L is for....

Layer Clouds
Clouds of no marked vertical development, known as "sheet clouds" as opposed to "heap clouds". Cirrus, stratocumulus and stratus are all examples of layer clouds. For more cloud descriptions see "C is for clouds."

Lenticularis
A term applied mainly to certain types of altocumulus, stratocumulus and cirrocumulus clouds which have the shape of lenses or almonds. This type of cloud usually (but not always) appears in regions of marked orography (e.g. near mountain ranges).

Lightning

Lightning strikes!

A visible electric discharge associated with a thunderstorm.

Various types of lightning flash occur including "cloud discharge" (within the thunder cloud), "air discharge" (between the cloud and adjacent air) and "ground discharge" between the cloud and the ground.

Studies have shown that the ground discharge consists of at least two "strokes" or "streamers". The "leader stroke" from cloud to ground is relatively faint and takes a fraction of a second, progressing in steps with many branches spreading out from it.

This is followed by an immediate "return stroke" from ground to cloud which is extremely rapid and illuminates the main channel and branches.

Low
A term commonly used to denote an area of low pressure. See also "depression" in the "D is for…" section.