Definition of "mesocyclone" [mesocyclone]

• An area of vertical atmospheric rotation in supercell thunderstorms, which signals the threat of a possible tornado. (noun)

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• "The horizontally rotating mass, called a mesocyclone, is the first clue to radar observers that a thunderstorm could produce a tornado."
• "With enough air shooting up and down, the pinwheel is knocked on its side, creating a huge rotating mass of clouds called a mesocyclone - the hallmark of a tornado-spawning supercell storm - from which a funnel cloud can shoot down."
• "The rotating updraft of a supercell (called a mesocyclone when visible on radar helps the supercell to produce extreme severe weather events, such as giant hail (more than 2 inches in diameter, strong downbursts of 80 miles an hour or more, and strong to violent tornadoes."