Persistent
Alaska warmth this fall has brought back ‘the blob.’ If it lasts, it could mean
a wild winter in the Lower 48.
October 18 at 2:07 PM
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.
As the cold air displaced by the blob
has to go somewhere, it then often crashes south in the East. Remember the
polar vortex intrusions during the winters of 2013-2014 and 2014-2015? The blob
played a role.
So what will happen to the current
iteration of the blob?
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.
While
the National Weather Service Climate
Prediction Center is forecasting warmer-than-normal conditions
for Alaska the rest of the month, the mega-high-pressure zone feeding the blob
is expected to continue to shift and break down a bit. In its wake, a stormier
pattern may take over, at least for a time. This would allow the waters where
the blob currently resides to begin to mix better, perhaps ultimately
diminishing or even destroying it.
“How
long will BLOB Jr. last? At least as long as we have persistent high pressure
over the north Pacific," wrote Cliff Mass, a professor of atmospheric
science at the University of Washington, in a blog post.
At this point, "it looks like things are evolving to a pattern with less
high pressure offshore, so the BLOB should weaken.”
According
to Brian Brettschneider, a climatologist in Alaska, even if high pressure
persists, it may turn into a source of cold air rather than warmth given
Alaska’s waning sunlight — which would weaken the blob.
Ultimately, it’s hard to say much
conclusively about the blob’s fate.
The blob last showed up around this
time in 2016. Back then, there was some thinking that it may lead to a new
round of winter cold outbreaks in the East. That didn’t really happen, as the
blob dissipated.
Blob
or not, the damage has been done in Alaska, where drought persists
in the coastal rain forest of the southeast, and it’s been an
extraordinarily peculiar start to the cold season.
“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. But history shows that
the lack of snow so far means little with respect to what winter will bring
Much like the future of the blob, the
future of winter in Alaska is very much to be determined.
Brettschneider sees the potential for a
perfect confluence of conditions to keep the warmth coming. Since September
turned to October, a dominant feature has been a low pressure area in the
Bering Sea. This is a conduit for driving relatively mild Pacific Ocean air
into the state.
It’s still quite early in the cold
season, even in the snowy north. For now, it’s a waiting game. Waiting for
summer to finally end, and waiting to see what winter might bring. It won’t
only have implications for Alaska, but for all of us.
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