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1st tornado this year confirmed in the Heart of Illinois

The National Weather Service confirmed an EF-0 tornado in Mason County last night.

This tornado touched down 3 miles northwest of Mason City at 10:28 PM near the intersection of County Roads 1250N and 3300 N. It was on the ground for 6 minutes before it dissipated 4 miles north of Mason City near the intersection of County Roads 3400N and 1400N.

Peak Winds: 80 mph
Max Width: 30 yards
Length: 2.1 miles

The rotation can be seen using the velocity mode of our Live Doppler Radar. In this image, green means air moving toward the radar site, which is in Lincoln, and red is air moving away.

The small but tight red/green couplet north of Mason City is where the tornado was.

Another product that confirmed the tornado was our Debris Detector, which uses something called Correlation Coefficient. This measures how similar or different what the radar beam detects is.

For example, something similar like all rain or all snow would have a high value. A mix of precipitation types like rain and hail or rain and sleet would have a lower value.

This concept can be used in detecting tornado debris.

In the image below, you see an area of yellow north of Mason City. This is an area of lower CC, meaning that there was some debris present.

The National Weather Service says that while a few power lines were damaged, the debris captured on the radar image above was likely from a cornfield.

Brian Walder

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