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It’s Dueling Dual Jet Streams That Are Causing All This Weird Weather

How ‘bout that weather we’ve been having? The northern hemisphere has had some very strange atmospheric occurrences in the past month. As Popular Mechanics’ John Galvin reports, parts of Alaska had temperatures of 94 degrees on June 17, four degrees warmer than the temperature in Miami. Around the same time, parts of Canada and Europe were struggling with extreme flooding, forcing evacuations and devastating entire cities.

Dual Jet Streams Image Credit: NOAA ESRL PSD

How ’bout that weather we’ve been having? The northern hemisphere has had some very strange atmospheric occurrences in the past month.

As Popular Mechanics’ John Galvin reports, parts of Alaska had temperatures of 94 degrees on June 17. That’s basically the same temperature it was in Miami that day. Around the same time, parts of Canada and Europe were struggling with extreme flooding, forcing evacuations and devastating entire cities.

The flooding in Europe has already caused an estimated $3.93 billion to $7.59 billion in damage, and is still going on.  In Canada, experts anticipate that because of the damage, the country’s GDP growth will take a hit.

Even Alaska’s warm temperatures have consequences, with localized flooding and fire warnings going into effect.

Galvin spoke to John Nielsen-Gammon, a professor of atmospheric science at Texas A&M University, who explained that all of these strange and damaging weather events had the same root cause, a rare instance of two jet streams appearing in the northern hemisphere in the summertime. A jet stream, according to NOAA, is “a narrow band of strong wind in the upper atmosphere.”

Usually, there is only one jet stream during the warmer months—the dual jet streams only show up during the summer about once every decade. Currently, there is a small jet stream circling the Arctic, and another, larger one cutting across North America and Europe.

From Popular Mechanics:

With a typical jet stream, you see colder temperatures north of them, and warmer temperatures south of them. With two streams, the same effect is appearing, but in weird ways. McGrath is located just south of the curious Arctic jet stream—explaining those high temps—and Calgary is located just north of the central jet stream.

The floods in Calgary come from all the moisture that’s being channeled up from the Gulf of Mexico,” Nielsen-Gammon says. “In Europe the flooding is being fed from moisture being pulled out of the Mediterranean. It’s the same phenomenon.” The two jet streams have formed weather barriers that are locking rain and heat in place.

More from Smithsonian.com:

Thailand’s Flooding, As Seen From Space
Visualizing a Year of Extreme Weather
Can We Do Something About This Weather?

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