Good day, I hope things are well with you and yours that you’ve been adjusting to the drop-off from our very warm first half of Autumn, into a more seasonable and even slightly-below seasonable second half of Autumn.

INTRODUCTION
Sometimes with New England weather (and possibly other regions of the world), there are old rules of thumb that border on lore that seem to come true more often than not. One of those has to do with the period of October and November during each Autumn season. When we see a cooler October and warmer November, we tend towards above-average winter temperatures across New England. Conversely, when we see a warmer October and a cooler November, the opposite tends to materialize.

If that remains true for this year, when combined with many other factors that would be in alignment with such a scenario, we could end up with above-average snowfall and below-average temperatures during the upcoming Winter of 2017-2018. Personally, based on what I’ve read and digested, and what my gut tells me, I think we will end up with above-average precipitation (including snowfall) and average, or slightly above average temperatures, given a pair of large-scale wild cards that are at play during the upcoming winter. However, these same wild cards that I will discuss within this report could lead to slightly below average temps and substantially above average snowfall. In other words this Winter looks like it will be slightly more “healthy” than last Winter, at the moment.

While some of my discussion may sound like techno-babble, try and stay with me. However, if you just want the two-minute summary, I have provided that below for you so you can “get in and get out” in a couple of minutes, and move on with your day.

Having provided that option for you, I don’t think I’m the only one that finds it fun to learn about the weather and its terminology. Most importantly, I hope to convey the potential for real-world human impacts on the surface of our beloved Connecticut River Valley and the surrounding hills, mountains, hollows and fields that we call home here in southwestern New England (i.e. a 50 mile radius with Northampton, MA at its center, which is generally my coverage area).

The Summary and Technical Discussion are both below for your perusal. Enjoy, and bring on the snow!

SUMMARY: WINTER 2017-2018
-A weaker than normal Arctic circulation is expected overall, allowing for periodic Arctic outbreaks into New England
-After a colder than average November, a warm-up is expected by end of the month into the first two weeks of December before another wave of colder than normal temps arrives for the second half of December into the first part of January
-A weak La Nina should promote an active northern jet stream, which will bring an ample number of Alberta Clipper systems into New England with light snows, as well as snow to ice/rain events. Some of these may amplify to produce moderate snowfalls.
-Periodic strengthening of the southeast U.S. ridge that is more typical of a more moderate La Nina will bring some inside runner storm tracks that will produce snow to rain, icing events, and some thawing periods.
-Speaking of which, a thaw of some degree is expected sometime in January to early February, after which a colder and stormier period is expected to recharge over New England with a few major snowstorms possible during February and March.
-Overall, slightly above average temps are expected.
-Overall, slightly above to moderately above precipitation is expected.
-Overall, above average snowfall is expected, similar to last year (2016-2017)
-This looks like a really good ski season for northern New England, so if you love the white gold and the slopes, this is a good year for you.
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TECHNICAL DISCUSSION: THE MAIN DRIVERS OF WINTER IMPACTS ARE LARGE-SCALE PATTERNS CALLED TELECONNECTIONS
When anyone attempts to discuss, forecast or report on a seasonal outlook, one has to examine a number of factors like analog years (i.e. years that the global pattern was similar to the current year), solar activity, and teleconnections. It is the snapshot in time of all of the global teleconnections that paint the atmospheric picture in the form of an “analog year” that helps us gauge what might transpire during the upcoming winter season.

Teleconnections are large-scale oceanic and atmospheric dipole patterns that oscillate between two extremes along a continuum. These patterns have varying time-scales, meaning that some like the PDO (Pacific Decadal Oscillation, an oceanic-based pattern over the northern Pacific Ocean) can remain roughly the same for 20-30 years before changing, while others like the MJO (Madden-Julian Oscillation, an atmospheric-based pattern over the western tropical Pacific Ocean) can change every month or so. This makes seasonal forecasts hard to nail down, and more similar to broad-brush strokes. While we can get a sense of some of the longer-scale patterns, the shorter-scale ones can change much more quickly.

