Severe hail-producing thunderstorms erupted across parts of north central Kansas on Saturday evening, June 6, 2009. One of the strongest storms developed near Beloit, Kansas, then moved northeast toward Scottsville in far northeast Mitchell County. Golf ball size hail was reported in Scottsville at 10:12 PM with this storm.
The radar reflectivity image below (click to enlarge) depicts the storm over Scottsville at 10:10 PM. In this image we are actually looking into the storm at approximately 15,500 feet above ground level (AGL), with the radar itself located 60 miles northwest of Scottsville, near Blue Hill, Nebraska. The purple shading in the core of the storm shows very high levels of reflectivty around 70 decibels (dBZ), with values this high often a good indicator of hail within a storm.
Of particular interest is the long "spike" of reflectivity extending to the southeast of the storm into Cloud County. In fact, this "spike" is not a reflection of actual precipitation in the area, but instead is a classic example of a radar artifact known as a "Three-Body Scatter Spike", or TBSS. The presence of a TBSS almost always indicates that a storm contains large hail. In simple terms, a TBSS is caused by the radar beam hitting the hail aloft, scattering to the ground below, then scattering back upward, and finally being scattered once again by the hail aloft. The 3 scatterings illustrate the triple reflection, thus the term "three-body scatter spike".
For more information on a TBSS, please visit the following site: http://www.srh.noaa.gov/bmx/significant_events/research/3body/index.php
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