the ascending air displacement from the waterfall and may go on to form other types of clouds such as cumulus cataractagenitus. Flammagenitus (flamma-/pertaining to fire) Formed by convection associated with large wildfires. Homogenitus (homo-/pertaining to humans) Formed as a result of human activities, particularly aircraft at high altitudes and heat-generating industrial activities at surface level. If a homogenitus cloud of one genus changes to another genus type, it is then termed a homomutatus cloud. Silvagenitus (silva-/pertaining to trees or forests) Formed by low-level condensation of water vapor released by vegetation, especially forest canopies. Mutatus mother clouds Nomenclature works the same way as for genitus mother clouds except for the mutatus suffix to indicate the complete rather than the partial transformation of the original cloud type. e.g. Altocumulomutatus – formed by the complete transformation of altocumulus mother cloud. The possible combinations of genera and mother clouds can be seen in this table. The genitus and mutatus clouds are each sorted from left to right in alphabetical order. The genus types and some sub-types are arranged from top to bottom in approximate descending order of average overall altitude range. Each box is marked where a particular genus or sub-type has a particular genitus or mutatus mother cloud. Informal terms recently accepted for WMO classification with Latin nomenclature Aviaticus cloud Persistent condensation trails (contrails) formed by ice crystals originating from water vapor emitted by aircraft engines. Usually resembles cirrus; recognized as a WMO genitus cloud cirrus homogenitus (man-made). Further transformation into cirrus, cirrocumulus, or cirrostratus homomutatus is possible depending on atmospheric stability and wind shear. Fallstreak hole Supercooled altocumulus or cirrocumulus distinguished by a hole with ragged edges and virga or wisps of cirrus. Accepted as a WMO supplementary feature to be named cavum (hole). Kelvin–Helmholtz cloud Crested wave-like clouds formed by wind-shear instability that may occur at any altitude in the troposphere. Accepted as a WMO supplementary feature with the Latin name fluctus. Pyrocumulus and Pyrocumulonimbus Cumulus and cumulonimbus clouds formed by quickly generated ground heat; including forest fires, volcanic eruptions and low level nuclear detonation. Accepted as a WMO genitus cloud with the Latin name flammagenitus, or homogenitus in the case of small cumulus formed by contained human activity. Roll cloud Elongated, low-level, tube shaped, horizontal formation not associated with a parent cloud. Accepted as a WMO stratocumulus or altocumulus species with the Latin name volutus. WMO and informal terms related