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Water Today Title October 20, 2018

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Update 2018/9/25
Extreme Weather


TORNADOS HIT OTTAWA-GATINEAU MANY STILL NOT REINTEGRATED INTO THEIR HOMES




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by Cori Marshall

Friday, September 21, 2018, multiple tornadoes touched down in eastern Ontario and western Québec, leaving debris and damage in their wake. The most frightening part is over, and the focus is on caring for those affected, clean-up and reconstruction.

A September 22 Gatineau update indicated that "the most heavily hit area has 215 buildings, including 1,686 dwellings." There was damage to "several buildings" trees were uprooted and the winds "damaged street lights." To deal with the situation the city mobilized "close to 200 municipal employees."

In Gatineau 212 building had to be evacuated and as of Monday, September 24, "1,379 people [had] registered at the victims' centre, including 437 families." In the aftermath of the extreme weather event, inspections were conducted and of the buildings that were evacuated "205 [had] been returned to the owners."

Yves Melanson, Public Relations Ville de Gatineau, said "at this point, it is premature to give an exact date for residents to reintegrate the severely damaged buildings," adding "owners will have to undertake structural analyses of the buildings."

We asked what, if any, impact the tornados had on the drinking water and Melanson said "the tornado did not impact the drinking water."

Ottawa was equally hit by the tornados. According to a September 21 City Announcement "the response was concentrated in two areas, Dunrobin [and] Hunt Club-Riverside."

The release noted that "approximately 25 residents were injured." It added that damage to some properties is severe, with reports of some houses collapsed and some roofs gone." The damage impacted approximately 100 buildings.

The events of last Friday were preceded by a "tornado watch", so we reached out to Environment and Climate Change Canada (EC) to find out what meteorologists were looking for to issue the warning.

Simon Legault, Meteorologist with EC, said that what they look for are the ingredients to create a thunderstorm, humidity and high temperature." Secondly, Legault said that "you need something to trigger the thunderstorms, normally we are looking for a cold front that can trigger a lot of thunderstorms."

Legault explained that in order "to create a tornado you need a wind shear, which is a difference in the speed or direction of winds at different altitudes." The difference in wind speed is what creates the rotation. When the rotation gets caught up "in the convection of the thunderstorm that is being created, it causes the twisting to extend into the air." Legault compared this to "figure skater [spinning] when they bring their arms into their bodies."

Legault underlined that "it is very difficult to forecast a tornado." If the right "ingredients" for a tornado are present EC issues a tornado "watch" and informs the public of the potential. It is when EC has satellite confirmation of rotation in a storm front "and are confident [they] will issue an alert like was done last Friday," Legault said.

EC updated the number of tornadoes today, and Legault confirmed that they "spotted six tornadoes," last Friday evening. "The strongest was Gatineau EF-3, another track south of Ottawa EF-2, farther west received a tornado of EF-1," Legault said. EC spotted another three in the upper Outaouais region.

The annual mean average for tornadoes in Ontario is 12, 6 for Québec.

There are categories attributed to tornadoes from EF-0 to EF-5. The range is called the Enhanced Fujita Scale (EF). Legault explained that "EF-1 would be winds from 135 km/h to 175 km/h, [...] and EF-3 would be from 220 km/h to 265 km/h." The tornado that hit Gatineau was an EF-3 though "it [winds were] about 225 km/h towards the lower end of the scale, when it was in the Dunrobin area of Ottawa it was stronger 250 to 260 km/h," Legault said. That is the difference in the damage seen on both sides of the provincial border.

Gatineau has been hit by many different weather events since early 2017, with major spring flooding, flash floods and now a tornado. Climate change has been put out in the media as a possible cause. Legault said that "climate change would help phenomena that need a long-term set-up to happen like flooding in the spring." Flash flooding and tornadoes "are short-term weather phenomena" and data has not been collected over a long enough period to make a determination.

Many people have returned to their homes, and the clean-up process has begun. There are still those who have not and need the help and solidarity of the community and donations can be made through the organization. The number of people who need assistance with accommodation continues to drop, there are still accommodation centres open to the public.

cori.marshall@watertoday.ca





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