There are many teleconnections at work that combine to form the northern hemispheric patterns through which the more regionalized and localized weather patterns at our planet’s surface play out, right over our heads and at eye level. I will refer to teleconnections such as the following in this report:

–AO (Arctic Oscillation): This refers to the permanent counterclockwise circulation of wind around the Arctic region.
–NAO (North Atlantic Oscillation): This refers to the atmospheric relationship of semi-permanent areas of high pressure and low pressure over the North Atlantic Ocean from Greenland to Scandinavia.
–EPO (Eastern Pacific Oscillation): This refers to the atmospheric relationship of semi-permanent areas of high pressure and low pressure over the North Pacific Ocean from Alaska to northeast of Japan.
–ENSO (El Nino/Southern Oscillation, which includes El Nino and La Nina): This refers to the oceanic relationship between warmer and colder surface waters of the tropical Pacific Ocean between Australia and South America.
–QBO (Quasi-Biennial Oscillation): This refers to westerly or easterly stratospheric winds above the tropics.
–MJO (Madden-Julian Oscillation): This refers to the eastward-migrating area of tropical convection activity, such as thunderstorms, from the equatorial Indian Ocean into the equatorial western Pacific Ocean.
–PDO (Pacific-Decadal Oscillation): This refers to the long-scale oceanic relationship between warm and cool sea surface water temperatures from the north-central Pacific Ocean to the west coast of North America, including Alaska, Canada, and the lower 48.

There are other teleconnections, but these are the main ones that help set the stage on which our local weather plays out from day to day, week to week, and month to month throughout our winter seasons. I will also discuss some other factors below, so with this very basic grounding in teleconnections, let’s jump into the details!

ENSO (La Nina), EPO, and QBO
More often than not, when you have an east-based weaker La Nina (the negative phase of ENSO) like we have setting up this late Autumn (i.e. colder than average ocean surface temperatures in the eastern tropical Pacific closer to the northwestern coast of South America), it allows for a large ridge of high pressure to form near the Aleutian Islands and Alaska. This negative ENSO state (the positive state of ENSO is El Nino, fyi) can also allow the Alaskan ridge to extend north into the North Pole. This tends to weaken the Arctic Oscillation (the counterclockwise circulation around the Arctic region that when strong, keeps cold air locked up there, and when weak, allows cold air to “spill” south in waves toward southern Canada and the United States).

In addition, ridges in Alaska and the Aleutians (given their clockwise flow) can promote the spilling of dislodged Arctic air masses southeastward into western Canada and the northern third of the United States. As previously mentioned, at times these ridges will extend poleward into the Arctic Region, and cause Arctic air to spread south and east into the Great lakes and New England regions as well. The Aleutian ridge is typical of the negative phase of the EPO.

As for the QBO, last year it was in its positive phase with westerly winds at the equator in the stratosphere. This year, we have a negative QBO with easterly winds, which fosters the development of ridging and warming in Alaska that also displaces colder air southeast through Canada and into the northern third of the country. This negative QBO phase is also associated with generating high-latitude blocking which forces such cold air southward into New England from Greenland. Likewise, this blocking suppresses the southeast U.S. ridge typical of a traditional La Nina-influenced winter. Such blocking, which refers to ridging that forms near Greenland, is also known as the negative phase of the NAO (North Atlantic Oscillation). Such scenarios are all in play this coming winter.

FUEL FOR COASTAL STORM DEVELOPMENT
Warm sea surface temperatures currently in the Atlantic Ocean south of New England will act as fuel to help in developing strong coastal storms when any east coast troughs are allowed to dig, amplify and combine with colder Arctic intrusions thanks to the aforementioned high latitude blocking events. This is part of why it appears we will get a blizzard or two, or at least a chance at several strong snowy Nor’easters.

SIMILAR GLOBAL PATTERNS FROM THE PAST: ANALOGS
I have read a number of meteorologists that I follow and respect very much (some who are old-school, long-time New England mets) continue to mention that this coming Winter shares common threads with the Winters of 1968-69, 1995-1996, and 2014-2015, and even 2013-2014 – all of which featured substantial amounts of snow and cold/arctic outbreaks, with a few mild/thaw periods.

SOLAR MINIMA AND MAXIMA
While solar maxima (periods when there is heightened solar activity impacting the Earth) tend to lock up cold in the lower and upper atmospheric vortices/circulations over the Arctic region, there are some correlations with lower solar activity and weaker stratospheric and tropospheric polar vorticies that allow that cold air to spill south into the U.S. One fairly uninformed thought is that with less solar adversity to handle, the polar vortices in the upper and lower atmosphere of our planet relax their normally tight circulations a bit more, allowing colder air to penetrate southward into southern Canada and the U.S.

