DOWNBURST - A small area of rapidly descending air beneath a thunderstorm. A downburst forms as a pocket of cold air in a thunderstorm that rushes down toward the ground. The strong winds in a downburst typically approach from one direction, so the winds are known as "straight-line winds." These strong winds can exceed wind speeds of 100mph or greater and cause significant damage equal to that of a tornado.
LIGHTNING - An electrical discharge within a cloud or between a cloud and the ground.
SEVERE THUNDERSTORM - A thunderstorm that produces hail at least 3/4-inch or greater, wind speeds of 58mph or greater, or tornadoes.