Spotting A Hail Core With Radar

As of this writing, there is a pretty large thunderstorm affecting portions of Montana. I’m going to use this storm to show you how meteorologists monitor radar for the development of hail.

So, the above image is your basic base reflectivity image. This is what you generally see posted on social media, or what you see local television meteorologists use.

Above is the same image, however I have circled a region of the radar that is indicative of large hail. This is called a Three Body Scatter Spike. It is as a result of the radar beam being reflected and refracted by the large hail. Look at the below figure for a better idea.

The above image is a 2D slice through the radar. Using this, you can tell how high the precipitation is in a thunderstorm. Where the white and purple is, there is large hail. The higher the hail core extends, the more robust the updraft is, which means the hail is larger. Notice the hail core extends to over 20,000 feet! Below is just a 3 dimensional rendering of the image above. This gives you a better idea of the large size of the hail core.

Using everything above, we can get an estimate of the maximum hail size. There appear to be two hail cores in the thunderstorm. The one on the east side has an estimated hail size of 3.12″ and the hail core on the west has an estimated hail size of 1.21″