What is a 'derecho'? Climatologist explains Saturday's powerful storm
The storm that moved across Ontario and Quebec Saturday is known as a “derecho” (da-RAY-cho), a powerful kind of windstorm that is long lasting and far-reaching.
The derecho storm that slashed across southern Ontario and Quebec before moving into Maine left a path of destruction in its wake, and was responsible for at least eight deaths, including three in eastern Ontario.
Environment Canada Senior Climatologist David Phillips explains that a derecho is not a common term.
“It’s not a word we use very often because they don’t occur that often,” he told Newstalk 580 CFRA’s ‘CFRA Live with Andrew Pinsent’ on Sunday. “It’s sort of like a microburst or a thunderstorm but you get a whole army of those. Imagine soldiers lined up and just mowing down the front lines as they move along. Meteorologically, that’s essentially what happens.”
The storm moved into Canada from Michigan at around 11 a.m. Saturday, hitting London, Ont., Kitchener-Waterloo, Toronto, Kingston, and Ottawa, before moving up into Quebec and then to Maine.
“This storm was almost about 1,000 kilometres from Michigan to Maine as it went across Ontario and Quebec. That’s what a derecho is, it’s a long line of very active thunderstorms or microburst kind of situations. Nothing can deter it. It just marches along,” said Phillips.
Phillips said a derecho often has tornado-like or even hurricane-force winds. Ottawa saw wind gusts of up to 120 km/h and other locations saw even stronger winds.
But tornadoes, which are rotational storms, can still be embedded in the generally straight line of a derecho.
“There could be tornadoes embedded in that kind of derecho. I haven’t heard of a tornado report, but it doesn’t mean it can’t produce it,” he explained.
Western University’s Northern Tornadoes Project says it is investigating in the Uxbridge, Ont. area and just south of Ottawa, for evidence of possible tornadoes.
Just last week, the Northern Tornadoes Project confirmed an EF0 landspout tornado in the Casselman area, Ontario’s first tornado of the 2022 season.
Phillips says May can be a fickle month when it comes to the weather.
“You have that combination of warm, humid air that’s possible,” he said, noting the storm moved in when it was 30 degrees with a humidex of 38 on Saturday. “There is always that possibility of warm air in May, but the cold air in May is never too far away.”
It’s when cold, dry air hits warm, moist air that powerful storms can be produced, Phillips said.
“You can get air mass thunderstorms in July, but what you’re getting in May is that combination of the warm air duking it out with the cold air. In the springtime, this is why you can get some violent weather,” Phillips said.
“When you get that kind of one atmosphere changing to another, it’s usually heralded by some wild weather, and there it was.”
CTVNews.ca Top Stories
BREAKING | Person of interest identified in Chicago-area July 4 parade shooting that left 6 dead
Highland Park Police Chief Lou Jogmen said Monday afternoon that police have identified 22-year-old Robert E. Crimo III as a person of interest and cautioned he should be considered armed and dangerous.

Former Sask. premier Brad Wall gave strategic advice to key convoy organizer
Former Saskatchewan premier Brad Wall was in contact with a key organizer of the Freedom Convoy anti-mandate protest, providing strategic advice before and after the Ottawa occupation began, according to court records obtained by CTV News.
Daughter of Toronto Blue Jays coach killed in 'terrible accident' while tubing in U.S.
The 17-year-old daughter of the Toronto Blue Jays' first base coach died in a 'terrible accident' while tubing in the U.S. this weekend.
U.S. man to be charged with kidnapping, rape after Edmonton teen found: Oregon police
A 41-year-old man will be charged with kidnapping and rape after an Edmonton girl who was missing for more than a week was found, Oregon City Police said.
'It's the real deal': Doctors warn about future wave fuelled by Omicron variants
COVID-19 cases are rising again in Canada, with the two fast-spreading Omicron sub-variants known as BA.4 and BA.5 to blame. CTVNews.ca has a guide to what you need to know about the new variants.
Canada signs $20B compensation agreement on First Nations child welfare
The federal government says it has signed a $20-billion final settlement agreement to compensate First Nations children and families harmed by chronic underfunding of child welfare.
Canada Soccer makes new compensation offer to its national teams
Canada Soccer says it has made a new compensation offer to its men's and women's national teams.
Canadian airlines, airports top global list of delays over the weekend
Canadian airlines and airports claimed top spots in flight delays over the July long weekend, notching more than nearly any other around the world.
U.S. Capitol riot: More people turn up with evidence against Donald Trump
More witnesses are coming forward with new details on the Jan. 6 U.S. Capitol riot following former White House aide Cassidy Hutchinson's devastating testimony last week against former U.S. President Donald Trump, says a member of a U.S. House committee investigating the insurrection.