Persistent
Alaska warmth this fall has brought back ‘the blob.’ If it lasts,
it could mean a wild winter in the Lower 48
19 October, 2018
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.”
Over the next week, weather modeling indicates high pressure will move east into Canada as low pressure moves into the region where the blob is hanging out. (Tropical Tidbits)
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.
Okay
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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