind directions reverse, gusting outward from the storm and generally gusting the strongest in the direction of the storm's travel.

When this downdraft of cold air, or downburst, reaches the ground, it blows dust up from the desert, creating a wall of airborne sediment that precedes the storm cloud. This wall of dust can be up to 62 miles wide and several feet in elevation. At their strongest, haboob winds often travel at 22 - 62 mph, and they may approach with little or no warning. Often rain does not appear at ground level as it evaporates in the hot, dry air - a phenomenon known as Virga.