What is a haboob?

A haboob forms when cold air rushing down out of a thunderstorm hits the ground and spreads outward, scooping up loose dust and sand. The result is a moving wall of dust that can rise 1,500 metres or more and stretch for tens of kilometres. The name comes from the Arabic word 'habb', meaning to blow, and the storms are common in Sudan, the Sahara and the Arabian Peninsula. They also strike the southwestern United States, especially around Phoenix, Arizona, during the summer monsoon. Visibility can drop to almost zero within minutes, making haboobs dangerous for drivers and aircraft.