What is virga?

Virga refers specifically to the phenomenon where rain falls from a cloud but evaporates before it reaches the ground. This occurs because the air below the cloud is drier and has lower humidity, causing the moisture to vaporize as it descends. As a result, observers may see streaks of precipitation that appear to be falling but do not actually make contact with the earth. This is often encountered in arid regions and can be associated with certain cloud types that produce precipitation.

The other options describe different meteorological concepts. While a type of thunderstorm can produce rain, it is not synonymous with virga. Severe weather conditions can be indicated by various signs, but virga itself does not serve as a direct indicator of severity. High-altitude clouds, while important in weather patterns, are not a definition of virga. Virga is distinct in that it specifically focuses on the process of evaporation of rain before it reaches the ground, highlighting its unique characteristics in the study of weather phenomena.