The very strong El Nino of 2015-2016 ended in April of
2016. At this time it was thought that a La Nina would follow for the Fall into
the Winter. The ENSO neutral conditions
did turn to a very weak La Nina. But it quickly faded, leading to ENSO neutral
heading into the late Fall and Winter, then we quickly started the transition
to another El Nino. This is the first
time we've gone from a strong El Nino to a brief neutral/weak La Nina, Back to
a developing El Nino.
The problem was it takes the atmosphere awhile to
adjust from one state to another. All of this change in such a short time, made
things very complicated and unpredictable.
As the winter progressed we saw SSTs climb west of
South America in the Tropical Pacific.
The positive EPO kept the pattern transient; the lack of blocking kept
winter at bay.
Adding to this problem we had that warm pool of warmer
than average SST in the northern Pacific at the start. But, then the SSTs
quickly cooled from the Gulf of Alaska and along the coast west of Canada. This
had a big impact on the jet stream, keeping the colder air locked up in western
Canada, instead of moving into the eastern CONUS.
Another thing that lead to the warm winter of 2016
-2017 was the warmth in the Arctic. This allowed also helped keep much in the
way of cold air invading the eastern part of the CONUS, we just didn't have
much in the way of arctic air to work with.
The transience last winter made it impossible for cold
and wintery conditions to stay and get locked in. The fast jet stream and lack
of blocking were just too much. We got cold, saw snow, then it warmed and the
snow melted. Those areas, that had no snow cover stayed even warmer.
Here is a look at winter overall temperatures, along
with a look at overall temperatures for December, January, and February. They
show that the early cold in December, never returned for January and February,
leading to one of the warmest winters on record.
December
January
February
Winter overall
The main complaint I've seen directed at me, was the
lack of snow in the Northeast. But there
is where the problem starts. It might be hard to believe, but much of New York,
New England, into Pennsylvania saw above average snowfall last winter. The area that saw substantially below average
snowfall was the Mid Atlantic.
Here is a map showing how last winter turned out
snowfall wise. I've also included a chart that shows total snowfall for eastern
cities.
My temperature outlook for Winter 2016-2017 was a complete bust overall. But my snowfall outlook came in very close to what ended up falling.
The pattern that interfered with last winter, is the
same pattern that is causing all the issues with spring 2017.
Forecasting weather is difficult, even in the short
term. But to try and look out 4-6 months into the future is near impossible. A
seasonal outlook, paints with a broad brush and is a bit vague when it comes to
some of the details. The only tools I have are teleconnections, climatology,
and analogs. I try to fill in the blank spots the best I can. Most of the time
my seasonal outlooks are very good and end up close to the way things go down.
But like the winter of 2016-2017 outlook they don't all the time. Comparing my outlook for last winter to the
other outlooks from major outlets, mine ended up better than most. One other
thing, the Northeast is a very large area, so there will always be winners and losers
when it comes to overall conditions.
I've made a couple of post on why last winter went the way it did..... you can check them out.
I've made a couple of post on why last winter went the way it did..... you can check them out.
