NWT fires: Changing jet stream wreaking havoc on weather

NWT fires: Changing jet stream wreaking havoc on weather
A “lazy, meandering” jet stream is thought to be responsible for extreme weather like droughts and flooding, and is due to a warming Arctic.Photo courtesy of NASA Goddard Space Flight Center.

The seemingly inescapable drought sucking moisture from forests in the Northwest Territories could be the product of a lazy, meandering jet stream, made “wobbly” by climate change.

Mike Flannigan, a professor of wildland fire at the University of Alberta and former weather forecaster for Environment Canada, said recent research suggests the band of fast-moving air that directs high and low pressure systems around the globe is being impacted by the rapidly warming Arctic.

“Climate change research is suggesting that it’s becoming more wobbly, or lazy and meandering, because of the temperature difference between the equator and the North Pole,” Flannigan said. “That difference drives the jetstream, and we’re warming faster at the high latitudes than at the equator, so it’s weakening and getting to be like a lazy river.”

Flannigan’s hunch comes from a recent study by the Potsdam Institute for Climate Impact Research, which found that excess heat in the Arctic is weakening certain atmospheric dynamics, like zonal winds and eddy kinetic energy.

What it means is that weather patterns aren’t being broken up by the usual storms and are, instead, getting “stuck.”

“When (the jet stream) meanders, it parks itself. Last summer, you had an upper ridge over the Northwest Territories almost all summer long, which usually means hot, dry weather,” Flannigan said. “We’ve seen this in the past – we’re familiar with upper ridges and fire activity – but usually it doesn’t last the whole summer like it did essentially last year.”

A fire tornado rips through the forest in Oregon in 2013 as part of a massive fire complex, similar in size to those in the NWT last summer. Intense fire behaviour is becoming more of a norm through climate change.

Photo: courtesy of Oregon Dept. of Forestry/Marvin Vetter

A fire tornado rips through the forest in Oregon in 2013 as part of a massive fire complex, similar in size to those in the NWT last summer. Intense fire behaviour is becoming more of a norm through climate change.

In Sweden, he said, a massive fire – the size of which hadn’t been seen in 40 years – persisted throughout the summer last year because of a large, unmoving upper ridge over the country that saw hot, sunny weather with no rain.

The same was true of the NWT and other parts of western Canada last summer, Flannigan said. It also meant that certain areas were stuck with rainy, low pressure systems.

“That’s the unusual part that they think is tied to this lazy jet stream phenomenon,” he said. “Some areas got flooding, but other areas got drought.”

More warming, more fires

Though Flannigan said he can’t predict this summer’s weather with any certainty, he said active fire seasons tend to come in “clumps” and all indications so far show this year’s in the NWT will be intense.

“We’ve never had this much fire activity this early, in my recollection,” he said. “This is unknown territory to have fires – intense fires – in May. Usually the fire season is July.”

As the world warms through climate change, Flannigan said fire seasons will get longer, bring more lightning and draw more moisture from vegetation, for which current levels of rain cannot compensate, creating drier fuels for fires to consume.

“All future projections suggest we’re going to get the warming, but precipitation is going to stay about the same, roughly,” Flannigan said.

Wacky weather, fire tornados

Not only are the fires burning deeper and larger than ever before, but the extreme combination of hot, dry, windy weather is causing fires to take on new characteristics that make them more dangerous for crews to extinguish, according to Flannigan.

“Drier fuels, prolonged drought means the potential for very high-intensity fires, which will have fire whirls, fire tornados, very active spread, spotting – where firebrands are carried aloft by the wind and dropped a kilometre or two in front of the fire and start a new fire,” Flannigan said.

“Sometimes they’re so intense, we get something called a pyroCb, which is a fire-generated thunderstorm,” he said, noting the NWT has already been exposed to these.

Last year, Yellowknifers were overcome with “apocalyptic” black clouds that poured soot-laden rain across the city.

Flannigan said such “wacky” weather could be the new norm.

“This is what the future may hold. I tell people that weather’s really wacky, but it’s going to be even wackier and crazier in the future,” Flannigan said.

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