Dust storm off West Africa
A dust storm in western Africa, which began in late April, 2012, continued through early May, sending billowing clouds of tan dust over the Atlantic Ocean and the Cape Verde Islands. This very large plume of thick dust began blowing off the coast of Africa on April, 29 and extended from Mali to Cape Verde. Unusually dry conditions in Mali have been cited as worsening the potential for dust storms by drying marsh sediments, and as a potential cause for this event.
The Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard NASA's Terra's satellite captured this true-color image on May 2, 2012, four days after the dust storm began. In this image, the dust can be seen to be thinning and dispersing, compared to earlier images.
Most of the dust appears to be blowing across Mauritania (north) and Senegal (south). The coastal countries south of Senegal, The Gambia, Guinea-Bissau, and Guinea, are also covered by the curling band of dust. In the Atlantic Ocean, the Cape Verde Islands remain shrouded by a thick veil of tan dust. The north-east to south-west movement of the prevailing wind is written in both the dust and clouds near Cape Verde. Not only does the dust plume leave a trail in the sky, but cloud vortices can be seen on the leeward side of the islands.
Article is taken from: http://modis.gsfc.nasa.gov/