Funnel cloud

A funnel cloud approaching the ground in Douglas, Oklahoma on May 24, 2008

A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud (usually a cumulonimbus or towering cumulus cloud) but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud base. Funnel clouds form most frequently in association with supercell thunderstorms.

If a funnel cloud touches the ground it becomes a tornado. Most tornadoes begin as funnel clouds, but many funnel clouds do not make ground contact and so do not become tornadoes. Also, a tornado does not necessarily need to have an associated condensation funnel—if strong cyclonic winds are occurring at the surface (and connected to a cloud base, regardless of condensation), then the feature is a tornado. Some tornadoes may appear only as a debris swirl, with no obvious funnel cloud extending below the rotating cloud base. A funnel cloud is quite noticeable as it passes overhead aloft. The sounds heard are described as buzzing bees, roaring, a sucking sound, or a waterfall-like sound. A pressure drop is often noticeable as well, in the form of popping ears in anyone below the funnel cloud. A funnel cloud that touches down on, or moves over water is a waterspout.

Contents

Safety

Many, but not all funnel clouds will be warned for, and an appropriate warning may have been dispersed. Sirens (if present) may be sounding, Radio/TV may be interrupted for warning dissemination. If there is no warning, such as when outdoors, it is important to take immediate action.

If one spots a funnel cloud, it is recommended to take shelter immediately, as it may suddenly become a tornado. In the field, citizens are recommended to report or call-in funnel clouds to local police for relay to the National Weather Service (USA) or Environment Canada (CA)

If driving, determine if the funnel will pass near or through your intended route of travel. If so, stop and seek safe shelter at once, away from your vehicle, but not under any bridges/overpasses (see Tornado#Safety and Tornado#Myths and misconceptions).

Cold-air funnel clouds

Cold-air funnel clouds (vortices) are usually short-lived and generally much weaker than the vortices produced by supercells. Although cold-air funnels rarely make ground contact, they may touch down briefly and become weak tornadoes or waterspouts.

A shear funnel extending from a generic cumulus cloud. Observed in northern Texas by a member of the VORTEX project.

Unlike the related phenomenon associated with severe thunderstorms, cold-air funnels are generally associated with partly cloudy skies in the wake of cold fronts, where atmospheric instability and moisture is sufficient to support towering cumulus clouds but not precipitation. The mixing of cooler air in the lower troposphere with air flowing in a different direction in the middle troposphere causes the rotation on a horizontal axis, which, when deflected vertically by atmospheric conditions, can become a funnel cloud.[1]

They are a common sight along the Pacific Coast of the United States, particularly in the spring or autumn.[1]

See also

References

  1. ^ a b Cooley J. R., and M. E. Soderberg, 1973: Cold air funnel clouds. NOAA Tech. Memo. NWS CR-52, Scientific Services Division, NWS Central Region, Kansas City, MO, 29 pp.

External links


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • funnel cloud — noun A tapering cloud descending from a larger storm cloud, indicating the presence of an intense vortex. A tornado is a funnel cloud which reaches the ground. When we saw the funnel cloud, we headed for the basement …   Wiktionary

  • funnel cloud — a rapidly rotating funnel shaped cloud extending downward from the base of a cumulonimbus cloud, which, if it touches the surface of the earth, is a tornado or waterspout. Also called pendant cloud, tornado cloud, tuba. * * * …   Universalium

  • funnel cloud — fun′nel cloud n. mer a rapidly rotating funnel shaped cloud extending downward from the base of a cumulonimbus cloud, which, if it touches the surface of the earth, is a tornado or waterspout …   From formal English to slang

  • funnel cloud — noun Date: circa 1909 a funnel shaped cloud that projects from the base of a thundercloud and that often precedes the formation of a tornado; also tornado 2b …   New Collegiate Dictionary

  • funnel cloud — /ˈfʌnəl klaʊd/ (say funuhl klowd) noun a funnel shaped cloud formed from the core of a waterspout or tornado …   Australian English dictionary

  • funnel cloud — noun : a funnel shaped cloud that hangs below the greater thundercloud mass of a tornado …   Useful english dictionary

  • funnel cloud — A tornado, or vortex cloud, extending downward from the parent cloud but not reaching the ground …   Aviation dictionary

  • Funnel Cloud (album) — Infobox Album | Name = Funnel Cloud Type = Album Artist = Hem Released = September 5, 2006 Recorded = Genre = Folk rock Length = Label = Nettwerk Producer = Reviews = *Allmusic Rating|4|5 [http://www.allmusic.com/cg/amg.dll?p=amg… …   Wikipedia

  • Funnel (disambiguation) — The word funnel has several meanings.* A funnel is a conical device for channelling fluids or other substances into narrow openings. * The chimney of a ship is often called a funnel. * A funnel cloud (aloft) is a quickly rotating column of air… …   Wikipedia

  • Funnel — Trichterwolke Unter einer Trichterwolke, nach dem englischen Begriff auch Funnel bzw. Funnel cloud genannt, versteht man den sichtbaren Teil einer rotierenden Luftsäule mit einer mehr oder weniger vertikalen Rotationsachse. Sie erstreckt sich… …   Deutsch Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.