A theory that has been worked on at TheWeatherSpace.com by Meteorologist Kevin Martin since July 24th may explain why some hailstones are large like in Aurora and Vivian. The theory comes from looking at the systems around the main producer.
"I decided to look back at the radar images and compare the surrounding area, the way the jet was moving, and how it interacted with the local storm environment", said Martin. "I believe hailstones of greater size like Vivian, SD and Aurora, NE are not generated by one single storm, but multiple updrafts."
Martin states that his theory cannot fully be proven and it is just a hypothesis at the moment.
According to the theory, hailstones in both hail events in 2003 and 2010 were found on the tail-end system out of a cluster of three very powerful thunderstorms. If Martin's theory is correct, a select few may actually jump from one updraft to the other, which would explain why a few only make it to the larger size while others in the same updraft are 1/2 the size.