Possible tornado touchdown in central Ontario

Scott Sutherland
April 19, 2013

A barn roof was torn off and thrown over 150 metres, with fallen trees and downed power-lines northwest of Shelburne, Ontario. Another barn is stripped of one of its walls and more downed trees west of Shelburne. Downed power lines in Riverview, Ontario, and around 20 hydro poles knocked down northeast of Newmarket.

These are the reports that came in as a line of powerful thunderstorms rolled through southwestern Ontario yesterday afternoon and evening, and Environment Canada has confirmed that the damage caused northwest of Shelburne was due to an EF-1 tornado, with wind speeds between 135 and 175 km/h.

The tornado touched down at around 5:45 p.m. EDT, roughly 6 kms northwest of Shelburne, causing damage along a track about half a kilometre long and about 75 meters wide.

[ Related: Possible tornado causes damage in Shelburne, Ont. ]

The Environment Canada weather forensics team investigating the damage has said that they will continue to look into this, and into the other damage sustained, and they can't rule out the possibility of other tornadoes yet.

Tornadoes aren't the only types of weather that can cause this kind of damage.

Thunderstorms can produce some incredibly strong winds, but the conditions aren't always right to get those winds rotating into a tornado. Sometimes, these storms can produce a 'downburst', which is a powerful blast of wind caused when hail or rain falls through dry air. The dry air causes the hail to melt and the raindrops (and melted hail) to evaporate, which draws a lot of heat from the air. Since the density of this cooled air is higher than the warmer air around it, it sinks rapidly. If this happens on a large scale, the downburst hits the ground and spreads out in all directions, creating strong gusts of wind. If you are standing nearby, all the winds from this downburst will be blowing in the same direction at your location, rather than rotating, but the winds can be just as strong as a tornado. If this happens on a small scale, it's called a 'microburst'.

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Now that this tornado is confirmed, it is the first tornado of the season for all of Canada, and the earliest tornado ever reported in Ontario. Previous April tornadoes happened in Ontario in 2009, when EF0 tornadoes caused damage to buildings in Windsor, Ottawa, and Gatineau on April 25th, and in 2011, when an EF0 tornado touched down near Fergus, Ontario, on April 27th, knocking down trees and ripping the siding off buildings.

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