ProForecasters's Blog

From EAX

Large Hail in the Northland the Evening of June 15, 2008

While much of the widespread thunderstorm activity took place during the daytime hours of the 15th.  One very powerful supercell thunderstorm developed near Leavenworth, KS and tracked eastward near the Kansas City International Airport, and further east towards Kearney, Liberty, and Richmond.  Since the moment it developed, this storm exhibited some of the classic signals of producing very large hail, including a very powerful updraft of air, high reflectivity values, and modest rotation in the mid-level of the storm.  Some of the largest hail reported in this storm was around 2.75 inches near Leavenworth, KS and 2.25" near Kearney, MO.  Due to the very strong upwards motion of the storm, large hail was actually thrown out of the storms and landed in places where the skies were still blue!

As you can see in the images below, the signature of hail can also be seen in radar imagery.  A typical large hail indicator is called a "three body scatter spike" (TBSS) or the appearance of a beam of reflectivity away from the storm.  In brief, simple terms, this is caused by the radar beam hitting the wet hail, 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".  In cases of extremely large hail, this TBSS can be seen in many layers of the atmosphere as evident in the pictures below which show 4 different levels of the storm as sampled by radar.  For more information on a TBSS, please visit the following site: http://www.srh.noaa.gov/bmx/significant_events/researc
h/3body/index.php 

For additional information on how large hail is produced, please visit the NWS Jetstream page on large hail, found here

Radar Imagery ~8:50 PM Radar Imagery ~9:35 PM (top and bottom) Several Multi-Level Radar Views of Northland Hail Producing Supercell and TBSS

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Hail Pictures

Various Hail Pictures From Leavenworth, KS and Kearney, MO