The Yukon-Kuskokwim Delta isn’t known for its scorching summer temperatures, but a few days this July have been especially chilly.
Over the weekend, high temperatures recorded at the Bethel Airport on both Saturday and Sunday were in the 40s. That’s around 15 degrees below normal; the normal high temperature in Bethel at this time of year is 64 degrees Fahrenheit.
Alaska climate specialist Rick Thoman said that it’s the first time in 53 years that Bethel has had back-to-back July days with highs that didn’t top 50 degrees Fahrenheit.
“That is quite unusual, just to even have one day with highs in the 40s in Bethel in July,” Thoman said. “And we have to go back to 1971 to (find) the last time we had back-to-back days in July with high temperatures in the 40s. So (it’s) a very unusual event sparked by a very unusual outbreak of cold air from the high Arctic right into Southwest Alaska.”
Thoman said that it’s been a “really interesting” summer in the Bering Sea region, climate-wise. Two “cold pools” of air have developed and lingered around the Bering Sea – one in June and one in early July. He said that those cold pools of air have wobbled around Western Alaska for weeks at a time, bringing cloudy, cool weather.
“These pools of cold air, they are disconnected from the jet stream,” Thoman said. “And so they can be very long-lived as we’ve seen the last couple of months in our area. Why they form is basically, the atmosphere is a fluid and sometimes these little pools just spin up and because they are separated, or can be separated from the larger flow, they just spin around and seem to take on a life of their own.”
Thoman said that the cold pool of air that caused the depressed high temperatures over the weekend in Bethel “made a beeline” from close to the North Pole down to the Bering Sea around the Fourth of July, where it expanded.
“This package from Santa at the North Pole, lots of cold air (was) entrained in it, and it has been spinning around the Bering Sea since then, and over the weekend was centered just about over the Y-K Delta. And as a result, unseasonably cold temperatures along with some rain across the region,” Thoman said.
The cold pockets of air aren’t totally uncommon. They form and move around the atmosphere all year long, but in Alaska they’re most common in the springtime.
“In the summer, they tend to be confined to the high Arctic, say North Slope and northward,” Thoman said. “But that’s not been the case this summer.”
Thoman said that the strange weather isn’t necessarily part of a larger pattern or some major shift in the Yukon-Kuskokwim Delta’s summer norm.
“This particular little pool of cold air, it’s actually quite small in scale,” Thoman said. “So even though it’s been chilly in the Y-K Delta, you know, most of Alaska has been on the warm side, (and) of course, globally, it’s on the warm side. So it really is a case where all weather is local. We want to be take caution in extrapolating that too far beyond what we see out our door.”
In the coming days, Thoman said that the cold pool of air is forecast to move eastward over Interior Alaska. But toward the end of the week, high pressure from across the Bering Sea could bring drier, warmer air to the Y-K Delta – not record heat, but a big change from the cold and rain.
