It makes for pretty pictures and maybe even a conversation starter in the car - much like many drives with your family and friends, I'm sure at some point you look up in the sky and wonder, how does that happen? The conversation starter today? Virga. In its simplest form, it's rain falling from a cloud but it's evaporating before it hits the ground. Image 1 is a picture of Virga courtesy NC State University. In it you see a cloud with some 'stuff" coming out of the bottom. They look like thin gray streaks stretching down towards Earth. We identify that "stuff" as virga. It almost looks like someone took a pencil and started erasing the cloud. Another way virga forms is a result of a strong updraft. These are winds associated with a strong thunderstorm. If the winds are blowing into the storm faster than the rain falling, the result - virga.
In the second image I highlighted exactly what I'm referencing. See it now? Technically it's raining in the circled area, but because the air is so warm below the base of the cloud, it's evaporating before it reaches the ground. In some instances, it will show up on our Live First Alert Doppler Radar as rain. And that my friends, can make it tricky to determine whether it's indeed rain or virga. How do we know either way? One way is by your pictures. As stated earlier, these types of clouds make for pretty portraits. Another way to determine if the "rain" is reaching the ground, is knowing the type of air mass at the surface. If it's a very warm air mass and the radar returns are representing very light rain - it may be safe to assume the rain is not reaching the ground. Of course, if there's a weather observation station near this particular cloud, this would be yet another way to help us decipher rain vs. virga.
I hope you learned something new today! Have a weather question? Feel free to e-mail me and it may be featured in a blog post soon!
As always, thanks for connecting and watching WLBT!