Driest July on record adds to drought, fire concerns

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This article was published 30/07/2021 (1245 days ago), so information in it may no longer be current.

Parched earth, persistent heat and piddling rainfall over the past four weeks has made for the driest July in Winnipeg in nearly 150 years.

While the team at Environment and Climate Change Canada was still finalizing the numbers on Saturday, meteorologist Justin Shelley said Winnipeg received just 8.5 millimetres of precipitation in the month of July, compared to the 30 year average of 79.5 millimetres.

“Based on the available data we have, it looks like it is going to be the driest July on record,” Shelley said in a phone interview with the Free Press on Saturday. “And that’s with 148 years of data.”

Throughout most regions in Manitoba, precipitation levels have been below average in the past month, leading to an extreme drought in the Pembina Valley area and making for tinder dry conditions with more than 150 wildfires currently burning in the province.

In the capital city, the 8.5 millimetres of precipitation recorded in July is the lowest since 2011 when the previous record of 9.6 millimetres was set. The third lowest precipitation level on record since 1873 was set in 2006.

Shelley said the remaining record low precipitation levels were set between 1875 and 1925. In July 2020 — another hot, dry season for Manitoba — Winnipeg received 39.2 millimetres of precipitation.

“I don’t know if there’s enough there to necessarily say there’s a trend, per se,” Shelley said. “But it does look like we are seeing some drier conditions within the last 20 to 25 years for the month of July.”

Shelley said the record low precipitation level in Winnipeg can be attributed to the heat dome that settled over the region in early July and climate change, which will continue to lead to more extreme weather.

“This year was pretty extraordinary across western Canada in terms of heat and drought,” Shelley said, adding it wasn’t just the heat dome that led to low precipitation levels.

“We’ve had multiple events in a row where we’ve had really hot conditions without a lot of precipitation, and it even looks like it’s going to continue into next week as well.”

Shelley explained that a heat dome creates a large upper ridge of pressure in the atmosphere which then produces hot, sinking air that eliminates much of the precipitation as it moves toward the ground.

“You need an unstable atmosphere so air is able to rise and condense and form precipitation, but with these weather patterns in place you actually have the opposite happening, which suppresses precipitation,” Shelley said.

“You can get systems and some precipitation along the edge of the ridge… but once you’re in the middle of it, it really just keeps things clear and dry, or I guess this year, smoky and dry.”

Shelley said current forecasts predict dry conditions to persist in Winnipeg through the first week of August, and while it’s difficult to say with certainty when the city may see significant or sustained rainfall, the outlook does not contain much in the way of relief.

“Southern Manitoba looks to be above normal temperatures and below normal precipitation for the month of August,” Shelley said.

The continued dry spell can also fuel itself as arid land diminishes the likelihood of storms developing.

“That can inhibit thunderstorm activity from occurring,” Shelley said. “When we have these extended periods of hot and dry conditions, you’re not adding any moisture to help aid in those thunderstorm developments in the future.”

Shelley said a rain system may move through the Winnipeg region mid-week but is unlikely to bring the widespread, prolonged moisture required to improve the precipitation deficit.

“It’s been a rough season so far in terms of drought and unfortunately it looks like that’s going to continue,” Shelley said.

 

danielle.dasilva@freepress.mb.ca