Record heat wave hits Alaska

Baked Alaska is taking on a new meaning this week. Temperatures in Anchorage, the country's northernmost city with a population of more than 250,000, reached the 80s and are expected to remain high through the weekend.

Meteorologists say the jet stream, a big river of air high above Earth that dictates much of the weather for the Northern Hemisphere, is causing the unseasonably high temperatures. The jet stream has been unusually erratic the past few years. They blame it for everything from snowstorms in May to the path of Superstorm Sandy.

The jet stream usually rushes rapidly from west to east in a mostly straight direction. But lately it's been wobbling and weaving like a drunken driver, wreaking havoc as it goes. The more the jet stream undulates north and south, the more changeable and extreme the weather.

"I've been doing meteorology for 30 years and the jet stream the last three years has done stuff I've never seen," said Jeff Masters, meteorology director at the private service Weather Underground. "The fact that the jet stream is unusual could be an indicator of something. I'm not saying we know what it is."

Right now, wind patterns in Alaska are carrying air in from the south and southeast. The state's all-time record high was set on Tuesday in Talkeetna, when temperatures spiked at 96 degrees. The small town's previous high was 91 degrees. In the town of McGrath, temperatures reached 94 degrees. Just a few weeks ago, McGrath residents had to bundle up as temperatures dipped to 15 degrees in May.

There is one plus-side to the heat. Fairbanks resident Victoria Smith, 25, says its keeping the usual clouds of mosquitoes at bay, at least during the day. Smith added that her office at the University of Alaska, Fairbanks, is like a sauna. "If it wasn't for the fan next to me," she said in an email, "I'd be a gonner."

Fellow Fairbanks resident Meredith Lanis is making the most of the warm temperatures while they last. "I'm reveling in the heat and enjoying every minute," she said.

Reuters reports that local residents are flocking to the lakes and community pools to escape the heat, and they aren't the only ones looking to cool off -- in Anchorage, a moose invaded a kiddie pool, and others have been spotted around lawn sprinklers. Owners of pet reptiles, meanwhile, have been bringing their lizards and iguanas outdoors to enjoy the rare heat. Normally, they cannot withstand the cool Alaska temperatures.

The high temperatures have allowed wildfires to rapidly spread across the state, because the brush is drier than usual. When struck by lightning, it quickly bursts into flames.

Experts have mixed opinions on what is causing such variation in the jet stream.

Rutgers University climate scientist Jennifer Francis is in the camp that thinks climate change is probably playing a role in this.

"It's been just a crazy fall and winter and spring all along, following a very abnormal sea ice condition in the Arctic," Francis said, noting that last year set a record low for summer sea ice in the Arctic. "It's possible what we're seeing in this unusual weather is all connected."

"Statistically big heat waves are becoming more frequent all over, " says Gavin Schmidt, deputy chief of the Goddard Institute for Space Studies at Columbia University. "Although the specific cause of any one occurrence is related to the vagaries at the atmospheric circulation, those variations are acting on a warmer baseline. And so, more records are going to be set."

"There are some viable hypotheses," Stanford University climate scientist Noah Diffenbaugh said. "We're going to need more evidence to fully test those hypotheses."

The jet stream, or more precisely the polar jet stream, is the one that affects the Northern Hemisphere. It dips down from Alaska, across the United States or Canada, then across the Atlantic and over Europe and "has everything to do with the weather we experience," Francis said.

It all starts with the difference between cold temperatures in the Arctic and warmer temperatures in the mid-latitudes, she explained. The bigger the temperature difference, the stronger the jet stream, the faster it moves and the straighter it flows. But as the northern polar regions warm two to three times faster than the rest of the world, augmented by unprecedented melting of Arctic sea ice and loss in snow cover, the temperature difference shrinks. Then the jet stream slows and undulates more.

The jet stream is about 14 percent slower in the fall now than in the 1990s, according to a recent study by Francis. And when it slows, it moves north-south instead of east-west, bringing more unusual weather, creating blocking patterns and cutoff lows that are associated with weird weather, the Rutgers scientist said.

Mike Halpert, the deputy director of NOAA's Climate Prediction Center, said that recently the jet stream seems to create weather patterns that get stuck, making dry spells into droughts and hot days into heat waves.

Last fall, a dip in the jet stream over the United States and northward bulge of high pressure combined to pull Superstorm Sandy almost due west into New Jersey, Francis said. That track is so rare and nearly unprecedented that computer models indicate it would happen only once every 714 years, according to a new study by NASA and Columbia University scientists.

"Everyone would agree that we are in a pattern" of extremes, NOAA research meteorologist Martin Hoerling said. "We don't know how long it will stay in this pattern."

In Anchorage, the average June temperature is 54.4 degrees Fahrenheit; the average high is 61.6 degrees. According to Weather.com, the hottest day on record was June 14, 1969, when temperatures reached 86 degrees. The last time temperatures reach the 80s was June 10, 1995. The current extreme highs are expected to last through the weekend.

Editor's note: This article was revised to reflect that Anchorage is technically the northernmost city in the U.S. based on population size.