Operational Utility of the Depth and Width of Three-Body Scatter Spikes

Prior studies have indicated that the presence of the three-body scatter spike (TBSS) signature is typically, though not always, associated with severe (≥ 1 in. or 2.54 cm in diameter) hail. Additional studies have noted that relating the presence of a TBSS to a specific hail size may not be possible. However, to our knowledge, no previous study has investigated how the depth and width of TBSSs may relate to resultant hail size or the potential for associated severe (≥ 50 kt or 58 mph) straight-line winds. Local studies of high-impact supercells have shown that storms producing both giant hail and significant straight-line winds are often associated with tall, broad TBSSs, which may be indicative of larger hail or a greater volume of large hail.

Here, we will present a multi-year climatology of TBSSs detected with the WSR-88D network across the northern plains region and compare the depth and width of each TBSS to associated hail and wind local storm reports. Correlations between TBSS characteristics and severe reports will be shown, and guidance in identifying and interpreting TBSSs during real-time warning operations will be provided. The ultimate goal is to determine the utility of the TBSS in estimating most likely hail sizes or straight-line wind speeds when crafting impact-based severe thunderstorm warnings.