Dual-pol

The radar sending both horizontal and vertical pulses, which is what makes CC and ZDR possible. Rolled out across the network around 2012.

Related

CC (correlation coefficient) Whether everything in the beam looks alike. High for rain, low for a mix — hail, melting snow, or tornado debris.
ZDR (differential reflectivity) How flat the things in the beam are. Positive for raindrops, near zero for tumbling hail.

See it on real storms: open the radar, or read reading the radar.