Characterization and Analysis of Hailstorms in the Northern Great Plains

Hail is a meteorological occurrence that appears frequently during spring and summer across the Northern Great Plains. This paper first characterizes patterns associated with reported hail events occurring within a five-state region (North Dakota, Minnesota, South Dakota, Iowa, and Nebraska) from 2000-2006 using records taken from the National Climatic Data Center (NCDC) Severe Storms database. Patterns of interest include the seasonality of hail activity for each state and across the region, observational bias in the reporting of hailstone size, and temporal trends in the number of hail reports across the region and in each state. This paper then explores a possible link between the solar cycle and regional hail activity. Daily observations of solar radio flux (at 10.7 cm) and National Weather Service hail reports dating from 1956-2006 were compared. A chi-squared goodness of fit analyses showed possible associations exhibiting weaker significance in Solar Cycles (S.C.) 21 and 22, and higher significance during S.C. 23. The recent appearance of a significant linkage may be due to changes in reporting effort, weather patterns, or both. Further study is required to distinguish observational artifacts from geophysical effects. Because hail activity is common to the Northern Great Plains, a deeper understanding of the effects of the solar cycle on hail and also the spatial and temporal patterns associated with regional hail may prove beneficial for climate prediction, weather forecasting, and underwriting of crop-hail insurance