The following images illustrate some of the complex patterns that develop in Earth's atmosphere.

Left: GOES-7 image of weather patterns in the Americas and Eastern Pacific.
Middle: Hurricane Fran from GOES-8 (Ref).
Right: GOES-8 false-color image of water vapor in Earth's atmosphere

How does this complex behavior arise? The most general answer is that it is a consequence of (1) solar heating, and (2) effects associated with the rotation of the Earth.