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Forecast predicts warm weather in Alaska through September

  • Author: Yereth Rosen
    | Arctic
  • Updated: May 31, 2016
  • Published June 19, 2015

Alaska's heat wave, which has already resulted in record-breaking May temperatures, is expected to continue all the way through the start of fall, says the latest three-month forecast from the National Weather Service's Climate Prediction Center.

For the entire state, chances are that weather from July through the end of September will be warmer than normal, according to the center's three-month temperature outlook. The strongest chances for warmer weather are in Southeast Alaska and along the Southcentral Alaska coastline, where the probability is 65 percent or greater, while chances for cooler-than-normal are only 12 percent, according to the forecast.

"It certainly tilts warm," said Rick Thoman, the National Weather Service's climate science and services manager in Alaska.

Several factors are combining to keep Alaska warm, said Thoman, who spoke about the forecast in a Friday webinar hosted by the Alaska Center for Climate Assessment and Policy at the University of Alaska Fairbanks.

One important factor, he said, is the current positive phase of the Pacific Decadal Oscillation, an oceanic cycle that periodically switches, and its associated warm sea surface temperatures in the Gulf of Alaska and the rest of the North Pacific.

There are also warm water temperatures in the Bering Sea, a phenomenon that is not linked to the positive PDO, Thoman said.

Another important factor is the diminished state of Arctic sea ice, which is particularly low around Alaska, he said. Melt in the Chukchi Sea off the state's northwest coast is dramatic and resembles conditions from June 2011, which was "the earliest melt-out of record that we know of," he said. "This year is right on target for that, if not earlier."

It appears that a moderate to strong El Nino event is forming in the Pacific region, but that is not likely to affect Alaska temperatures during the three-month period, Thoman said.

As for precipitation, the CPC three-month forecast does not detect any significant change for Alaska. There is about a one-third chance of a wetter-than-normal season, a one-third chance of a drier-than-normal season and a one-third chance of a precisely normal season for precipitation, according to the forecast.

The CPC forecast relies on an seven different major North American models -- each of which is an ensemble of predictions -- from NOAA and other organizations, including NASA and Environment Canada.

The forecast also takes into account observed trends, such as the steady autumn warming in Barrow, Thoman said.

"Every single October since 2002 in Barrow has been significantly above normal," he said.

Other factors are folded into the forecast, which is an amalgamated "man-machine product," Thoman said.

He cautions that the July-August-September forecast is expressed in probabilities, not certainties. Even if there is a high probability of warm weather, "That doesn't mean that there can't be a cold week or a wet week," he said. And there remains a chance, though it is calculated to be small, the weather will be cooler than normal, he said.

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