Our amazing planet.

Gallery: Reading the Clouds



(Image credit: NOAA)

As they develop vertically upward they may go from small, fair weather clouds to large, boiling monsters called cumulonimbus, also called thunderheads.

Such clouds are most often associated with cold fronts: When a mass of cool, dry air pushes into a warm, moist air mass, the heavier cool air acts like an atmospheric plow and pushes the warm air up into violent thunderstorms. High winds aloft can make the cloud's top into a flat anvil-like shape and their bottoms are usually very dark.

These clouds can forecast some of the most severe weather including torrential downpours, vivid lightning, hail and even tornadoes.

Mammatus Clouds


(Image credit: NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL))

Clouds that look like hanging bulges from the skies are called mammatus clouds. More often than not, references statr that such clouds are a forbearer of severe weather, but actually, just the opposite is true: These clouds are formed by sinking air and are sometimes seen after a potent thunderstorm; they signal that a storm is retreating, not approaching.

Joe Rao is a television meteorologist in the Hudson Valley, appearing weeknights on News 12 Westchester. He has also been an assiduous amateur astronomer for over 45 years, with a particular interest in comets, meteor showers and eclipses. He has co-led two eclipse expeditions and has served as on-board meteorologist for three eclipse cruises. He is also a contributing editor for Sky & Telescope and writes a monthly astronomy column for Natural History magazine as well as supplying astronomical data to the Farmers' Almanac. Since 1986 he has served as an Associate and Guest Lecturer at New York's Hayden Planetarium. In 2009, the Northeast Region of the Astronomical League bestowed upon him the prestigious Walter Scott Houston Award for more than four decades of promoting astronomy to the general public.