A cosmic storm is a type of phenomena generated by supernovae.
A storm began as an energy or power field which erupted into a large electromagnetic or gravitational disturbance in space. Storms were of varying sizes and intensities, with effects ranging from minimal to catastrophic. The crew of the USS Enterprise encountered a few of them in the 23rd century.
In the year 2266, a field appeared without warning near the Enterprise and quickly grew into a cosmic storm. Spock said there were no records of a starship surviving a cosmic storm. This phenomena was a gravitational vortex which drew the starship into a pocket universe. Following its escape, the ship headed to Starbase 9 for minor repairs. (TOS comic: "Museum at the End of Time")
Later in 2266, the Enterprise encountered a cosmic storm. Its approach was signified by interference to the Enterprise's navigational laser beam. The effect on the Enterprise by the storm was minimal; the ship was physically shaken, but suffered no damage. (TOS comic: "UK comic strips, first story arc")Also in 2266, the Enterprise encountered a gigantic cosmic storm close to the Solar system which they could not outrun or evade. It pummeled the ship with waves of massed energy that significantly reduced shield effectiveness, allowing radio waves and other forms of energy to penetrate through to the bridge. The storm caused a major crack in the forward secondary hull. Spock welded the outer fissure, but damage was extensive enough to require a slow trip to the lunar repair base. At the Engineer's Club bar on Earth, Montgomery Scott lamented having lived through three cosmic storms, which his drinking partner thought was more than anyone. (TOS comic: "Furlough to Fury")
A cosmic storm appeared unexpectedly in front of Enterprise shuttlecraft Galileo during a trip to Quodar in 2266. Its pilot, Pavel Chekov, was unable to avoid the storm, which disrupted the shuttle's guidance system. The ship landed safely on nearby planet Tristas. (TOS comic: "The Final Truth")