What is the name of the periodic storm on Saturn that appears roughly every 30 years?

The periodic storm on Saturn that appears roughly every 30 years is the Great White Spot. It is a vast atmospheric disturbance whose bright ammonia-rich clouds can become large enough to be seen from Earth through a telescope.

The phenomenon is not one permanent spot, but a series of recurring storms. Recorded examples include storms in 1876, 1933, 1960, 1990, and 2010–2011. The interval is not perfectly fixed: high-latitude storms may recur about every 27 years, while equatorial events are closer to 30 years.

The 2010 storm was tracked extensively by NASA’s Cassini spacecraft. It produced powerful convection, lightning, unusual chemical changes, and a planetary-scale disturbance that wrapped around Saturn. Scientists detected ammonia and water ice rising from deep in the atmosphere.

A common mix-up is with Jupiter’s Great Red Spot, which is a long-lived vortex rather than a periodic Saturnian storm. “Great White Oval” is also used as an alternate name, but Great White Spot is the standard answer to this question.