Editing Funnel cloud

{{Short description|Funnel-shaped cloud not touching the ground}}
{{Redirect|Funnel Cloud|the Hem album|Funnel Cloud (album){{!}}''Funnel Cloud'' (album)}}

{{more citations needed|date=October 2012}}
[[File:Tornado skips and hops across the central Minnesota.jpg|right|thumb|A funnel cloud across the central Minnesota landscape as it lifted momentarily narrowly missing this rural farmstead.]]
[[File:F5 tornado funnel cloud Elie Manitoba 2007.jpg|300px|right|thumb|A needle-like funnel cloud, which may have been a tornadic circulation but was not yet visible as such and which did later develop to become an [[Fujita scale|F5]] [[2007 Elie tornado|tornado]], near [[Elie, Manitoba]]]]
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 cloud|cumulonimbus]] or [[Cumulus congestus cloud|towering]] [[cumulus cloud]]) but not reaching the ground or a water surface.<ref name="GoM">{{cite book |last = Glickman |first = Todd S. |title = Glossary of Meteorology |publisher = American Meteorological Society |edition = 2nd |date = 2000 |location = Boston 
|url = http://glossary.ametsoc.org/wiki/Funnel_cloud |isbn = 978-1878220349 }}</ref> 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]] [[thunderstorm]]s, and are often, but not always, a visual precursor to [[tornado]]es. Funnel clouds are visual phenomena, but these are not the [[vortex]] of [[wind]] itself.<ref name="NWS Glossary">{{cite web |url = https://forecast.weather.gov/glossary.php?word=FUNNEL%20CLOUD |title = Funnel cloud |website = National Weather Service Glossary  |publisher = NOAA National Weather Service |access-date = 2019-12-17  }}</ref>

=="Classic" funnel clouds==
If a funnel cloud touches the surface, the feature is considered a tornado, although ground level circulations begin before the visible condensation cloud appears. Most tornadoes begin as funnel clouds, but some funnel clouds do not make surface contact and these cannot be counted as tornadoes from the perspective of a naked eye observer, even as tornadic circulations of some [[Tornado intensity|intensity]] almost always are detectable when low-level [[Weather radar|radar]] observations are available. Also, tornadoes occur with some frequency without an associated [[condensation]] funnel. The term '''condensation funnel''' may refer to either a tornadic cloud or a funnel cloud aloft, but the term funnel cloud exclusively refers to a rotating condensation funnel not reaching the surface. If strong [[cyclone|cyclonic]] winds are occurring at the surface and are connected to a cloud base, regardless of condensation, then the feature is a tornado.<ref name="FAQ">{{cite web |url = https://www.spc.noaa.gov/faq/tornado/ |title =  What's the difference between a funnel cloud and a tornado? What is a funnel cloud? |last = Edwards |first = Roger |date = 19 April 2018 |website = The Online Tornado FAQ |publisher = NWS Storm Prediction Center |access-date = 2019-12-17 }}</ref>

Funnel clouds result from the low [[air pressure]]s found within tornadoes. The low air pressure causes air flowing towards the vortex to [[Adiabatic process#Adiabatic compression and expansion|expand and cool]]. If the air is sufficiently moist and cools to the [[dew point]], a funnel cloud is produced. The air pressure around the outer edge of the funnel cloud generally corresponds to the [[Lifted condensation level|air pressure]] of the [[cloud base]] of the parent cloud.<ref name="Stull">{{cite book |last1=Stull |first1=Roland |title=Practical Meteorology |date=2017 |publisher=University of British Columbia |isbn=978-0-88865-283-6 |url=https://geo.libretexts.org/Bookshelves/Meteorology_and_Climate_Science/Practical_Meteorology_(Stull)/15%3A_Thunderstorm_Hazards/15.03%3A_Section_4- |via=LibreTexts |access-date=30 January 2024 |chapter=15.4: Tornadoes}}</ref>

Debris swirls are usually evident prior to the condensation funnel reaching the surface. Some tornadoes may appear only as a debris swirl, with no obvious funnel cloud extending below the rotating cloud base at any time during the [[Tornadogenesis|tornadic life cycle]]. The surface level vortex tends to strengthen over time following initial formation, making the debris swirls and the condensation more apparent.<ref>{{Cite journal |last1=Varaksin |first1=Aleksey Yu |last2=Ryzhkov |first2=Sergei V. |date=October 2022 |title=Vortex Flows with Particles and Droplets (A Review) |journal=Symmetry |language=en |volume=14 |issue=10 |pages=2016 |doi=10.3390/sym14102016 |bibcode=2022Symm...14.2016V |issn=2073-8994 |doi-access=free }}</ref>

In cloud nomenclature, any funnel- or inverted-funnel-shaped cloud descending from cumulus or cumulonimbus clouds is technically described as an accessory feature called ''tuba''. The terms ''tuba'' and ''funnel cloud'' are nearly but not exactly synonymous; a [[wall cloud]], for example, is also a form of ''tuba''. Funnel clouds associated with supercells usually form within and under wall clouds.

