One of the easiest ways to detect large hail on doppler radar is with the presence of a hail spike. The storm that produced large hail in East Hampton today showed several hail spikes at the time large hail was pelting down. Here’s a 3.1 degree base reflectivity scan from OKX at 20:41Z showing the hail size. The purple is DBZ >65. The hail spike is the light blue that extends downradial of the hail core.
Hail spikes, also known as Three Body Scatter Spikes, occur when the radar beam is deflected off a large object (hail in this case) down to the earth and then back to the hail stone and then finally back to the radar. Because the route of energy takes extra time the radar thinks there is something occuring further away from the radar than is actually the case. The narrow blue line extending northeast of the thunderstorm is the hail spike in this case.
Here’s a 2d cross section on a radial extending out from the OKX radar site. You can see the hail core suspended in the updraft with a hail spike extended on a radial on the radar beam downradial of the hail core. Awesome stuff!
While the largest “official” hail report we have is 0.88″ in East Hampton there was undoubtedly larger hail somewhere in town – possibly ping pong ball size!