Friday, October 18, 2013

My First Thoughts on the 2013-2014 Winter Season.

We have a ways to go before real winter. But things are getting ready to cool off.  So here is my first thoughts on the upcoming winter of 2013-2014. These are my first thoughts on our upcoming Winter. This is not a forecast; rather it is, for all intents and purposes an outlook based on my thoughts as of now

Will this winter be like the non winter of 2011-2012, more like 2009-2010, or something in-between.

If you've read my other winter outlooks. You know there are various atmospheric/oceanic signals used to try and figure what the coming winter will be like..



One of the major forecast factors is always the state of the  late fall/winter El Niño-Southern Oscillation (ENSO). I've gone into more detail on what the  ENSO  is in past winter outlooks, If you want a more detailed explanation you can read them. Last year's can be found Here. For the purpose of this post, .ENSO refers to the relative sea surface temperatures (SST) in the eastern tropical Pacific Ocean.

When temperatures are cooler-than-normal we have a La Nina, which is by and large means a warmer and drier winter in the Northeast. During La Nina the polar jet stays up  around Alaska and then drops down into the Northern part of the US. During La Nina Arctic and Siberian air will at times intrude into the Northeast.  

When temperatures are warmer-than-normal it is called an El Nino, which is normally wetter and cooler across the Northeast. Outbreaks of very cold Arctic air are much less common during an El Nino winter.

This year, the SST is running close to normal, so as for an ENSO signal for the upcoming winter, it's keeping its cards close to the chest. So the ENSO look to be neutral. As you can see in the chart below. A Neutral ENSO is 0.5 above down to -0.5 below the center line.


During ENSO neutral conditions, the jet still can bring colder air into the Northeast. However storms don't get as much help from the  southern subtropical jet. One thing I've noticed is there is a lot of Greenland blocking during an ENSO neutral winter. Moisture out of the Gulf tends to move to the SE coast where it can move up the coast.  In a neutral ENSO the southern jet stream plays a huge rule in ice/snow events in the Northeast, timing of cold air outbreaks and storms is critical. 

These ENSO phases peak during the winter and early spring, but weaken as summer approaches. So even if an El Nino developed in January or February it wouldn't make a difference for snow in the Northeast. 


Another important forecast factor is the North Atlantic Oscillation (NAO). The NAO is an index that measures the state of the's the difference in pressure (placement of low and high pressure) between Iceland and Greenland down to the Azores and over into Spain. The NAO is a very good indicator of cold air in the Northeast. The only problem is the NAO can only be forecasted out 2-3 weeks. Last year, I described how I forecast the NAO for the it is if you want to read about it and see how I do it.

Chart showing the two phases of the NAO.


The PDO is based upon patterns of variation in sea surface temperature of the North Pacific; it's highly correlated with sea surface temperature in the northern California Current.  As with the other teleconnections , it has two phases. warm (positive) and cool (negative).

The phases normally persist for decades. But that changed in 1998. The PDO entered a cold phase that lasted only four years. It entered a warm phase of three years, from 2002 to 2005. The PDO was in a relatively neutral phase through August 2007, but unexpectedly changed in September 2007 to a negative phase that lasted for almost two years, through July 2009, because of a moderate El Nino event that developed at the equator during the fall/winter of 2009-2010. This positive signal continued for 10 months (August 2009-May 2010) until June 2010, when persistently negative values of the PDO initiated and have remained strongly negative since then.   


Why all of these wild swings in the PDO over the last 15 years? No one is really sure.


The QBO:

The quasi-biennial oscillation (QBO is a quasi-periodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of close to 30 months.

The QBO affects the polar vortex which in-turn affects the troposphere. The polar Vortex is a region of air that is contained by a strong west to east jet stream that circles the polar region.

Here is a chart that shows how the polar vortex can effect the weather across the North America.

I won't waste anyone's time on going into the QBO; if you want to learn more about it here is a paper.

There are recent indications that the QBO will head toward neutral. Looking back at past years, when the QBO moved to around neutral a negative NAO formed more times than not.

There are other things that go into an winter outlook: Past seasons, Tropical Activity, Arctic Oscillation (AO), The PNA (Pacific North American), among other things. I might show these in the next final outlook; but I don't want to get over technical.

Analog Years:

I looked at several years. Some of which were:1959, 1960, 1961, 1962, 1963, 1966, 1967, 1968, 1969, 1978, 1979, 2001, 2003, and others.

But for now at least, I found the years that matched up the best were the winters of 1961-1962, 1967-1968, 1968,1969, and 1978-1979.

Why those years? They were back to back neutral ENSO events, they were years that had a slow start to the tropical season, and all featured cold PDO's. There are other factors but those are the major ones.

Arctic Ice and Canadian/ Siberian snowpack:

Despite the warm start to fall, plenty of cold air has been building up around the Arctic Circle, Siberia and Western Canada. Right now, the amount of total snow and ice across the Northern Hemisphere is up to around 6.5 million square kilometers. That is above average by a bit more than 1 million square kilometers.

With the snow and ice, it's not surprising that a we see a pattern change coming. As I've been saying on my Facebook weather page, guidance suggests colder air will infiltrate the Midwest and Northeast, starting this weekend.  This theory is starting to show itself all the snowfall we've seen in some places in the Midwest.  

The Bottom Line:

To sum all of this up. I strongly expect to see high latitude blocking over Greenland. The ENSO, QBO, and other things does support this idea.

Our winter last year was largely ENSO neutral. Many times the winter was influenced by circulations other then the ENSO, mainly the NAO. For the winter of 2013-2014 could hold a few(maybe more than a few)  similarities to last year.

The long range models are showing  the cold outbreak next week will most likely stick around into the first part of November. But they are hinting at a warm up starting around mid November. But between now and then we could see some kind of snow event.

The Eastern US will likely see quite a bit of variability this season. But, the winter seasons really cold air most likely will get off to a slow start, then really start to ramp up around  mid-January through the end of the season. With the coldest air over the Midwest.  I do expect to see moderately cold air across northern NYS, Western NYS, And Northern New England for part of December into January.

The milder pattern during December and January will lead to more mixed precipitation events, for Southern New England, and Southern NYS, Southeastern NYS, Eastern PA, and Southern New England. But don't worry, the pattern will cool off for the 2nd half of winter.

As for snowfall, The pattern I  expect will allow for more clippers than average. Because of this, the Midwest and Great Lakes look to see above average snowfall for the upcoming season.  An active storm track through the Great Lakes during December and into a part of January is looking likely.  So, the lake snow-belts off of Lakes Erie and Ontario could do quite well.  The snowfall in the Mid Atlantic states, Eastern NYS, and Southern New England could only be below to near average this season. But do the high variability of the storms and cold air outbreaks, timing will have a lot to say about that.

These are just my first thoughts and subject to change. I will post my official outlook for the Winter of 2013 - 2014 in November.


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