In meteorology, what is "virga"?

In meteorology, a virga is an observable streak or shaft of precipitation falling from a cloud that evaporates or sublimates before reaching the ground.

A virga often appears in streaks or shafts extending from the bottoms of clouds. You often see virga over a desert, where low humidity and high temperatures can cause rain to evaporate shortly after being released by clouds. Or you might see virga at high altitudes; in fact, the precipitation often starts out in the form of ice crystals. Virga is commonly seen in the U.S. West and above the Canadian Prairies, in the Middle East, Australia, and North Africa.

Virga can lead to the development of microbursts, which pose a dangerous threat to planes and aircraft. These microbursts come about as rainfall transitions back into water vapor, removing heat from the air and causing an accelerating sink of colder air, which can cause severe turbulence.

A virga is often referred to as a 'jellyfish cloud' based on its puffy-top appearance with streaky stingers hanging below. Apart from jellyfish though, they are often spotted looking like various objects in the sky.

As a supplementary cloud feature, they occur most frequently with Cirrocumulus, Altocumulus, Altostratus, Nimbostratus, Stratocumulus, Cumulus, and Cumulonimbus.

The word virga is derived from Latin meaning “twig” or “branch”.

Observing a virga is an especially dramatic sight at sunrise or sunset.