The "prize winning" hailstone measured 8.0 inches in diameter and 18.625 inches in circumference. It weighed in at nearly 2 pounds (1.9375 lbs. to be exact).
It is estimated that the updraft (upward wind motion) within the thunderstorm that produced the hail was traveling at speeds of 160-180 mph. With that in mind, and considering the fact that the hailstone weighed nearly 2 pounds, it likely fell to earth at a speed of nearly 150 mph!
Below is a picture of the divot left in the ground by the record producing stone:
Needless to say, damage around the Vivian area was extreme. Take a look at the photos below:
Yes, you're seeing the last photo correctly...it was taken on the inside of a home near Vivian, where a hailstone crashed right through the roof and ceiling, landing in the living room!
Below is a 4-panel image of the Aberdeen, SD NEXRAD radar as the storm approached Vivian. From upper left to lower right, the images show reflectivity (precipitation echoes such as rain and, of course, hail) at elevations of 0.5 degrees (approximately 16,000 feet above ground level), 0.9 degrees (21,000 ft. AGL), 1.3 degrees (27,500 ft. AGL) and 1.8 degrees (33,000 ft. AGL):
Storm chaser Chad Cowan captured some amazing photos of the structure of this storm. Go to his website here to take a look.
The previous record-holding hailstone by diameter was captured near Aurora, NE on June 22, 2003 at 7 inches in diameter. The previous record holding stone by weight was captured in Coffeyville, KS on September 3, 1970, weighing in at 1.67 pounds.
It should be noted that considerable melting took place on the Vivian stone before NWS employees were able to measure and weigh it. That means the actual record setting values were probably quite a bit higher!