Editing Wall cloud (section)

== Structure ==
Wall clouds can be anywhere from a fraction of {{convert|1|mi|km|1|abbr=on}} wide to over {{convert|5|mi|km|0|abbr=on}} across. Wall clouds form in the inflow region, on the side of the storm coinciding with the direction of the steering winds (deep layer winds through the height of the storm). In the Northern Hemisphere wall clouds typically form at the south or southwest end of a supercell. This is in the rear of the supercell near the main updraft and most supercells move in a direction with northeasterly components, for supercells forming in northwest flow situations and moving southeastward, the wall cloud may be found on the northwest or back side of such storms. Rotating wall clouds are visual evidence of a mesocyclone.

=== Associated features ===
[[File:Wall Cloud in NE Colorado.jpg|thumb|left|A wall cloud with '''tail cloud'''.]]
Some wall clouds have a feature similar to an "eye", as in a [[mesoscale convective vortex]].

Attached to many wall clouds, especially in moist environments, is a '''cauda'''<ref name=ICA2017/> ('''tail cloud'''), a tail-like band of cloud extending from the wall cloud toward the [[precipitation]] core.<ref name=":0">{{Cite web |date=July 20, 2021 |title=Cauda &#124; International Cloud Atlas |url=https://cloudatlas.wmo.int/en/clouds-supplementary-features-cauda.html |archive-url=https://web.archive.org/web/20210720112818/https://cloudatlas.wmo.int/en/clouds-supplementary-features-cauda.html |archive-date=2021-07-20}}</ref> It can be thought of as an extension of the wall cloud in that the tail cloud is connected to the wall cloud and condensation forms for a similar reason.{{Citation needed|date=July 2024}} Cloud elements may be seen to be moving into the wall cloud, as it is also an inflow feature.<ref name=":0" /> Most movement is horizontal, but some rising motion is also often apparent at the junction between the tail cloud and the wall cloud.<ref name=":0" />

Some wall clouds also have a band of cloud fragments encircling the top of the wall cloud where it meets the ambient cloud base; this feature is a '''collar cloud'''.<ref>{{cite book |last = Branick |first = Michael L. |title = NOAA Technical Memorandum NWS SR-145: A Comprehensive Glossary of Weather Terms for Storm Spotters |publisher = National Weather Service |date = 1996 |url = http://www.srh.noaa.gov/oun/?n=spotterglossary2#Collar%20Cloud |oclc = 39732655 }}</ref>

Another accessory cloud is the '''flumen''', commonly known as the '''beaver's tail'''.<ref name="ICA2017" /> It is formed by the warm, humid [[inflow (meteorology)|inflow]] of a strong thunderstorm, and is often mistaken for tornadoes.<ref name="ICA2017" /> Although the presence of a flumen is associated with tornado risk,{{Citation needed|date=July 2024}} the flumen does not rotate.<ref name="ICA2017" />

=== Wall cloud vs. shelf cloud ===
[[File:Rolling-thunder-cloud.jpg|thumb|left|A shelf cloud over [[Enschede]], [[Netherlands]]]]
Many storms contain [[shelf cloud]]s, which are often mistaken for wall clouds since an approaching shelf cloud appears to form a wall made of clouds and may contain turbulent motions.<ref name="Training"/> Wall clouds are inflow clouds and tend to slope inward, or toward the precipitation area of a storm. Shelf clouds, on the other hand, are [[outflow (meteorology)|outflow]] clouds that jut outward from the storm, often as [[gust front]]s. Also, shelf clouds tend to move outward away from the precipitation area of a storm.

Shelf clouds most often appear on the leading edge of a thunderstorm as they are formed by condensation from the cool outflow of the storm that lifts warmer air in the ambient environment (at the [[outflow boundary]]). When present in a supercell thunderstorm these shelf clouds on the leading edge of a storm are associated with the [[forward flank downdraft]] (FFD). Shelf clouds in supercells also form with the [[rear flank downdraft]] (RFD), although these tend to be more transitory and smaller than shelf clouds on the forward side of a storm.<ref>{{cite web |last = Drummond |first = David |title = Advanced Module |work = Skywarn Storm Spotter Guides |url = http://spotterguides.us/advanced/advanced06.htm |access-date = 2014-06-01 |archive-url =https://web.archive.org/web/20040111050931/http://spotterguides.us/advanced/advanced06.htm|url-status = dead |archive-date =2004-01-11}}</ref><ref>{{cite web |title = The Tornado |work = Thunderstorms and Severe Weather |publisher = the University of Texas |date = 29 Jun 1998 |url = http://www.tsgc.utexas.edu/stars/tornado.html |access-date = 2014-06-01 }}</ref> A wall cloud will usually be at the rear of the storm, though small, rotating wall clouds (a feature of a [[mesovortices|mesovortex]]) can occur within the leading edge (typically of a quasi-linear convective system (QLCS) or [[squall line]]) on rare occasion.<ref name="Training">Chance Hayes, National Weather Service Wichita, Kansas. "Storm Fury on the Plains." Storm Spotter Training. 4H Building, Salina, Kansas. 22 Feb. 2010. Lecture.</ref> 
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