Harmattan

Image from newtopia

This dry easterly or northeasterly crosses the Sahara, picking up sand before it rages out over the Atlantic. The fine dust it carries travels hundreds of kilometres out to sea. It interferes with the machinery of aircraft and coats the decks of ships. This wind is strongest between November and March. In summer, cooler southwest winds can push beneath it and raise it aloft, causing tornadoes over western Africa.