The Radar 'Three-Body Scatter Spike': An Operational Large-Hail Signature

Recently, a rare radar artifact called the “flare echo” or “three-body scatter signature” has been examined by several researchers. Here, this midlevel storm signature is called the “three-body scatter spike” (TBSS) and is examined in detail for some severe storms scanned by operational WSR-88Ds. The TBSS is a generally 10–30-km long region of echo aligned radially downrange from a highly reflective (>63 dBZ) echo core. It is found almost exclusively aloft and is characterized by low reflectivity and is usually characterized by near-zero or weak inbound velocities. Spectrum widths are very broad and often noise like. The aforementioned research concluded that it is caused by non-Rayleigh radar microwave scattering (Mie scattering) from a region of large hydrometeors; most likely large, wet hail. This conclusion is supported and expanded upon. WSR-88D data are presented concerning a storm attended by a TBSS that produced giant (>5 cm) hail and violent surface winds. In this case, the three-body si...