#WxGeekSpeak: Virga

The blog introduces you to a technical term from the American Meteorology Society’s “Glossary of Meteorology”. Welcome to #WxGeekSpeak!

Virga is common with storm systems during the Spring. Click the video above to find out why the raindrops from the clouds may never make it to your backyard.

Full definition of virga:

Wisps or streaks of water or ice particles falling out of a cloud but vaporizing before reaching the earth’s surface as precipitation.

Virga is frequently seen trailing from altocumulus and altostratus clouds, but also is discernible below the bases of high-level cumuliform clouds from which precipitation is falling into a dry subcloud layer. It typically exhibits a hooked form in which the streaks descend nearly vertically just under the precipitation source but appear to be almost horizontal at their lower extremities. Such curvature of virga can be produced simply by effects of strong vertical wind shear, but ordinarily it results from the fact that droplet or crystal vaporization decreases the particle terminal fall velocity near the ends of the streaks. Under some conditions, virga is associated with dry microbursts, which are formed as a product of the vaporization. 

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