When I
posted my winter outlook last fall; I thought I was going to make a three
pointer at the buzzer and win the game.
For some areas my outlook went well, for other areas so far it's been
woefully wrong. While snowfall for Winter 2016 2017 isn't over yet. (Last fall
I said snowflake to snowflake), we can see a huge disparity between New York
State and New England compared to the
Mid Atlantic.
Places like
Syracuse, Boston, New York City, and Hartford saw above average snowfall (thru
the 5th of March). But places like Washington DC, Buffalo, Baltimore, and Atlantic City saw
well below average. Many places on the Tug Hill saw a well above average
snowfall...Redfield has seen over 300 inches.
So while New
York State and New England (especially northern areas) saw snowfall more or
less like my outlook showed. Those in Pennsylvania and the Mid Atlantic surely
didn't. The Mid Atlantic fell well below what I thought would happen.
As I've been
talking about the last few days on my Facebook Weather Pages. The 10 thru the
20th look to be cold with an active pattern. So there most likely will be more
snow, perhaps even in the Mid Atlantic States, how much is yet unclear.
As far as
overall temperatures for December to the 1st of March, that I didn't even come
close to being right.
Overall temperature anomaly from December 1st to March 1st.
This post
will touch on the important reasons winter 2016-2017 turned out like it did.
Why the
wacky winter?
When I made
my outlook, the teleconnection setup pointed toward ridging out west and
stronger troughing in the East. I had thought that we would see more blocking
near Greenland. The SST projections supported my thoughts back in Fall of 2016.
The QBO
(Quasi-biennial Oscillation)
When I
looked at the analog years, everything pointed toward a negative QBO on average
for the winter months. But it turned out that the QBO stayed strongly positive
for much of the time. I couldn't find anything in the historic record that
showed a weak La Nina, lower solar activity, with a positive QBO. Not saying
there haven't been, but I couldn't find one. At least until this winter.
The Polar
Vortex didn't weaken like the analogs showed it should. This was because the
+QBO allowed the westerlies to remain much stronger than average. The stronger
PV keep a lot of the cold locked up in northern Canada, with only a few weaker
surges of arctic air into the Northeast and Mid Atlantic.
The MJO
(Madden-Julian Oscillation)
The MJO is
one of if not the major cause of the way winter 2016-2017 went down. The MJO
has eight phases some of these associate cold in the East, others associate
warmth in the East. The MJO is difficult to use and forecast from, it only is
fairly reliable for around two weeks. Because of that it can't really be used
to make a seasonal outlook.
For winter
2016-2017 the MJO was very active. This effected Great Lakes, Northeast, and Mid Atlantic climatology. Weak to neutral La Nina's tend to be cold and
snowy in the Northeast. The MJO was so active that it overruled how a weak la
Nina typically impacts the Northeast and Mid Atlantic region. So we ended up with a warmer and less snowy
winter than was expected based on climatology.
Blocking:
What
blocking we did have largely stayed over eastern Canada instead of being
farther east closer to Greenland. This aided the troughing in southwest Canada
into the western CONUS.
The Pacific:
The ENSO (El
Nino- La Nina Southern Oscillation)
Last fall
everything in the Pacific looked to support my thoughts. We were heading into a
La Nina. But then as we got toward January things started to change, as there
seemed to be a transition to El Nino underway. The transition became very clear
by February as warmer than average SST (Sea Surface Temperature) returned to
the Pacific west of South America. This shift happened very quickly, much
quicker than I thought it would. These warm SSTs helped ensure that there would
be no locked pattern of cold in the Northeast.
The EPO
(Eastern Pacific Oscillation)
When winter 2016-2017
started the EPO was staying negative to neutral most of the time. This was one
of the main reason the first three quarters of December 2016 was so cold. Then
things changed, From around Christmas to the end of the month we blowtorched.
The last quarter of the month was so warm, that it wiped out all the cold
before it, making December above average overall in temperatures. The Cold came back for the start of January.
Then SOI spiked during the last week of December, so I knew a January thaw was
on the way. But the thaw went a lot longer than I thought it would. The reason
I thought it wouldn't last was the Sudden Stratospheric Warming event that
occurred at roughly the same time.
However, when combined with the timing of the MJO going into the warm
phases, made sure there just wasn't any cold for it to bring south into the
Northeast and Great Lakes.
The EPO
stayed positive for a large part of winter 2017, this assisted the ENSO to keep
the pattern transient, The Pacific and Northern Jet were allowed to stream too
fast. This helps keep the cold to the north, and greatly reduces storminess
along with making an unfavorable storm track for the Mid Atlantic into the
Northeast.
The PDO
(Pacific Decadal Oscillation)
We had
warmer that average SST in the north Pacific in the Gulf of Alaska and off the
Northwest Coast during late fall 2016. As we got into winter 2016-2017 those
warm SST cooled quite quickly. This allowed the Jet to keep the cold air
bottled up in Western Canada and the Western U.S. If the pool of warm SST had
remained, the trough would have come farther east, bringing cold into the Great
Lakes and East Coast.
Winter tried
to reverse things for the first 10-12 days of February, but the pattern being
so transitory ensured nothing could lock in. Se we warmed and torched once
again.
There are
other minor reasons for the way winter has turned out. But the ones I listed
above are the major ones.
