Editing Tornado (section)

== Definitions ==
A tornado is a violently rotating column of air, in contact with the ground, either pendant from a [[cumuliform cloud]] or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud.<ref name="Glossary of Meteorology">{{cite book|url=https://glossary.ametsoc.org/wiki/Tornado|title=Tornado|author=Glossary of Meteorology|edition=2|access-date=2021-03-06|publisher=American Meteorological Society|year=2020|archive-date=2021-05-08|archive-url=https://web.archive.org/web/20210508191421/https://glossary.ametsoc.org/wiki/Tornado|url-status=live}}</ref> For a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base. The term is not precisely defined; for example, there is disagreement as to whether separate touchdowns of the same funnel constitute separate tornadoes.<ref name="SPC FAQ"/> ''Tornado'' refers to the [[vortex]] of wind, not the condensation cloud.<ref name="Advanced Spotter Guide"/><ref name="tornado?">{{cite web|first=Charles A. III|last=Doswell|url=http://www.cimms.ou.edu/~doswell/a_tornado/atornado.html|title=What is a tornado?|access-date=2008-05-28|publisher=Cooperative Institute for Mesoscale Meteorological Studies|date=2001-10-01|archive-date=2018-07-03|archive-url=https://web.archive.org/web/20180703163826/http://www.cimms.ou.edu/~doswell/a_tornado/atornado.html|url-status=live}}</ref>

=== Funnel cloud ===
{{Main|Funnel cloud}}
[[File:A tornado near Anadarko, Oklahoma, on May 3, 1999.jpg|thumb|upright=1.35|A tornado near [[Anadarko, Oklahoma]], 1999. The ''funnel'' is the thin tube reaching from the cloud to the ground. The lower part of this tornado is surrounded by a [[transparency (optics)|translucent]] dust cloud, kicked up by the tornado's strong winds at the surface. The wind of the tornado has a much wider radius than the funnel itself.]]
A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds (as described by [[Bernoulli's principle]]) and rapid rotation (due to [[cyclostrophic balance]]) usually cause [[water vapor]] in the air to condense into cloud droplets due to [[adiabatic cooling]]. This results in the formation of a visible funnel cloud or condensation funnel.<ref name="Renno">{{cite journal |first=Nilton O.|last=Renno |title=A thermodynamically general theory for convective vortices |journal=[[Tellus A]] |volume=60 |issue=4 |pages=688–99 |date=2008-07-03 |url=http://vortexengine.ca/misc/Renno_2008.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://vortexengine.ca/misc/Renno_2008.pdf |archive-date=2022-10-09 |url-status=live |doi=10.1111/j.1600-0870.2008.00331.x |access-date=2009-12-12 |bibcode=2008TellA..60..688R |hdl=2027.42/73164 |hdl-access=free }}</ref>

There is some disagreement over the definition of a funnel cloud and a condensation funnel. According to the ''Glossary of Meteorology'', a funnel cloud is any rotating cloud pendant from a cumulus or cumulonimbus, and thus most tornadoes are included under this definition.<ref>{{cite book |url=http://glossary.ametsoc.org/index.php?title=Special:AllPages/F |title=Funnel cloud |date=2000-06-30 |publisher=[[American Meteorological Society]] |edition=2 |access-date=2009-02-25 |archive-url=https://web.archive.org/web/20130205095929/http://glossary.ametsoc.org/index.php?title=Special%3AAllPages%2FF |archive-date=2013-02-05 |url-status=dead}}</ref> Among many meteorologists, the "funnel cloud" term is strictly defined as a rotating cloud which is not associated with strong winds at the surface, and condensation funnel is a broad term for any rotating cloud below a cumuliform cloud.<ref name="SPC FAQ"/>

Tornadoes often begin as funnel clouds with no associated strong winds at the surface, and not all funnel clouds evolve into tornadoes. Most tornadoes produce strong winds at the surface while the visible funnel is still above the ground, so it is difficult to discern the difference between a funnel cloud and a tornado from a distance.<ref name="SPC FAQ"/>

===Outbreaks and families===
{{Main|Tornado family|tornado outbreak|tornado outbreak sequence}}
Occasionally, a single storm will produce more than one tornado, either simultaneously or in succession. Multiple tornadoes produced by the same [[storm cell]] are referred to as a "tornado family".<ref>{{cite web|url=http://www.srh.noaa.gov/oun/severewx/glossary4.php#t|title=A Comprehensive Glossary of Weather Terms for Storm Spotters|access-date=2007-02-27|first=Michael|last=Branick|year=2006|publisher=National Oceanic and Atmospheric Administration |archive-url=https://web.archive.org/web/20030803230231/http://www.srh.noaa.gov/oun/severewx/glossary4.php#t |archive-date=2003-08-03}}</ref> Several tornadoes are sometimes spawned from the same large-scale storm system. If there is no break in activity, this is considered a tornado outbreak (although the term "tornado outbreak" has various definitions). A period of several successive days with tornado outbreaks in the same general area (spawned by multiple weather systems) is a tornado outbreak sequence, occasionally called an extended tornado outbreak.<ref name="Glossary of Meteorology"/><ref name="significant tornadoes"/><ref>{{cite web|url=http://ams.confex.com/ams/pdfpapers/81933.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://ams.confex.com/ams/pdfpapers/81933.pdf |archive-date=2022-10-09 |url-status=live|title=Tornado Outbreak Day Sequences: Historic Events and Climatology (1875–2003)|access-date=2007-03-20|first1=Russell S. |last1=Schneider |first2=Harold E. |last2=Brooks |first3=Joseph T. |last3=Schaefer  |name-list-style=amp |year=2004}}</ref>