Editing Funnel cloud (section)

==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>