Cassini took 14 images of Saturn's north polar vortex on November 27, 2012 over a period of many hours as the planet rotated beneath it. The 14 images have been processed to remove the geometric effects of Cassini's oblique viewpoint and of Saturn's rotation, holding the outer bright ring of white clouds fixed. With these motions removed, you can see individual vortices rotating and shearing, and the central clouds rotating faster than the outer ones.
Here are two stages in the production of this animation, shown at low resolution to save bandwidth. Here are the original 14 images, animated:
And the 14 images, stretched and aligned on the white band of clouds: