NWS Radar Hail Spike

NWS Doppler Radar (WSR-88D) Example Products

Base reflectivity data at 0.5 degree elevation angle from the KLVX WSR-88D Doppler Radar. Reflectivity shows where and how hard it is raining or snowing, as well as precipitation intensity trends and movement. Blue and green colors represent light-to-moderate rainfall. Yellow and orange colors show moderate-to-heavy precipitation, while red is very heavy rainfall and pink and blue colors inside the red color represent hail of different sizes.

At left is a close-in view of a supercell thunderstorm over central Kentucky on March 2, 2012. The storm produced very large hail (golf ball to baseball size in diameter). Note to the south-southwest of the hail core is an elongated axis of weak returns (blue color). This axis is "down-radial" from the hail core. This is called a three-body scatter spike (TBSS), or hail spike, and is an indication that large hail is contained in the thunderstorm. However, the TBSS signature itself is not real, i.e., it is not raining where the spike is. Instead, it is an erroneous return of weak energy back to the radar after the original beam of energy from the radar hits the large hail in the storm.

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