Sea surface temperature anomalies highlight the expansive blob of warm water around Alaska in October 2018. Graphic: earth.nullschool.net

By Ian Livingston
18 October 2018

(The Washington Post) – Throughout early fall, Alaska has been oddly warm and pleasant. The cause of the freakishly nice weather has been massive high pressure anchored over and around the state. One of the strongest on record for fall, this sprawling dome of warm air has helped keep the usual transition to cold stunted.

Since days are still long in early fall across Alaska, the sunny September (and into October) skies have also allowed ocean temperatures in the Northeast Pacific to rise significantly, as well. This has led to a return pool of abnormally warm ocean water in the Northeast Pacific known as “the blob," and just in time for Halloween!

But scientists are unsure whether the blob will remain a fixture or fade away. If it manages to linger into the winter, the consequences for the Lower 48 could be profound.

Although the blob is focused over the Northeast Pacific and the Gulf of Alaska, it has played a substantial role in the development of extreme weather patterns over the Lower 48 when it has formed in the past. Generally, it has been linked to abnormally warm and dry conditions in the West, and cold and stormy conditions in the East.

When the blob is in place, the jet stream, which both divides warm and cold air and acts as super highway for storms, tends to veer north over the top of the blob. This results in a big ridge of high pressure forming over western North America, which brings mild weather and blocks storms.

The blob’s presence was linked to the persistence and intensity of the drought in California from 2013 to 2015. It also ″was blamed for contributing to 2015 being the hottest year on record in Seattle,” according to Scott Sistek, a meteorologist with KOMO in Seattle. […]

After Alaska’s stunningly sunny September, warmer-than-normal conditions have persisted into October, despite some change in the pattern, which is now delivering more in the way of clouds and precipitation. […]

“The onset of autumn in Alaska — the wettest part of the year for south-central and southeast Alaska — has been slow to arrive by four weeks or so,” said Dave Snider of the National Weather Service forecast office in Anchorage.

Anchorage has yet to witness a freeze. Although the city could see its first freeze in about a week, that will be about 10 days to two weeks past the old record for latest, a substantial gap.

“Nome should have 20 freezes by now. This year just one," Brettschneider said. "Anchorage should have 20 days with temperatures below 38 degrees. This year, zero. So it’s not just the lack of a freeze, it’s that everything about the air mass is exceptional and persistent.”

Another oddity? Fairbanks has yet to see any snow so far this season, the latest on record. [more]

Persistent Alaska warmth this fall has brought back ‘the blob.’ If it lasts, it could mean a wild winter in the Lower 48.

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