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BOSTON (CBS) – The flakes are starting to fly and the air is cold. Winter is not coming, it's here! Our annual winter WBZ-TV winter weather forecast as we make an attempt to figure out what the next season will bring. As always, there are some disclaimers which we'll get out of the way right off the bat.
1) Seasonal forecasting is still a science budding. It's not going to be slam dunk or something to take 100-percent literally. It's an educated guess using the science of all known variables involved. We've done some pretty good job in the past several years but it will be some parts that do not verify.
2) Climatological winter is December, January, and February. When we talk about a warmer or colder than average "winter," it's the average temperature over these three months. However, when it comes to seasonal snowfall, we take the entire October-April snowfall into account (and sometimes into May!).
3) Use the outlook as a guide for what lies ahead. We start getting requests for our winter outlook as early as September. It's an interesting project to look at everything we've got underway and prognosticate way farther out than our usual 7-day forecast. Every winter is dark, cold, and features snow. This is just an attempt to figure out how cold and snowy it will be. If you're not into the science, just skip to the bottom 🙂
Let's go!
What makes an extra snowy or quiet winter?
Snowfall over the past 30 years in Boston (at Logan Airport)
Over the past 30 years in Boston. There are some very big years and some very quiet years, giving us an average of about 45 inches of snow overall. So why are our winters so variable?
500mb height anomalies during some of our biggest winters for snowfall
Jet stream level zonal wind anomalies during some of our biggest winters for snowfall
There are a myriad of factors in our atmosphere that dictate how to go, but you can see from these charts a generalization of what produces a big year versus a 'dud.' In our major snow seasons (70+ inches) It is a more active subtropical jet stream or split-flow that adds extra energy and moisture to the coastal storm equation. You will also find a lot of ridging in the western U.S. and Canada, which we call a + PNA (Pacific North American pattern). This leads to the fall of the Arctic in the eastern United States and increases our chances of snowfall. A winter colder is almost always a snowier winter.
500mb height anomalies during some of our quietest winters for snowfall 
Jet stream level zonal wind anomalies during some of our quietest winters for snowfall
The dud winters (less than 20 inches) feature a much stronger and less "wavy" jet stream, which is still stronger than the rest of the world. This in turn keeps you in the middle of the high latitudes and allows you to move to the mid-latitudes. Ridging is a common feature in the east and keeps track of us.
We've had as much as 110.6 inches of snow in Boston (the memorable 2014-15 winter) and as little as 9 inches in 1936-37 and 2011-12. Quite a spread!
Does Wet Fall Mean Anything?
The question we have been asking for is the most important issue in the world.
We're walking across the Boston area. Graphic: WBZ-TV
If you look at the wettest fall seasons on record at Blue Hill Observatory, you'll find that nearly all of the following winners are featured here. ). That being said, I do not think that's going to be indicative of this upcoming winter. The Nina gold conditions ENSO neutral conditions (and one strong El Nino). None of them has a setup like this coming winter, which is a weaker flavor of El Nino.
El Nino Conditions and Overall Setup of Ocean Temperatures
We've been watching El Nino in the Pacific over the past several months, which is a warming of the equatorial Pacific. El Nino is a couple years ago, in 2015-16. It was crazy warming up in the game (a February blizzard) that made Boston's seasonal snowfall respectable. What we have this time around is not similar.
Current SST anomalies as of mid-November
This flavor of El Nino will be a weak to moderate strength central-based El Nino. Instead of having the most unusually warm waters closer to the South American coast, they'll be camped out towards the central Pacific. On top of that, the north pacific is on fire. Lots of very warm water south Alaska and also off of Japan. At the same time, we see the waters off the coast of Australia
The warmer waters matter because they help fuel the tropical convection (storms) which in turn releases large amounts of heat into the atmosphere. And that heat release helps to shape the jet stream. This lot of setup tends to favor a lot of ridging across Alaska and the US / Canada western, which in turn sends a trough down the eastern US Plus, the warm waters off the East Coast can add some extra fuel to developing nor'easters when cold air clashes against the mild ocean.
