The MODIS instrument onboard NASA's Terra satellite captured this true-color image of a large low pressure system off the coast of Iceland.
In the Northern Hemisphere, the circulation around low pressure systems is counterclockwise and inward, a result of the Coriolis Force. Air flowing inward in low pressure systems has no where to go but up. The rising air cools, and if it rises far enough, clouds and precipitation can form.
Image courtesy Jesse Allen, NASA's Earth Observatory based on data provided by the MODIS Rapid Response Team.