When you combine this with a weak, east-based negative ENSO (i.e. La Nina state), which begets ridging (i.e. higher pressures) over Alaska that reach towards the North Pole, and a negative QBO (i.e. easterly winds in the tropical stratosphere), you tend to get more parcels of Arctic air exiting the high latitudes and spilling down into the United States. At the same time, the factors above tend to foster ridges (like the Alaskan/Aleutian ridge) to form over Greenland – also known as high-latitude blocking. As previously mentioned, a blocking pattern near Greenland can direct colder Arctic air down into New England once it exits the Arctic region. We had such Greenland blocking during the infamous winters of 1992-1993 and 1993-1994, both of which were very snowy for western Massachusetts. This will be a key to help determine how much snow and cold we see here in southwestern New England.

SIBERIAN SNOW COVER, CANADIAN SNOW PACK, AND WARM GREAT LAKES
In addition, Siberian snow cover is advancing across Asia, as is the Canadian snow pack. Both of these situations will provide colder air for cross-polar outbreaks when the Aleutian high builds north into Alaska, as well as help to cool the air that flows over Canada and into the U.S. Finally, the Great Lakes also have very warm surface waters this Autumn, and like the northwestern Atlantic sea surface temps, will provide plenty of fuel for lake effect snow events. This will certainly aid in snow totals over southern VT, the Taconics, Berkshires, western hilltowns and Litchfield hills, as those areas tend to become the eastern terminus for the strongest lake effect snow events.
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If you shop on Amazon.com during the year or for your holiday gift giving, you can further support me by visiting my store page where I’ve curated lots of quality weather-related products:
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THE WILD CARDS: PDO and MJO
The Pacific-Decadal Oscillation and Madden-Julian Oscillation are two teleconnections that could throw wrenches into our winter works, even when all the other large-scale patterns may align to produce an old-school, cold and snowy New England winter this year. Such a scenario is not likely, but possible.

The PDO is an oceanic oscillation that impacts the atmosphere, and the MJO is an atmospheric oscillation that impacts the shape of the jet stream that directs storm flow and tracking across the U.S., along with the positions of ridges that act similarly in directing cold air to different parts of our country.

PDO
With the base state of a weak La Nina, the PDO and its trends over the winter can have big, wildcard-like impacts on our winter weather here in New England. The PDO is currently in a negative phase, with cooler surface waters along the west coast of North America, and warmer waters in the northern-central Pacific. This is currently trending towards a more neutral or slightly-positive state. The bottom line is this: if the PDO stays negative this winter, it tends to strengthen La Nina, which would lead to more warm conditions over New England and less snowfall. This is because such a state strengthens the southeast U.S. ridge, allowing for storm tracks that pass to our northwest, which produce thaws and warmer periods during the winter.

However, if the PDO trends positively and reaches a more neutral state, La Nina will tend to, in kind, move towards a more neutral state, which would allow for more cold and snow in our region. This is one of the wild cards in this seasonal outlook report. The other is the MJO, or Madden-Julian Oscillation.

MJO
The MJO is another serious wild card when it comes to winter outlooks. Where the strongest tropical convection sets up between the area of east of Africa, through the Indian Ocean and into the western Pacific Ocean (northeast of Australia) helps to determine where and how the Pacific jet stream will buckle. We need tropical convection in western Pacific to help buckle the Pacific jet stream enough (i.e. make it run more south to north, a/k/a “meridional”) to cause troughs to amplify over the central and eastern U.S. to allow for the development of coastal storms that will track near New England. For winter lovers, this is one piece of the snowy puzzle which hopefully then coincides with cold air being directed by other teleconnections into New England to produce big coastal snowstorms.

IN CLOSING
Volatility and changes are expected this season, with a mix of cold and snowy periods, periods of icing events, and a thawing period sometime between the end of December and early February, with colder risks on the table to start and end the Winter. The potential is certainly there for an impactful winter. As I mentioned earlier in this report, I’ve heard more than one old-school, long-time meteorologist state that they are sensing a big winter coming.

Whether that happens or not, please follow me on my Facebook page by bookmarking it, and actively visiting it every day, especially during any stormy or dynamic weather events. I am there all through the winter, and every day of the year.

In other words, do not wait for me to show up in your newsfeed. While Facebook is making it harder and harder for me to show up in your newsfeed unless I pay hundreds of dollars per week to boost my posts, I am asking a favor of you by visiting my page directly. I plan on continuing to be there for you and yours every day of the week. Thank you for reading!

Sincerely, Dave Hayes (The Weather Nut)