PITTSBURGH — Western Pennsylvania is no stranger to hail. From April to August, Pittsburgh sees roughly 2,400 hail reports with records dating 1955-2019. The peak month of hail reports for the city is June with 635 reports. Large hail reports are gathered by the National Weather Service and are classified as three-quarter inch or larger. Severe thunderstorm warnings are issued for storms that contain hail of one inch or larger.
Luckily, for western Pennsylvania, we don’t see giant hail of two inches or larger very often. In March 2020, a severe thunderstorm dropped hail the size of tennis balls which is 2.5 inches in diameter. Prior to that, there had only been three other times that hail of 2 inches or larger had been reported in the WPXI viewing area in March. Also prior to that event, there had only been 40 reports of 2 inch or larger hail in western Pennsylvania since 1950.
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The largest hail ever reported in our area was 4.5 inches in Beaver County. In happened near Beaver Falls on July 26, 1956.
Larger hail stones can generate what we call three-body scatter spikes on radar. Here’s a look at a radar image of a tornadic-supercell thunderstorm in north Texas on April 27, 2021.
You can see that green line that is coming out the back or left side of the storm toward Guthrie, TX (the storm was moving east). This green line represents the three-body scatter spike. In meteorology, this is caused by the radar beam going out and hitting the large hail aloft in the storm, that energy scattering back to the ground, and then back up to the hail and then to the radar. The radar then displays it as a green line even though no precipitation is falling there.
Stay with Severe Weather Team 11 as we track storms through spring and summer.
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