Clouds Associated With Tornadoes

Cumulonimbus Clouds

• Cumulonimbus clouds are tall clouds associated with several types of bad weather conditions, including hail, thunderstorms and tornadoes. They also produce lightning. They are easily noticed by their characteristic shape, which resembles that of an anvil. The flat top of the anvil often tapers off, pointing the direction in which the storm is moving. This type of cloud stretches above other cloud types and can further develop into a supercell.

Supercells

• The supercell is a thunderstorm with a rotating updraft called a mesocyclone. They are closely associated with hail, flash flooding and strong cloudbursts. The mesocyclone within the supercell can develop into a tornado, though only 30 percent do so. Supercells are found in both wet and arid climates, though the appearance of a supercell in an arid climate is usually less dangerous than those found in wet locales. This is because moisture helps keep them moving. Funnel clouds may form from a dry supercell, but it is rare that they turn into tornadoes.

Wall Clouds

• Wall clouds, also known as pedestal clouds, are cumulonimbus cloud formations which move horizontally across the earth. Rotating wall clouds, an occasional feature of such formations, are likely to produce tornadoes, particularly if the rotation is rapid. Most violent tornadoes are created out of wall clouds, and such tornadoes can last for minutes up to an hour. However, the formations usually begin as severe thunderstorms.

Funnel Clouds

• Funnel clouds form at the bases of cumulonimbus or cumulus clouds. They are swirling columns of wind and rain which may touch the ground or water below. A funnel cloud which touches the ground is technically a tornado or, if it makes contact over water, a waterspout. Though most funnel clouds do not touch the surface, they are still heard by those located below the cloud formation. The sound is often described as that of bees or a waterfall.