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Three-Body Scatter Spike
Here is a look at an interesting feature or artifact, from radar reflectivity.
This storm occurred on Feb 21, 2001, at ~ 550-620 pm, across portions of Dallas county.
This artifact is called a "Three-Body Scatter Spike". It is often an indicator of hail
(>2.5cm) or ~(1 in), in diameter. An excellent description, on how this occurs, is
presented by Zrni'c (1987), Wilson and Reum (1986 , 1988) and Lemon (1998).
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". This storm produced Nickel sized hail, along with wind damage
to roofs and knocked down several trees, in Safford, AL. The core of this storm was mainly over
rural sections of southern Dallas county, thus the largest hail from this storm was likely not
observed.
The Cross Section below, shows the "spike" on the right side of the image.
Here is what the Radar Observer would see when viewing this storm at 1.5 degree elevation.
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