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The science — and art — of forecasting wildland fires

May 2020

On a beautiful spring day, it might be hard to imagine this is the calm before the storm. But wait. While Canada's wildland fire season is off to a relatively quiet start, it could all change as early as June according to seasonal forecasts from Natural Resources Canada's wildland fire research team.

In fact, early projections show that most of the country will be at 'above average' risk for most of the summer, while large areas of the country — from Yukon down through British Columbia and across the Prairie provinces — will be 'well above average' risk due to forecast high temperatures and average or below average rainfall.

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Atmospheric information gives Canada's wildland fire researchers a glimpse into the future. (credit: Lynn Johnston)

Not quite an exact science

Making seasonal predictions months in advance is a tiny part art and many, many parts science. No one knows this better than Richard Carr, NRCan wildfire researcher.

"Wildfire seasons are difficult to forecast because there are so many random variables," he says. "Yet wildfire managers — experts at the regional and local levels who respond to fires and try to manage resources — rely on forecasts to help make long-range decisions."

Technology has changed since Richard started at NRCan as a summer student 25 years ago. Back then, he was one of two trained meteorologists on site, so he was often called on to provide impromptu weather forecasts.

From ad hoc weather reports to an eight-person team

Those reports proved so valuable that the Canadian Interagency Forest Fire Centre asked for custom forecasts to help with their preparedness planning. Now Richard is part of an eight-person team that issues weekly, monthly and seasonal forecasts during Canada's fire season, which typically runs April through September.

The process begins as early as February, when the team starts looking at environmental factors. They measure the depth of snowpack, estimate when the snow might melt, monitor drought conditions and calculate how much precipitation fell over the winter. This information gives them a sense of what's happening at ground level.

CWFIS Update May
CWFIS Update Junee
CWFIS Update July
CWFIS Update Aug
 CWFIS Update Sept

A series of maps showing predictions for Canada's fire weather severity, summer 2020.

The powerful effects of El Niño and La Niña

They also look at what is happening far above the earth's surface and factor in climate and atmospheric conditions. For instance, is it an El Niño or La Niña period? Strong episodes of either phenomena can increase spring fire activity in Western Canada, while other ocean and atmosphere interactions may influence fire risk in other parts of the country. El Niño and La Niña events also usually affect the position and strength of the jet stream — the narrow strips of high winds that flow west to east across our country more than 10 kilometres above the earth's surface. These powerful winds can have a huge impact on climate by separating cooler air from warmer air and pushing air masses around.

Finally, the team folds in forecasts from two climate models developed and run by Environment and Climate Change Canada, which use data collected about the state of the atmosphere, sea surface temperature and sea ice. All of this atmospheric information gives Canada's wildland fire researchers a glimpse into the future.

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Wildland fires consume an average of 2.5 million hectares a year in Canada, equivalent to about half the area of Nova Scotia.

Measuring the human impact

Richard is careful to point out that NRCan's seasonal fire forecasts primarily help identify areas of increased risk — they don't reveal how many fires there will be in any one year or how devastating they might be.

How a fire season unfolds in reality depends largely on human behaviour. It's true that many wildland fires are caused by lightning strikes, but slightly over half of them are the result of human activities. And this year, there could be another factor at play: COVID-19. If physical distancing practices continue through summer — and campgrounds remain closed, large gatherings are restricted and campfires are banned — they could directly affect this fire season.

To put things in perspective, while it looks like things might really heat up this summer, the fact is every fire season carries risks.

"Fires still occur even in average seasons, and the potential for damaging fires always exists," says Richard. "There's technology and science to predict fire seasons, but we can't predict exactly how they're going to play out. No one can."

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