The storm the second one to hit the area in the last two weeks formed south of Phoenix in Pinal County before heading northeast to the city. The National Weather Service said the dust wall was about 3,000 feet high and created winds of 25-30 mph, with gusts of up to 40 mph. The previous dust storm on July 5 was one of the largest storms to hit the area. It shrouded Phoenix in grey and brown dust, shut down the Phoenix Sky Harbor International Airport grounding all planes and caused major power outages throughout the area.
Health officials recommend eye and respiratory system protection for anyone who must be outside during a storm. The dust can bring about an increase in a disease known as Valley Fever, a fungal pneumonia. Valley Fever thrives in the hot and arid Southwest in dirt found just a few feet beneath the earth’s surface; it can be stirred up by construction, wind and other activity.
These types of storms are called haboobs. They are intense sandstorms commonly observed in arid regions throughout the world, including the desert regions. They are frequently observed in the deserts of Arizona, including Yuma and Phoenix, as well as New Mexico and Texas. They have been observed in the Sahara desert (typically Sudan), as well as across the Arabian Peninsula, throughout Kuwait, and in the most arid regions of Iraq. The wall of sand can be up to 60 miles(100 km), wide and over a one mile high in elevation. At their strongest, haboob winds can travel at 20-30 mph (35-50 km/h), and they may approach with little to no warning. (wiki)