Remember when I posted those cool videos from lab experiments that replicated Saturn's hexagon? It turns out that Saturn's not the only place that displays geometrical shapes in its atmosphere. Earth does too. The kinds of wind velocity gradients that may have created Saturn's hexagon exist here as well. Here's a satellite photo of Hurricane Isabel with a pentagon (or maybe a pentacle!) for an eye.
Hurricane Isabel's pentagonal eye
Hurricane Isabel slammed into the American eastern seaboard in mid-September 2003. This satellite view shows its eyewall containing five vortices, setting up a pentagonal shape.