The Hail Storm: Why Here? Why Now?

By Tyler Williams, Extension Cropping Systems and Climate Resiliency Educator, & Al Dutcher, Associate State Climatologist

Hail Formation Graphic — Figure 1. Circulation pattern within supercell thunderstorms contributing to the creation of hail. (Source: Tyler Williams)

Record sized hail — Figure 2. A hailstone with a diameter of 7 inches and a circumference of 18.75 inches fell near Aurora, Nebraska, during a June 22, 2003 storm, setting the US record for largest hailstone. Since then, on July 23, 2010, a heavier hailstone (1.938 lb) with a larger diameter (8 inches) fell near Vivian, S.D., taking the US record.

Hail impacts many communities and industries each year, causing annual economic losses in excess of $1 billion. Hail can occur anywhere in the world; however, the topography and geography of the United States favor the development of tornadoes and strong hail-producing thunderstorms. Hail forms when warm updrafts in thunderstorms carry raindrops upward into extremely cold areas of the atmosphere (Figure 1). It is estimated that the updraft needs to be more than 80 mph for baseball size hail (2.75 inches) to develop.

The highest chances for hail on any given day in the U.S. are in late spring and early summer in the Great Plains. The higher elevation of the Great Plains allows the freezing level in the atmosphere to be closer to the ground, which helps hailstones grow larger than in other parts of the country (Figure 2).

Late Season Hail

Most hail events in Nebraska occur from May to July (Figure 3); however, in September 2015 late season hail was quite destructive. That month there were 80 hail reports in Nebraska, accounting for 18% of all hail reports in 2015. That is near the long-term average for July. The timing of a September hail storm is the most concerning issue. Soybeans that are at, or past maturity, shatter on impact from even relatively small hail stones and are a complete loss. Corn is a little more durable than soybeans at this point in the season, but large hail can break off ears and stalks, especially in mature crops that are brittle.

Hail Reports by Month Chart — Figure 3. Nebraska hail reports by month (percent of total) 1955-2015. (Source: Storm Prediction Center)

Severe Hail Days Per Year from 2003-2012 Reports — Figure 4. Number of severe hail days per year from 2003-2012, based on NOAA reports. (Source: National Oceanic and Atmospheric Administration)

Hail is never a good sight, but late-season hail after all of the hard work and money has been invested, can be devastating. If you face this challenge, see these tips for combining downed corn.