24
Wednesday, January 11, 2017 The Nugget Newspaper, Sisters, Oregon
WINTER: Nobody
predicted the scope
of storms
Continued from page 1
5 when two inches of snow
fell overnight. Four days
later the snow depth mea-
sured six inches as modi-
fied arctic air from northern
British Columbia filtered
into the region. A reinforc-
ing shot of arctic air arrived
on December 13 just ahead of
a moist low-pressure system
that took dead aim on Central
Oregon.
By December 15 many
of the town’s citizens awoke
to approximately two feet of
snow.
Temperatures moderated
slightly during the final four
days of 2016, but beginning
on January 3, 2017, an addi-
tional 15 inches of snow fell
on Sisters over a two-day
period. This was followed
by the coldest temperatures
of the season so far when a
potent arctic air mass moved
in from north of the Yukon.
The official low temperature
in Sisters on the morning of
PHOTO BY JIM CORNELIUS
Yeah, not yet.
January 6 was -20 degrees
Fahrenheit. Some thermom-
eters measured well below
that.
At this point, a fair ques-
tion to ask is whether any of
this was foretold by weather
experts last fall. Let’s take a
look back to search for clues:
In October many meteo-
rologists and climatologists
were trying to figure out
what the El Niño Southern
Oscillation (ENSO) signal
was going to look like after
registering one of the stron-
gest El Niños in 65 years
during the previous winter.
Though El Niño was weaken-
ing, many scientists believed
that autumn would bask in
its afterglow. So the call was
for warmer-than-normal tem-
peratures for the three-month
period October through
December.
Early last fall the ENSO
was predicted to fade to
neutral through the win-
ter, but by late October and
early November the signal
was declining faster than
expected. As a result, a
revised forecast was issued
to expect a weak La Niña to
develop this winter.
Now let’s take a look at
what actually happened:
October came in only one
degree cooler than average,
while the rainfall was almost
an inch above normal. But
November was a scorcher and
dry as a bone. The tempera-
ture averaged five degrees
above normal and only 0.29
inches of precipitation was
recorded, making it the dri-
est November in more than
58 years. Maybe effects of
El Niño would hang around
awhile…
But December was a
game-changer. No one
should be surprised to learn
that the month was downright
cold, as temperatures aver-
aged nine degrees below nor-
mal. Precipitation registered
slightly above normal but
produced a lot of relatively
dry snow. For the period
October through December,
temperatures averaged five
degrees below normal. This
aspect of the forecast has to
be considered a bust.
And what of the ENSO
signal? The current Oceanic
Niño Index, which only looks
at sea-surface temperatures,
has a value of -0.8 putting it
the weak La Niña category.
The Multivariate ENSO
Index (MEI) combines ocean
temperature with five other
atmospheric measurements.
That number is -0.21, imply-
ing that the ENSO is in a
neutral state. Climate scien-
tists seem to have gotten this
one right.
What does all this mean
for us? The real answer
is nobody is sure. Neutral
ENSOs, and to some extent
PHOTO BY JIM CORNELIUS
Chillin’ in Sisters...
weak La Niñas, do tend to
introduce a bit more uncer-
tainty to seasonal forecast-
ing. But this signal of the
ENSO and the occurrence of
extreme weather events seem
to enjoy a higher degree of
correlation than do other val-
ues of ENSO.
Does this mean we
are likely to endure more
extreme weather this winter?
Again, nobody knows. So
buckle up, sit back and enjoy
the ride.
The outlook for January,
issued by the Climate
Prediction Center on
December 31, is calling for
temperatures to be much
below normal with precipita-
tion amounts slightly above
average.
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