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Lighting and supercell storm. Lightning strike within a tornado warned supercell thunderstorm. A supercell thunderstorm is a severe long-lived storm within which the wind speed and direction changes with height. This produces a strong rotating updraft of warm air, known as a mesocyclone, and a separate downdraft of cold air. Tornadoes may form in the mesocyclone, in which case the storm is classified as a tornadic supercell thunderstorm. The storms also produce torrential rain and hail. Photographed near Burlington, Colorado, USA. (KEYSTONE/SCIENCE PHOTO LIBRARY/ROGER HILL/SCIENCE PHOTO LIBRARY)