Southwestern Ontario’s eye on the sky for life-threatening weather could be obscured by giant wind turbines converging on its field of vision.
Recognizing and alerting people to severe conditions is a job where every minute counts.
That’s especially true in Southwestern Ontario, one of Canada’s thunderstorm capitals and part of Ontario’s tornado belt.
Hundreds of thousands of people in the region rely on Environment Canada to make the right call. But that task is about to get tougher.
The agency’s severe weather forecasters rely heavily on data from their Exeter Radar Station, about 50 km north of London, which detects storms and their velocity within a 250-km ring around the station.
The difficulty on the horizon are the scores of giant wind turbines being built or starting up within 50 km of the Exeter station. Some are planned as close as 16 km away.
The problem, documented by the U.S. National Weather Service and in Europe, is that when a weather radar signal is reflected back by spinning turbine blades, it can appear to be a rotating cloud or tornado.
Known as ‘wind turbine clutter,’ that can also disrupt precipitation estimates.
While software can filter out other interference, such as tall buildings and towers that don’t move, turbines can’t be because their giant blades rotate and constantly change direction with the wind.
“This kind of false information can be significantly misleading for forecasters under storm conditions,” Environment Canada says on its website.
The U.S. weather service has turned to university researchers to find a solution, but says on its website an answer is at least five years away, “assuming an acceptable solution can even be found.”
Asked what it’s doing to solve the problem for Southwestern Ontario’s radar, Environment Canada said it’s working with a number of wind farm proponents to better understand the potential impacts.
The agency “is supportive of renewable energy development. We are working actively with wind farm proponents on a case-by-case basis to explore ways they can co-exist without compromising our ability to provide quality weather forecasts and warnings,” Environment Canada wrote in an e-mailed response.
The federal agency also said it’s testing improved software to reduce wind-farm clutter.
Tom Jasper, who headed a disaster-relief committee in the days after a tornado struck Goderich in 2011, said he’d like to learn the details of what the U.S. National Weather Service has turned up.
“At this point, we’re certainly going to have a whole bunch more turbines up here,” he said.
“It’s an interesting hypothesis (that turbines interfere with weather radar). I’d be certainly always eager to hear more.”
A tornado packing winds up to 175 km/h, uprooted trees and downed power lines in the Grand Bend area last Sunday, after a tornado warning was issued.
Goderich Mayor Deb Shewfelt said he hasn’t noticed any difference in timing of weather warnings from before area turbines arrived, though those are outside the interference zone.
“They were broadcasting tornado warnings for pretty near 30 minutes ahead (of Sunday’s storm),” he said.
The most recent wind farms approved by the province within the Exeter radar station’s 50-km interference zone come with a stipulation an agreement be worked out between the developer and the weather agency for a so-called “exceptional weather event protocol.”
Environment Canada said it couldn’t provide details of the protocol to The Free Press, since they’re still being negotiated.
Wind energy giant NextEra Energy Canada, which has one wind farm operating in the Exeter interference zone and three more under development, said it’s in the final stages of negotiating a mitigation agreement that’ll give the agency the ability to request a change in operations of a nearby wind farm.
Part of the agreement will set up a communications system between NextEra and Environment Canada during extreme weather events.
“The course of action the operating team at the wind farm takes depends on the specific weather event, but one option is certainly to curtail, or shut the turbines down until the weather event passes,” said Josie Bird of NextEra.
— With files by Dan Brown, The Free Press
WEATHER RADAR AND TURBINE INTERFERENCE
— Weather radar uses an antenna to focus a radio frequency beam into the atmosphere
— When the energy strikes particles of precipitation, some of it is reflected back to the radar
— That information is used to help determine the type and intensity of precipitation
— Wind farms can reflect energy back to the radar system, contaminating the data and creating false precipitation and storm estimates
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