==Cold-air funnel clouds==
Cold-air funnel clouds (vortices) are generally much weaker than the vortices produced by supercells. Although cold-air funnels rarely make ground contact, surface level vortices sometimes become strong enough for [[condensation]] cloud to "touch down" briefly, becoming visible as weak tornadoes or [[waterspout]]s. 
[[Image:Funnel cloud3 - NOAA.jpg|thumb|250px|right|A shear funnel extending from a [[cumulus humilis cloud]], which was observed in northern [[Texas]] during the first [[VORTEX projects|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 front]]s,<ref name="CC500L">{{cite journal |last = Davies |first = Jonathan M. |title = Tornadoes with Cold Core 500-mb Lows |journal = Weather and Forecasting|volume = 21 |issue = 6 |pages = 1051–1062 |date = 2006 |doi = 10.1175/WAF967.1 |bibcode = 2006WtFor..21.1051D |doi-access = free }}</ref> especially associated with certain [[low pressure system]]s, or in association with atmospheric boundaries such as [[lake breeze|lake]]<ref name="Cooley">{{cite journal |last = Cooley |first = Jack R. |title = Cold Air Funnel Clouds |journal = Monthly Weather Review|volume = 106 |issue = 9 |pages = 1368–1372 |date = 1978 |doi = 10.1175/1520-0493(1978)106<1368:CAFC>2.0.CO;2 |issn = 1520-0493 |bibcode = 1978MWRv..106.1368C |doi-access = free }}</ref> and [[sea breeze]]s or [[outflow boundary|outflow boundaries]].

The [[synoptic scale meteorology|larger scale]] weather conditions are characterized by particularly cold air aloft over relatively warmer low level air, leading to high [[lapse rate]]s, and often by high environmental [[vorticity]] yet relatively meager vertical [[wind shear]]. The funnels develop where [[atmospheric instability]] and moisture are sufficient to support towering cumulus clouds but typically limited to no or to little [[precipitation]]. Cold-air funnels, although weak, may persist for several minutes, and areas of intermittently forming funnel clouds may occur for tens of minutes.<ref>{{cite journal |last = Rauber |first = Robert M. |author2 = R. Scott |title = Central Illinois Cold Air Funnel Outbreak |journal = Monthly Weather Review|volume = 129 |issue = 11 |pages = 2815–2821 |date = 2001 |doi = 10.1175/1520-0493(2001)129<2815:CICAFO>2.0.CO;2 |issn = 1520-0493 |bibcode = 2001MWRv..129.2815R |doi-access = free }}</ref>

Multiple such areas of activity may form within the same region during afternoon heating. Cold-air funnels appears to be a diurnal phenomenon, weakening and eventually dissipating with loss of [[insolation|solar heating]]. When precipitation does develop, the associated [[downdraft]] tends to cause rapid demise of the cold-air funnels. 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 and tightened vertically by [[atmospheric convection|convective]] [[updraft]]s, forms a vertical rotation that can cause condensation to form a funnel cloud.<ref name="cooley_soderberg">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.</ref>

Cold-air funnel clouds are a common sight along the Pacific Coast of the United States, particularly in the spring or fall.<ref name="cooley_soderberg"/>

On July 29, 2013, a cold-core funnel cloud touched down as an EF0 tornado in [[Ottawa]], Ontario, Canada, causing extensive damage in the form of downed trees on a golf course. No advance weather watches or warnings were issued by Environment Canada, and the tornado was spawned from one of the few non-severe storm clouds moving through the area.<ref>{{cite web| url = https://www.cbc.ca/news/canada/ottawa/tornado-touched-down-in-ottawa-monday-1.1352888| title = Tornado touched down in Ottawa Monday {{!}} CBC News}}</ref><ref>{{cite web|url=https://ottawacitizen.com/news/Cold+core+funnels+give+Ottawa+commuters+twister+fright/8723402/story.html |title='Cold core funnels' give Ottawa commuters a twister fright |last=Lypny |first=Natascia |website=ottawacitizen.com |date=July 30, 2013 |access-date=August 2, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130801223936/http://www.ottawacitizen.com/news/Cold+core+funnels+give+Ottawa+commuters+twister+fright/8723402/story.html |archive-date=August 1, 2013 }}</ref>

