Monday, November 13, 2017

An updated look at the pattern for the 2017-2018 winter outlook.

I've decided to make a update to the winter outlook I posted back on the 11th of October. If you've followed either of my two Facebook pages or on twitter, then you know, I've been saying for 5 mouths, I've been saying winter 2017-2018 was going to be cooler and have more winter precipitation than our last two winters, and this update will stay that course.

A little about my approach to long range forecasting:

Back when I was saying all of this, The Global Forecast System (GFS), European Computer Forecast Model (ECMWF), Canadian Model (CMC), Navy Global Environmental Model ( NAVGEM), and the Japan Meteorological Agency ( JMA), and their associated ensemble model products, were showing the exact opposite. But like all models, these dynamical models have their issues and bias.  Making a forecast especially a long range seasonal forecast, Involves a lot more than just looking at models.  Many of the tricks and tools I use aren't even taught at any met school anymore, I was blessed to have a few old school profs, along with people showing me things when I did field work, that enable me to know some of these older ways of doing things.  So I take these tricks and old time rules, and apply them to the modern way of doing meteorology.  I think the two make a nice blend. Model interpretation and knowing how to blend models based on their individual weaknesses, an ample understanding of teleconnection processes, pattern recognition, doing the math yourself (not relying on the computer to do the dynamic meteorology calculations for you) (I also use a lot of advanced statistics), A good understanding of the atmosphere,  and some understanding of climatology, are all essential to making accurate forecast .  If forecasting was as easy as looking at some computer models, you wouldn't need me. The only reason I say all of this is: far too many meteorologist, weather enthusiasts, and weather geeks rely on weather models to determine what the weather will do. IMO this is a poor forecasting strategy, that more often than not leads to failure.  I pride myself in giving you the best real analysis you will find anywhere.  There might be paid weather outlets that provide the same service, but I have yet to see a free site that provides a superior product than I do.  

Anyway on to the updated outlook:

No two winters are alike!



El Nino-Southern Oscillation (ENSO):


Like all teleconnections, the ENSO has a positive , neutral, and a negative phase.  The positive phase is called El Nino and the negative phase is called La Nina.  The neutral phase is called La Nada.  La Nada winters are very cold in the Great Lakes, Northeast, into the Middle Atlantic.

Last winter was one that featured above average snow for much of the Northeast. ; while parts of the Mid Atlantic along the I-95 saw much less than average snowfall.  At the same time last winter was one of above average temperatures, in spite of a cold March the winter was well above average in the temperature department.

Right now, we're in a weak La Nina. I've been saying for months that a weak La Nina was likely. La Nina winters tend to favor a very cold winter for the Upper Midwest and Northern Plains, While the Southeast tends to see very warm temperatures. The Middle Atlantic sees more in the way of average temperatures.  As is typical of La Nina, we've already seen a lot of high pressure in southeast Canada. Many times this setup can result in end of November and December ice storms in the Northeast. Last year was a weak La Nina as well. But this year there are a few key differences in the Pacific.  


Quasi-Biennial Oscillation (QBO):


For winter 2016-2017 we started heading for an East based QBO. But, that faded and we ended up with a west based QBO. This winter will have a QBO is that is east based. This will have a  big ramification on this winter season.  The state of the QBO has an subtle difference on La Nina.  When we have an west based QBO,  We have a trough near the Aleutians leading to a cold Alaska and western Canada; also there is a lack of high latitude blocking near Greenland during a west based QBO.  But with an east based QBO we normally see high latitude blocking. Along with a ridge out west. This warms up Alaska and displaces the cold south and east.  The cold rides the jet stream down into the East CONUS. Because of the High latitude blocking the southeast ridge sees more suppression than during a west based QBO.  

Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO):


Both of these teleconnections are kissing cousins .  When we have an east based QBO our winter season is much more prone to having a negative AO and negative NAO. This is the reason for all the high latitude high pressure over Greenland, leading to the upstream blocking.

Pacific  Decadal Oscillation(PDO):


The PDO is looking to be slightly negative to neutral for winter 2017-2018.  When the PDO is positive (warm phase) it can weaken a La Nina. When the PDO is negative (cool phase) it can strengthen a La Nina. 

The warm blob:

If you remember, back in 2013 a lot was beings said about the warm SST south of the Aleutian Islands. They dubbed this the "Warm Blob"  When this area of the Pacific is warm, the East Coast and Mid Atlantic have a much better chance of seeing a colder winter on average.

Warm SST in the Western Atlantic:

The warm SST's off the East Coast will help keep the Mid Atlantic and Southern New England a little warmer. But at the same time, if we do happen to see a Nor'easter form off the Southeast Coast, the warm water would vastly increase snowfall amounts for the big cities.


East Pacific Oscillation (EPO):


We're also having an negative  EPO.  When the EPO is negative this also implies a upper level ridge just off the West Coast and a trough in the east.  A positive EPO is the exact opposite. 

West Pacific Oscillation (WPO):

The WPO is strongly negative


And as I said in my winter outlook released in early October, years that have low solar activity, tend to be cooler during the winter.  Last year was also a low solar year, but the west based QBO worked against it.  For winter 2017-2018 that won't be the case.

An old weather observer who recorded weather events not only for his lifetime, but those of his Father and Grandfather as well, bequeathed his journals to me 12 years ago.  The journals are filled with all kinds of wisdom and observations, that have helped me immeasurably.  One thing they noted was that end of October and November  weather can be a good gauge as to what the winter will be.  If we have a cold October and warm November, on average we see more in the way of mild temperatures from December through March.  But when we have a warm October and a cold November, we often end up with the rest of winter being cooler and snowy.   

