Most significant storm of summer spawned 1 tornado in southern Ontario

Environment Canada has confirmed that Saturday's severe storm in southern Ontario spawned one tornado, spotted at 12:50 p.m., that affectedthe southeast shore of Lake SimcoefromSunset Beach to Port Bolster. The department also investigated reports of a tornado in the Oshawaarea, but concluded the damage there was "likely caused by a downburst."

The tornado has been ranked EF-1 on theEnhanced Fujita scale, which assesses storms based on wind speed. In the tornado area winds were estimated at 150 to 175 km/h.

ArnoldAshton, severe weather meteorologist with Environment Canadain Toronto, told CBC News that teams from the federal agencywould be inspecting damage on Sunset Beach on the southeast shore of Lake Simcoe, east of Barrie, andin the hamlet of Ashburn, north of Whitby, and the communityof Wellesley, west of Waterlooto determine the severity of the storm in each location.

"It was the most significant storm of the summer," Ashton told CBC News on Sunday. "It was downright tropical yesterday."

• Possible tornadoes touch down in southern Ontario
• Severe thunderstorm warning ends for much of southern Ontario

Environment Canada said the storms followed days of intense heat and humidity. Several clusters of severe thunderstorms dumpedheavy rain"more reminiscent of the tropics" in certain areas, whilesevere wind gusts caused sporadic damage to homes, structures, trees and vehicles.

There was a report of crop and tree damage in Ashburn at about 2 p.m. and there was a report of a tented structure being blown over with up to three people caught inside in Wellesley around 6 p.m. Ashton said a couple of people suffered minor injuries.

Downburst in Oshawa

In south Oshawa, however, Environment Canada has determined that damage to some homes, vehicles andtrees was likely due to a downburst, not a tornado, despite wind gusts of up to 120 kilometresper hour.

A damage survey team visited Oshawa on Saturday evening following reports by residents.

"We had one of our top guys go out last night to inspect while there was still light outside," he said. "it was an isolated area, about two, three streets of damage. We were led to believe it was a devastation zone. It turned out to be a few damaged homes and some damaged trees in south Oshawa."

He said the team determined it was two bursts of winds but the winds didn't leave what he called a "tornadic" signature.

"It has a certain look," he said.

Ashton said the damage survey teams look for telltale signs when confirming whether tornadoes have touched down. These include a long, narrow path of destruction and winds that appearon Doppler radar.

The federal agency estimates wind speeds in south Oshawa reached up to 120 kilometres per hour, which ranks as EF-0 on the Enhanced Fujita scale which is used to rate the intensity of tornadoes. It plans to do further analysis of the damage in coming days. Damage to homes and trees was reported at 2:25 p.m. in south Oshawa.

A downburst is a burst of very strong winds that come down from a storm, spread out and cause damage. The damage tends to be more spread out than in a tornado. A tornado involves rotation of winds, Ashton said.

"Things can swirl and look nasty in adownburst," he said. "It can almost looks like a cloud."

Significant levels of rainfall

Environment Canada said damage was also reported in Brampton around 1 p.m., withsome trees down, roof damage and shed damage.

Ashton said rainfall was significant due to the storms: Goderich received 78 mm, Ottawa 74.1 mm, Mount Forest 63.6 mm, Bancroft 59.7 mm, Uxbridge 56 mm, and Egbert 47.4 mm.

Durham Regional Police Service said in a tweet that no injuries were reported in Oshawa due to the storm and damage was mainlyreported in the Riston Road South and Outlet Drive area.