Astronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2014 May 21



A Supercell Storm Cloud Forming over Wyoming

Video Credit: Basehunters (BasehuntersChasing) Music: Empire (Shakira)

Explanation: How do supercell storm clouds form? Pictured above is a time-lapse video taken last Sunday detailing the formation of one such violent supercell in eastern Wyoming, USA. Starting as part of a large and dark thunderstorm complex, the supercell comes together along with a large rotating updraft of air known as a mesocyclone. Mesocyclones form during rapid changes in wind speed and direction with height and can produce torrential rain, damaging hail, swirling winds, and sometimes tornadoes. Storm watchers are seen studying, imaging, and ultimately running from the developing storm cloud during the video. During the middle part of the video, the kilometer-wide supercell can be seen swirling ominously with a nearly flat bottom. Toward the end of the video, another swirling supercell cloud forms but then quickly dissipates.