The Great Lakes are warm for this time of year.  That could very well play a role in early season lake effect snow events off of Lake Erie and Lake Ontario. In fact we could see a big lake effect event or two before Christmas.  

Looking at years like 1950, 1995,  2005, 2007,2008,2010, 2014 stack up well to what appears to be going on.

These winters seem to be a good match for what we can expect for this winter.

1950/1951,1960,1961,1968/1969, 1984/1985, 1995/1996, 1998/1999, 2005/2006 ,2009/2010, 2014/2015

Accumulated Cyclone Energy (ACE):

The ACE index deals with wind energy. It's used to try determine how active and distractive a particular tropical storm as well as entire hurricane season will be.  

Meteorologist  Joe Bastard and a few other meteorologist , are trying to correlate high ACE years with colder weather from November into March.  What I've seen of all this is interesting. Joe Bastardi of Wxbell, shows that because 2017 was a high ACE year, this coming winter will be cold. I don't know enough about using the ACE index to forecast cold winters. But like I said, the theory is interesting. 

What all of this means:


The next couple of weeks will be a fight between the cold building in the north and warmth in the south.  negative NAO and the positive EPO.  I do still think the EPO will turn negative. The WPO is just too negative for it not to.  


When you input the analog years into the models,  you end up with a similar look to what I show in my outlook.  Years that had two or more teleconnection similarities  November into March tended to end up cooler than average in the Northeast.  The idea of a blend between the current weak La Nina and a La Nada, also supports the idea that this coming winter will be cooler than many think.  When you put an EPO and the warm blob into the equation the trend is even colder. 

While La Nina winters tend to be overall mild for much of the Northeast. The Idea of an EPO and the warm blob will have a big influence on just how mild we will get.  So this winter will end up being a cooler La Nina.  As I've been saying quite frequently on my Facebook page, there is a lot of cold air building  across all of Canada. Because of the better chance for a negative NAO and negative AO, we could end up with a few polar vortex events. So even with a La Nina there is a chance for a few really cold arctic outbreaks.

 Winter will get an early start.  Most of the teleconnections are very strongly suggesting November and December will be cool.  So think most of us will see several chances for snow over the next few weeks heading into Christmas The global models especially the GEFS are having a lot of issues with the current pattern.  This all has to do with their individual biases and feedback issues dealing with the warmth in other areas of the planet. The cold in December should go into at least the first half of January. During January we could see a thaw that could last ten days or more. But the cold should come back into the pattern for February into March.  More or less a bookend winter.   

I expect Pennsylvania, New York State, and New England see the snowpack build. But La Nina winters are precarious, with swings in temperature. But overall I think we will do alright in the snow department.  La Nina winters favor a northern storm track into the Great Lakes and Northeast.  During La Nina we tend to see more clipper type storms then during none La Nina winters.  January to March tend to see quite a few snow chances  in the Upper Midwest and Northern Great Lakes, it also can get quite snowy across  Western Pennsylvania, much of New York State, Vermont, New Hampshire, and Maine. At the same time southern eastern Pennsylvania, New Jersey into the Northern Mid Atlantic  are a little less snowy.

With the active northern stream and the occasional surges north of the Southeast ridge,  winter 2017-2018 will see some ice storms, this will be especially true for the Mid Atlantic into Pennsylvania.  

Because of the active northern storm track, the Middle Atlantic won't see many coastal storms, all or most of their snow will come from clippers. The clippers will deposit snow in the Tennessee and Ohio Valley into New York State and parts of New England. So for Virginia, Delaware, Maryland, and southeast Pennsylvania the snow amount will mostly depend on clipper type storms. But we should still see a relaxing in the pattern from time to time, which would allow the southern stream to get involved in the pattern. So I can't rule out three or four Lows developing near the Gulf and then moving toward the Mid Atlantic and New England.  During a La Nina year the coastal typically form off the Delmarva or south of New England. When there is a strong to moderate La Nina, the Middle Atlantic sees warm temperatures and a lot less snow. However when we have a weak La Nina, snowfall seems to be closer to average.

But a Side note, often when we see a big storm in October, we tend to see at least one bigger storm during the winter.  Something to think about.  All it takes is one big storm to cause the Middle Atlantic to see above average snowfall.  The pattern is less supportive of this idea; but historically October storms can be a precursor to a stormy Mid Atlantic.    

For Pennsylvania west of I -81, much of New York State and New England will end up  overall with above average snowfall and below average temperatures.  most of eastern Pennsylvania east of I-81, temperature will be warmer than western Pennsylvania, but still below average overall.  Southeast Pennsylvania into the Mid Atlantic, will have a greater likelihood of seeing  some issues with the Southeast ridge; So there could end up to be average to slightly above average with overall temperatures for December into February.   I still think overall January will be the coldest month this winter. End of January into February we could see some temperature swings, as the cold pattern relaxes. Then for The rest of February and March we will once again end up below average with temperatures.

This winter will be colder than last winter here in the Northeast. Snowfall will be above average. 

The Middle Atlantic and the I-95 corridor will end up around average in temperatures  Snowfall  should be average to below average for snowfall.



As you can see there isn't a lot of difference between this outlook and my earlier outlook.
Remember a seasonal outlook isn't so much a forecast, as it is a broad brush to help guide us in what should happen.  I can't give you specifics as to what will happen or when things will occur. But generally this is what I think our winter of 2017-2018 will be like.