After a crop-damaging weather event, it may be of interest for people to learn just exactly what took place. While recent articles detailed the potential effects of the severe weather on growth and development of corn and soybean and discussed fungicides for hail-damaged crops, below is a weather summary.

During the early morning hours of Wednesday, June 22, the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service's radar returns triggered the issuance of several severe thunderstorm warnings for parts of Illinois: northern Warren and southern Mercer Counties.

Radars beam radio waves from an antenna and detect and measure reflectance, the energy of the wave that is bounced back toward the radar. The larger the object that a radio wave encounters, the more energy is reflected back. Doppler radars are able to measure the amount of moisture in the atmosphere and the distance and direction of movement of the storm from the radar's location. On Wednesday, Doppler radar detected heavy rain and the potential for strong winds and hail to fall in the area.

One of the figures above is a still capture of the radar reflectivity at the time of the maximum winds over the area. The redder and whiter that the area is shaded, the more intense the rainfall (and/or hail) is.

According to preliminary data collected at the Northwestern Illinois Ag. R&D Center in Monmouth by the Illinois State Water Survey's (ISWS) Water and Atmospheric Resources Monitoring (WARM) network, winds gusted to 78 mph. This was confirmed by an Illinois DOT Road Weather Information System (RWIS) station located on a hill on US 67 south of Monmouth that detected a 77 mph wind gust.

Meteorologists confirm that it was the rain-cooled air behind the leading edge of the storms that brought the straight-line winds that felled so much corn in the area (Figure). Hail also fell. According to NOAA Meteorologist Dr. Tim Gross, " In looking at the volume scans of the radar and other weather parameters that help estimate hail, I would say the size of the hail was between quarters and half dollar size hail (1.0-1.25" hail). As far as the area affected, most of it would have probably fell between Little York and Monmouth".

Preliminary WARM data shows that more than 3 inches of rain fell in Monmouth from midnight to 6 AM, with very heavy rain occurring at times (Figure).

References

Thank you to Tim Gross of the NOAA for supplying the radar images and analysis.

Jennie Atkins, Water and Atmospheric Resources Monitoring Program. Illinois Climate Network. (2016). Illinois State Water Survey, 2204 Griffith Drive, Champaign, IL 61820-7495