==Other funnel clouds==
[[File:Small Shear Funnel in Carlyss Louisiana.jpg|thumb|Small shear funnel in Carlyss, Louisiana]]
Other funnel clouds include shear or "high based" funnels, which are ephemeral, small, and weak funnels associated with small cumulus clouds, often even those rooted aloft above the [[atmospheric boundary layer|boundary]] or surface layer, and in "fair weather" conditions.<ref name="high-based">{{cite journal |last = Bluestein |first = Howard B. |title = High-Based Funnel Clouds in the Southern Plains |journal = Monthly Weather Review|volume = 122  |issue = 11 |pages = 2631–2638 |date = 1994 |doi = 10.1175/1520-0493(1994)122<2631:hbfcit>2.0.co;2 |bibcode = 1994MWRv..122.2631B |doi-access = free }}</ref> Small funnel clouds, such as some occurring within vicinity of mountains, occur by unknown processes.<ref name="small funnels">{{cite journal  |last = Bluestein |first = Howard B. |title = More Observations of Small Funnel Clouds and Other Tubular Clouds |journal = Monthly Weather Review|volume = 133 |issue = 12 |pages = 3714–3720 |date = 2005 |doi = 10.1175/MWR3080.1 |bibcode = 2005MWRv..133.3714B |doi-access = free }}</ref>

Shear funnels might also occur with weak transient circulations at the cloud base of thunderstorms. Mesoanticyclones, which accompany [[mesocyclone]]s, often exhibit these funnel clouds. Brief funnels also are observed with some [[rear flank downdraft]]s (RFDs) (within [[inflow (meteorology)|inflow]] or [[outflow (meteorology)|outflow]] areas, and especially within inflow-outflow interchange areas as RFDs interact with mesocyclones or flanking line updrafts) and streamwise vorticity currents (SVCs) feeding into mesocyclones.

Although not considered a separate kind of funnel cloud, some funnel clouds form with [[mesovortices]] associated with [[squall line]]s, which also can become tornadoes but are often not visible as funnel clouds or tornadoes because they usually occur within obscuring precipitation. Other "fair weather" funnel clouds include [[horseshoe cloud]]s which are a very transient phenomena associated with extremely weak [[Horseshoe vortex|vortices]].

==See also==
* [[Dust devil]]
* [[Landspout]]
* [[Whirlwind]]

==References==
{{reflist|2}}

==External links==
{{Commons}}
* [http://www.flame.org/~cdoswell/atornado/atornado.html What is a tornado?] ([[Charles A. Doswell III]])
* [https://stormhighway.com/funnel_needs_to_touch_ground_to_be_tornado_myth.php Tornado Myths: A funnel cloud needs to touch the ground to be a tornado, OR the visible funnel is the tornado] (Dan Robinson)
* [https://www.usatoday.com/weather/wtkinds.htm ''USA Today'' article on small vortices]
* [https://web.archive.org/web/20051124092548/http://www.torro.org.uk/TORRO/severeweather/tornadofaqs.php TORRO Tornado FAQ]
* [https://web.archive.org/web/20070310222751/http://www.crh.noaa.gov/crnews/display_story.php?wfo=grr&storyid=3823 Cold-core waterspouts over Lake Michigan in fall 2006]
* [https://www.youtube.com/watch?v=Y6T1q0NP-kA news helicopter footage of cold-air funnel clouds in the St. Louis metropolitan area in spring 2007] ([[KTVI]])
* {{cite journal |last= Bluestein |first = Howard B. |author-link= Howard B. Bluestein |title= A Funnel Cloud in a Convective Cloud Line to the Rear of a Surface Cold Front |journal= [[Monthly Weather Review]] |volume= 136 |issue= 7 |pages= 2786–95 |date=July 2008 |doi= 10.1175/2007MWR2357.1 |bibcode = 2008MWRv..136.2786B |doi-access= free }}

{{cloud types}}
{{Cyclones}}

[[Category:Accessory clouds]]
[[Category:Cumulus]]
[[Category:Tornado]]
[[Category:Tornadogenesis]]
[[Category:Microscale meteorology]]