Environment Canada has confirmed a tornado did touch down in Petrolia on Wednesday.
According to meteorologist Gerald Cheng, damage surveyed in the area near Sarnia, Ont. was consistent with an F1 tornado, which means wind speeds reached 140 kilometres per hour.
"The damage path of the tornado was roughly five kilometres long," said Cheng, adding that the damage was about 200 metres wide.
Cheng said the damage shown in photos of a barn, several sheds and downed trees would be easily caused by F1 wind speeds.
"Southwestern Ontarians are no strangers to the phenomenon," said Cheng about tornadoes in the region. "It's not out of the ordinary."
Environment Canada was assisted by a group that operates out of the University of Western Ontario in London.
David Sills is the executive director of the Northern Tornados Project (NTP), which aims to detect as many tornados across Canada as possible.
"We have the ambitious goal of getting them all if we can," said Sills. "In the last few years we've been able to find a lot of the tornados that are typically missed because we've got tools that let us into places that aren't really populated."
Deciding whether or not a tornado has touched down
The NTP uses satellite and aircraft imagery, as well as putting people in the field to survey damage whenever possible. Two NTP researchers visited Petrolia to determine if a tornado had touched down.
"It was a complicated event because it was a mix of tornado damage and what we call 'burst down' damage," said Sills, who was one of the researchers who went to Petrolia.
Sills said the debris pointed to a narrow, thin long line, which is what confirmed the storm system as a tornado.
In the field, NTP researchers are looking for a gradual buildup of damage, rather than going from "no damage to a lot of damage," said Sills.
NTP has been sending teams across Canada — as long as there's an airport or access roads nearby — to survey possible tornado damage on site. They also have meteorologists on the team to forecast for internal preparedness. All of NTP's data is posted publicly online for interested people to take a look at.
Both Sills and Environment Canada's Cheng said more storms and possible tornados may be ahead for southwestern Ontario this weekend.