During the late afternoon and early evening hours of 23
July 2010, thunderstorms developed over portions of central South Dakota.
Several storms quickly became severe in an environment favorable for supercell
thunderstorms. In particular, one very strong supercell thunderstorm
moved southeastward across portions of Stanley, Jones, and Lyman
counties. One of the hardest hit locations was the community of
Vivian, South Dakota, where extremely large hail, destructive winds to 80
mph, and a brief tornado were reported.
A record setting hailstone was ultimately discovered in
Vivian, measuring 8.0 inches in diameter, 18.625 inches in circumference, and
weighing in at an amazing 1.9375 pounds!! This hailstone broke the
previous United States hail size record for diameter (7.0 inches -
22 June 2003 in Aurora, NE) and weight (1.67 pounds - 3 September
1970 in Coffeyvile, KS). The Aurora, Nebraska hailstone will
retain the record for circumference (18.75 inches).
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The hailstone's
official record dimensions were as of the time personnel from the NWS in
Aberdeen first observed and measured it. The stone
did shrink considerably (melting and sublimation) between impact and when it
was first measured by NWS personnel due in part to a
power outage at the residence of the individual who found the stone.
It should also be noted that many other stones with diameters exceeding 6
inches were also noted during the storm survey!
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| Diameter of Vivian, SD hailstone being measured. |
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