3. Asperatus

An "asperatus" cloud rolls over New Zealand's South Island in an undated picture. This apparently new class of clouds is still a mystery. Photograph courtesy Merrick DaviesExperts suspect asperatus clouds' choppy undersides may be due to strong winds

2. Cumulonimbus Supercell

Big Sky CUMULONIMBUS Cloud - II A little later, as the sun set, the storm looks quite different. This kind of complete view of a thunderstorm cloud is typical of the US Great Plains - Big Sky country. Photo by Kay Cunninghan, a Texas rancher, May

6. Anti-twilight arch

Arch anticrepuscular, the shadow of the Earth's atmosphere.

Nebraska Supercell

The Lovely Monster Over the Farm Lodgepole NE, 22 June Seaman Big Cloud series

7. Aurora Borealis - October 9th 2012 - Canada

7. Aurora Borealis - October 9th 2012 - Canada

5. Hurricane Katrina

Cyclone Catarina, a rare South Atlantic tropical cyclone viewed from the International Space Station on March 2004

4. Mammatocumulus

Mammatus, also known as mammatocumulus (meaning “mammary cloud” or “breast cloud”), is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud. Photograph by Matt Saal.