The bright cirrus-like clouds of Neptune change rapidly, often forming and dissipating over periods of several to tens of hours as seen in this sequence spanning two rotations of Neptune about 36 hours by NASA Voyager 2.

Neptune – Changes in Great Dark Spot

The bright cirrus-like clouds of Neptune change rapidly, often forming and dissipating over periods of several to tens of hours as seen in this sequence spanning two rotations of Neptune about 36 hours by NASA Voyager 2. http://photojournal.jpl.nasa.gov/catalog/PIA00047