Bloomberg Green has a story about heat domes, like the one that roasted us last week, and how their behavior is confounding weather forecasters. (The whole story is behind a paywall but you can read most of it if you subscribe to their Green Daily newsletter.)
Meteorologists know, for example, the jet stream — a river of fast-flowing air girdling the globe — naturally migrates northward in summer and they can measure how fast it moves. That metric is known as the Global Atmospheric Angular Momentum, and it’s among the best predictors for heat domes, said Matt Rogers, president of the Commodity Weather Group. When the value is low, as it is two weeks ago, “it can be a leading indicator of widespread, middle latitude heat ridges,’’ he said.
Climate change has warmed the planet, particularly the high latitudes. That influences heat domes in two ways. The first is their northward migration. That phenomenon played out in 2023 as a large ridge of high pressure parked across western-to-central Canada and kicked off a record wildfire season.
The second is changes to the jet stream. The temperature gradient between the poles and the tropics helps keep the jet stream taut, allowing it to push weather patterns along after a few days, Zobel said. But as the Arctic warms faster than the rest of the planet, that gradient weakens and is akin to loosening the grip on a rope. The resulting slack can cause the jet stream to kink, bend and buckle. The river of air can also sometimes split, creating a “kind of a no-man’s land” that holds heat domes in place, Cohen said.
Still, Arctic warming’s exact impact on the jet stream is an area of active research, Simpson said. Some papers haven’t been able to show the impacts that adherents of the weakening theory suggest, and others have come up with opposite results.
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