Monday, March 6, 2017

What the heck happened to Winter 2016-2017

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.   


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.

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