A fast-moving windstorm wreaked havoc across the heavily populated corridor of Canada in Ontario and Quebec. The line of violent wind, rain, and thunderstorms lasted for hours. The storm killed several people, flattened crops and forests, damaged buildings and vehicles, and caused power outages to over one million people. A derecho can spawn tornadoes, but the wind damage is most commonly hurricane-force winds blowing in only one direction. The storms are not unheard of in Canada. But what is new is that this storm occurred in May and not the summer. The storm impacted 41% of the total Canadian population.
The Washington Post’s Capital Weather Gang writes:
Derechos often strike along the northern periphery of heat domes, where conditions are ripe for powerful thunderstorms. Indeed, very unusual early-season heat swelled over eastern North America on Saturday, with numerous cities in the eastern United States setting records.
The combination of this heat with moisture pulled north from the Gulf of Mexico encouraged extreme atmospheric instability, or fuel for thunderstorms, in eastern Canada. The storms erupted as this hot, moist air was met by a strong cold front marching eastward. This was the same cold front that caused temperatures in Denver to plunge by more than 50 degrees in 24 hours and helped spawned the deadly tornado in Gaylord, Mich.
Historically, far southeast Canada sees approximately one derecho event every four years, according to the Storm Prediction Center. But Saturday’s event was unusually far northeast and hit at an uncommon time of year; many Canadian derechos have struck in July or August.
The unusual characteristics of Saturday’s derecho may have been representative of a climate change-related trend in the location of such damaging thunderstorm events. According to the Storm Prediction Center website, “The corridors of maximum derecho frequency likely would shift poleward with time” as warm domes of high pressure expand north under global warming.
The Globe and Mail described the damage:
A deadly storm that swept across Southern Ontario and Quebec on the weekend, resulting in the deaths of at least nine people, has caused massive damage to large swaths of the electrical grid, which could leave hundreds of thousands of customers without power for days.
Ontario utility Hydro One said the storm, which started around noon on Saturday with winds reaching more than 130 kilometres an hour, toppled large electrical transmission towers in the Ottawa area, and more than 600 hydro poles across the province.
“The distinction with this storm is the severity of damage we’re seeing,” said Hydro One spokeswoman Tiziana Baccega Rosa.
“Steel transmission structures aren’t supposed to come down … it’s very very extreme damage.”
Wiki:
A derecho (/dəˈreɪtʃoʊ/, from Spanish: derecho [deˈɾetʃo], "straight" as in direction) is a widespread, long-lived, straight-line wind storm that is associated with a fast-moving group of severe thunderstorms known as a mesoscale convective system.[1]
Derechos can cause hurricanic or tornadic-force winds, actual tornadoes, heavy rains, and flash floods. In many cases, convection-induced winds take on a bow echo (backward "C") form of squall line, often forming beneath an area of diverging upper tropospheric winds, and in a region of both rich low-level moisture and warm-air advection. Derechos move rapidly in the direction of movement of their associated storms, similar to an outflow boundary (gust front), except that the wind remains sustained for a greater period of time (often increasing in strength after onset), and may exceed hurricane-force. A derecho-producing convective system may remain active for many hours and, occasionally, over multiple days.
A warm-weather phenomenon, derechos occur mostly in summer, especially during June, July, and August in the Northern Hemisphere (or March, April, and May in the Southern Hemisphere), within areas of moderately strong instability and moderately strong vertical wind shear. However, derechos may occur at any time of the year, and can occur as frequently at night as during the day.
Where is the media?