Editing Cloud (section)

====Multi-level or moderate vertical====
[[File:Nimbostratus virga.JPG|thumb|Nimbostratus with virga]]
These clouds have low- to mid-level bases that form anywhere from near the surface to about {{convert|8000|ft|abbr=on|order=flip|-2}} and tops that can extend into the mid-altitude range and sometimes higher in the case of nimbostratus.
* Genus [[nimbostratus]] (Ns) – This is a diffuse, dark gray, multi-level stratiform layer with great horizontal extent and usually moderate to deep vertical development that looks feebly illuminated from the inside.<ref name="nimbostratus">{{Cite web |year=2017 |editor-last=World Meteorological Organization |title=Nimbostratus, International Cloud Atlas |url=https://cloudatlas.wmo.int/clouds-genera-nimbostratus.html |access-date=16 May 2017}}</ref> Nimbostratus normally forms from mid-level altostratus, and develops at least moderate vertical extent<ref name="cloud atlas" /><ref name="Plymouth State Meteorology" /> when the base subsides into the low level during precipitation that can reach moderate to heavy intensity. It achieves even greater vertical development when it simultaneously grows upward into the high level due to large-scale frontal or cyclonic lift.<ref name="glossary">{{Cite web |last=American Meteorological Society |year=2012 |title=Glossary of Meteorology |url=http://glossary.ametsoc.org/wiki/Nimbostratus |access-date=9 January 2014}}</ref> The ''nimbo-'' prefix refers to its ability to produce continuous rain or snow over a wide area, especially ahead of a warm front.<ref name="precipitating clouds">[[#Ackerman|Ackerman]], p. 118</ref> This thick cloud layer lacks any towering structure of its own, but may be accompanied by embedded towering cumuliform or cumulonimbiform types.<ref name="Plymouth State Meteorology" /><ref name="nimbostratus associated with deep convection">{{Cite book |last=Houze, Robert A. |url=https://books.google.com/books?id=5DKWGZwBBEYC&pg=PA211 |title=Cloud Dynamics |publisher=Academic Press |year=1994 |isbn=978-0-08-050210-6 |page=211}}</ref> Meteorologists affiliated with the [[World Meteorological Organization]] (WMO) officially classify nimbostratus as mid-level for synoptic purposes while informally characterizing it as multi-level.<ref name="Definitions" /> Independent meteorologists and educators appear split between those who largely follow the WMO model<ref name="cloud atlas">{{Cite web |last=Clouds Online |year=2012 |title=Cloud Atlas |url=http://www.clouds-online.com |access-date=1 February 2012}}</ref><ref name="Plymouth State Meteorology">{{Cite web |last=Koermer, Jim |year=2011 |title=Plymouth State Meteorology Program Cloud Boutique |url=http://vortex.plymouth.edu/cloudboutique/ |url-status=dead |archive-url=https://web.archive.org/web/20140701173917/http://vortex.plymouth.edu/cloudboutique/ |archive-date=1 July 2014 |access-date=1 September 2015 |publisher=[[Plymouth State University]]}}</ref> and those who classify nimbostratus as low-level, despite its considerable vertical extent and its usual initial formation in the middle altitude range.<ref>{{Cite web |last=Hatheway, Becca |year=2009 |title=Cloud Types |url=http://www.windows2universe.org/earth/Atmosphere/clouds/cloud_types.html |access-date=15 September 2011 |website=Windows to the Universe, US National Earth Science Teachers Association (NESTA)}}</ref><ref name="classification of clouds">{{Cite web |title=cloud: Classification of Clouds |url=http://www.infoplease.com/ce6/weather/A0857400.html |website=Infoplease.com}}</ref>
* Species [[cumulus mediocris]] – These cumuliform clouds of free convection have clear-cut, medium-gray, flat bases and white, domed tops in the form of small sproutings and generally do not produce precipitation.<ref name="cumulus" /> They usually form in the low level of the troposphere except during conditions of very low relative humidity, when the cloud bases can rise into the middle-altitude range. Cumulus mediocris is officially classified as low-level and more informally characterized as having moderate vertical extent that can involve more than one altitude level.<ref name="Definitions" />