Lightning that occurs within a cloud is known as lightning. Another name for a/an thunderstorm is a "pulse" thunderstorm. Tropical and regions receive the most thunderstorms each year. The three elements that are necessary for a thunderstorm to form are moisture, , and instability. An air mass that's warmer than the surrounding air and continues to rise is considered . During a thunderstorm, a downdraft forms during the stage. is a shockwave in the form of a sound wave that results from the rapid expansion of air following a flash of lightning. During the stage of a thunderstorm, the downdraft begins to weaken or eliminate the updraft.