Editing Cloud (section)

====Unstable or mostly unstable====
More general airmass instability in the troposphere tends to produce clouds of the more freely convective cumulus genus type, whose species are mainly indicators of degrees of atmospheric instability and resultant vertical development of the clouds. A cumulus cloud initially forms in the low level of the troposphere as a cloudlet of the species ''humilis'' that shows only slight vertical development. If the air becomes more unstable, the cloud tends to grow vertically into the species ''mediocris'', then strongly convective ''congestus'', the tallest cumulus species<ref name="species" /> which is the same type that the International Civil Aviation Organization refers to as 'towering cumulus'.<ref name="automated Cb and Tcu detection" />

[[File:Cumulus mediocris atmospheric instability 01.jpg|thumb|Cumulus mediocris cloud, about to turn into a cumulus congestus]]
With highly unstable atmospheric conditions, large cumulus may continue to grow into even more strongly convective cumulonimbus ''calvus'' (essentially a very tall congestus cloud that produces thunder), then ultimately into the species ''capillatus'' when supercooled water droplets at the top of the cloud turn into ice crystals giving it a cirriform appearance.<ref name="species" /><ref name="clouds - species and varieties">{{Cite web |last=Boyd, Sylke |year=2008 |title=Clouds – Species and Varieties |url=http://www.morris.umn.edu/~sboyd/weather/cloudsystems/Clouds_files/speciesandvarieties.htm |url-status=dead |archive-url=https://web.archive.org/web/20101230041442/http://www.morris.umn.edu/~sboyd/weather/cloudsystems/Clouds_files/speciesandvarieties.htm |archive-date=30 December 2010 |access-date=4 February 2012 |website=University of Minnesota}}</ref>