NASA’s Suomi NPP satellite captured semicircular outflow boundary over Mali.

Credit: NASA

The arc shape cloud hovering Mali is the product of an outflow boundary associated with a decaying thunderstorm. The falling rain from cumulonimbus thunderstorm clouds cools the air and creates a downdraft that spreads outward in a circular fashion once it reaches the ground. The outflow boundary, or a gust front, is the leading edge of a spreading pool of cool air near a thunderstorm, which can persist for many hours.

The local scenery on the ground is as follows.

Credit: Wikipedia

Reference: An Outflow Boundary—Not a Jellyfish—Over Africa (NASA Earth Observatory)
See earthview photo gallery: LiVEARTH