What does the presence of virga under a cloud usually indicate?

The presence of virga, which refers to streaks of rain that evaporate before reaching the ground, typically indicates strong downdrafts associated with a cloud. When rainfall occurs under a cloud, and falls as virga, it suggests that the precipitation is being pulled downward rapidly by a column of sinking air, characteristic of strong downdrafts.

This phenomenon usually occurs when the air beneath the cloud is relatively dry, which allows the rain to evaporate before it reaches the surface. The evaporation of rain can happen due to the presence of cool, dry air below the cloud, intensified by the downward movement of air packed with moisture, thus creating the visible streaks of virga.

Understanding the dynamics of virga is important for pilots because it can indicate turbulence and changing weather conditions. It often points to a potential for sudden downdrafts or turbulence in the vicinity of the cloud, which is critical information for flight safety and navigation.