LINCOLN — Check the weather app on your smartphone in the middle of a clear day, and you might be surprised to see weather conditions forming in part of McLean County.
That may not a sign of inclement weather. Rather, meteorologists say, it is a side effect of wind farms cropping up across Central Illinois.
The massive size of the turbines, sometimes taller than 400 feet, and the wind they generate can create interference on nearby Doppler radar, said Chris Miller, warning coordination meteorologist for the National Weather Service in Lincoln.
That means the radar will display something that may look like rain or a storm in an area if it hits on a wind farm that radar can pick up anywhere from 20 miles to nearly 100 miles away, depending on atmospheric conditions.
“So it makes it look like a rain shower or a storm or something that might be there, but like on (a day) where we don’t have a cloud in the sky, something will show up,” Miller said. “And that’s just because of the proximity of those turbines.”
There are at least four projects the weather service in Lincoln picks up on its radar around Logan, Macon and McLean counties, Miller said.
In simplest terms, he said, radar works like this: It sends out a beam of energy that reflects off of objects, with the idea to measure anything that’s in the sky such as snowflakes or raindrops. Because of the size and reflective nature of the turbines, and the wind patterns found at wind farms, the radar gets a “false echo” of something in that area.
Meteorologists have overlays and other maps to know where the wind farms are so they know not to “trust the data” coming from that area, Miller said. But for radar sent out online, through popular weather smartphone apps or to local television stations, it’s up to the TV meteorologist or the viewer to understand the information.
“There’s no way for us to filter that out of there,” Miller said. “If someone is unfamiliar and they look at the data, there can be some confusion about why something is showing up that way.”
False signals have become more notable in a part of northern Macon County due to the completion just over one year ago of Radford’s Run Wind Farm, a 139-wind turbine project north of Warrensburg and west of Maroa that was the first to be built in Macon County.
Greg Elko, Director of Development and Senior Development Manager for Radford’s Run, said in a statement the project was reviewed by experts from National Oceanic and Atmospheric Administration and the National Weather Service prior to construction to ensure it would have a low impact on their radar operations and storm tracking ability.
"Our experts will continue working with the National Weather Service and other end users to capture any lessons learned and implement strategies for additional collaboration in weather forecasting and monitoring in the region going forward,” Elko said.
The issue came up recently as a major storm hit Central Illinois and moved through the west side of Macon County. The storm resulted in at least 23 reported tornadoes across Central and Southern Illinois, according to the National Weather Service, including an EF3 tornado that hit Taylorville and destroyed more than 100 homes. Some on social media noted the rotation of the storm seemed to stop on the radar while going over a wind farm before continuing again once it passed.
That’s an issue that comes with tracking a storm over a wind farm, said Kevin Lighty, meteorologist with WCIA in Champaign. Luckily, he said, most storms will not develop over a wind farm, meaning meteorologists and storm watchers can track the storm’s patterns ahead of time without any interference.
While false echoes from wind farms are a given, Lighty said meteorologists and other trained in storm-watching know what to look for, and it's not much of an issue when it comes to reporting on weather or presenting on television.
For those who use weather apps and come across an unusual weather pattern, Lighty said the best advice is to look at a “radar loop” or time lapse of the area.
“It’s pretty easy to pick out; (the wind farms) don’t move,” he said, adding that if the weather pattern doesn’t move on the loop, the viewer is likely looking at radar interference caused by something such as a wind farm.
Both Miller and Lighty said that taking in as much information as possible is also key to getting a full understanding of current weather conditions. That can include looking at other radars, such as the National Weather Service in the St. Louis and Chicago areas, which aren’t as accurate due to their distance but also will not pick up interference from the wind farms because they are measuring higher up in the atmosphere.
“If you’re not very adept at looking at radar data, you have to be very careful with what you’re looking at,” Miller said.