El Nino winters (http://www.nina.com/index.php?p=blogs/viewstory/2010) ). That being said, this year may buck that trend. There are a lot of indications that the western ridge would become more durable El Nino year would.
The Polar Vortex
Oddly enough, this term in the air in science and textbooks burst into pop-culture in 2013 and has been a favorite headline every sense. What is it? The polar vortex is a very strong circulation in the atmosphere that strengthens in the winter and weakens during the summer. When it's strong, it does not escape frequently. When it's 'disturbed' or in a weakened state, it can wobble and stretch and help frigid air farther south and 'empty the freezer door.'
Source: NOAA
It's taking a few months in the future. I would not say it 's on the ropes but it' s enough to get rid of a typical El Nino December. The million dollar question is in its way to stop it. In my opinion, the strength of the polar vortex is a major player in our temperatures and other atmospheric factors. We'll have to see how it works in December for later-season impacts.
The Solar Minimum
The solar cycle is a roughly 11-year cycle of sunspot activity. Recent research has made some links to where we are in the cycle and the strength of the polar vortex. In general, it is believed that high sunspot activity and help produce a stronger polar vortex while low sunspot activity can produce a weaker one. Being at a minimum now, it is more likely to be disruption to the future. For what it's worth (coincidence or not) the stretch from 2008 to 2011 featured some great snow winters from the Mid-Atlantic to New England.
Source: https://www.swpc.noaa.gov/products/solar-cycle-progression
The AMO
How about some more acronyms! The AMO is the Atlantic Multi-Decadal Oscillation. As the name suggests. it's a pattern that tends to change up after more than two decades. This is an oscillation that tracks sea-surface temperatures in the North Atlantic. It just happens that our seasonal snowfall does a nice job of tracking along with the AMO. The warm (positive) phase includes many of our snowboard stretches in the Boston area, while the cold (negative) phase captures a lot of our quieter seasons. We're likely to downswing, but still in + AMO territory and can probably squeeze out a few more years of these busy times before a possible flip. Next decade, perhaps?
Eurasian Snow Cover
There have been studies by Judah Cohen that suggest a link between the Eurasia and winter snow / temperatures. A stronger and more expansive Siberian high pressure in winter, which has a downstream effect of disrupting the polar vortex and bringing colder temperatures to the eastern US This autumn, we saw a fairly middle of the snow pack Advance of the whole of the northern hemisphere (continued)
Source: Rutgers Snow Lab
Conclusions! What's Expected This Winter?
If you made it through all that, congratulations! You are a curious person and I love that about you. If not, I understand. You do not want the labor, just the baby. That's fine too.
Here's how we see the winter unfolding. We know it's already snowing out there, and it looks like there's some early-season snow on the table late November through December. Ski season will be made easy and will be difficult to get into the holiday spirit. December feasible ends up colder than average.
If a month 'relaxes' and a chance for warmer than average temperatures, my money would be on January.
Most of our weak El Nino winters and most of the world computer guidance all point to a rocking February to March as 'prime time' for the winter. In my mind, North Atlantic blocking is the biggest issue. It looks snowy in the eastern U.S. goal if the blocking is to help the shire the snow track farther to our south to the 2009-2010. Either way, it looks cool with solid snow chances on the table.
For snowfall, we are calling for 55-to-65 inches of snow at Logan Airport in Boston, with higher amounts away from the coast. It should be an above average season for snowfall and perhaps by a wide margin. This is pretty remarkable, because it verifies it would make 6 of the past 7 snowier winters than average in Boston! This is quite warming long-term, so it's quite an interesting development. Four of the five warmest winters on record in Boston are since 2001 with 3 of them this decade alone. We have not had a Top 20 coldest winter on record in the last 60 years.
Which brings us to temperature. Overall, we expect a colder than average winter this time around. I think this will be most noticeable in February, compared to full years of complete blowtorches!
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