What are the four different cloud groups and how are they classified?

1. High clouds-composed almost entirely of ice crystals, the bases of these clouds start at 16,500 feet (5,032 meters) and reach 45,000 feet (13,725 meters).

2. Cirrus - thin feather-like crystal clouds in patches or narrow bands. The large ice crystals that often trail downward in well-defined wisps are called mare's tails.

3. Cirrostratusis-a thin, white cloud layer that resembles a veil or sheet. This layer can be striated or fibrous. Because of the ice content, these clouds are associated with the halos that surround the sun or moon.

4. Cirrocumulus-thin clouds that appear as small white flakes or cotton patches and may contain super-cooled water.