SUMMARY FOR WINTER OUTLOOK OF 2016-2017
-The Winter of 2016-2017 will be unlike the Winter of 2015-2016 which featured the second strongest El Nino on record.
-We’ve transitioned from a super strong El Nino to a weak La Nina, with much cooler ocean waters in the equatorial eastern Pacific Ocean.
-This tends to foster a more northern U.S. storm track, along with cold temperatures in the northern U.S. down into the Midwest, which can seep into New England from time to time.
-It also fosters the intermittent emergence of a high pressure ridge off the southeast U.S. coast which provides milder thawing periods as well.
-Click this image to get more details.
-We’ve had heavy snowfall in much of Siberia in October, which led to the formation of cold high pressure in eastern Siberia. This high pressure will migrate towards Alaska at times.
-It’s the clockwise flow around the high pressure system that helped the Arctic air cross from Siberia, over the North Pole, and south down into western Canada and into the U.S. earlier this month.
-This looks to continue from time to time this Winter, giving us cold blasts and some moderating periods of warmer temperatures.
-The Polar Vortex, which is a permanent low pressure system high up in the Stratosphere over the North Pole has weakened, and is expected to variously strengthen and weaken again during this upcoming Winter.
-This weakening of Stratospheric circulation over the North Pole propagates down from the sky towards the surface, similarly weakening a permanent surface low pressure system called the Arctic Oscillation (AO).
-When the AO weakens, the circulation buckles, becomes wavy, and allows surface Arctic air to spill south into the U.S., which is expected to occur at times this Winter, which is completely unlike last Winter, when the AO was strong and locked the cold air in the Arctic.
-In addition, the North Atlantic Oscillation (NAO) is expected to transition into its negative phase at times this Winter.
-The NAO is an Atlantic Ocean atmospheric relationship of high pressure and low pressure. In its negative phase, high pressure exists over Greenland and low pressure over the Azores Islands.
-When this happens, as it did the big Winter of 1993-1994, it promotes the seepage of cold air from Atlantic Canada down into New England, as well as slowing storm tracks, prolonging winter storms in our region.
-Given all of these factors, and others not mentioned, I believe we are going to see a more normal Winter. What I mean to say is that we will see periods of cold and snow and ice storms, as well as some moderating/thawing periods with above normal temperatures
-I do believe we will have above average snowfall, and average to slightly-below temperatures in the Winter of 2016-2017.
-On average, I believe we could end up with 45-75 inches of snow in WMass depending on location and elevation.
-If you want to learn more details about some of the atmospheric components I raised above, please continue reading below for finer details.
-For those who just want a summary, I hope this was sufficient for you to get an idea of the whats and whys for our upcoming cold season.

INTRO DISCUSSION
With our extreme drought still in play, we could really use a mixed-bag Winter (in other words, more normal). Such a Winter would include cold snowy periods, milder thawing periods, and periods in between which tends to bring a mix of rain, ice and snows that have a higher moisture content (i.e. wetter and heavier). Now, these kinds of snows produce power outages, downed limbs and trees, and other human impacts. But in terms of the drought, it’s exactly what we need to help bring the water table back towards some form of balance.

SIBERIAN SNOW GROWTH
In October, we saw impressive snow growth in Siberia, and especially south of the 60N latitudinal line. A gentleman by the name Judah Cohen of AER (Atmospheric and Environmental Research) in Lexington, MA has been doing fabulous research work into discovering how Siberian snow growth and snow cover in October sets in motion a series of events that can bring cold and snowy outbreaks in the U.S. and many times right here in New England during the winter season.

Essentially the chain of events goes like this:
1. Snow growth increases rapidly in October over Siberia and blankets the region.
2. This deep snow pack, and cold air produces large, cold and strong high pressure in Siberia during the course of November
3. This large high pressure expands and acts like a block in the Troposphere (i.e. the lowest part of Earth’s atmosphere where our weather transpires). This block amplifies the jet stream, and weather systems begin to track meridionally (i.e. more south to north, rather than zonal which is west to east).
4. By a mechanism I don’t fully understand, this meridional flow tends to initiate something called “poleward heat flux and vertical wave propagation”. So what the hell does that mean, you ask? It means vertical waves of energy travel upward from the surface (i.e. the Troposphere) to many miles up in the sky (i.e. the Stratosphere). When this happens, it warms up parts of the lower Stratosphere.
5. When this warming of the Stratosphere happens near the North Pole, it weakens what is called the Polar Vortex, which is an area of permanent stratospheric low pressure that spins above the North Pole. This happens roughly in the December time period. Even though the Polar Vortex is generally strongest in the wintertime, when the Stratosphere warms, it weakens this normally tight circulation. So, instead of a tight counterclockwise circulation keeping the coldest air in the Stratosphere locked over the Arctic, a warming upper atmosphere causes this circulation to buckle and undulate.
6. Once we get into January, the wavy nature of the Polar Vortex up in the Stratosphere propagates downward into the Troposphere. This then impacts the Tropospheric reflection of the Polar Vortex – a Tropospheric circulation known as the Arctic Oscillation, or AO. The AO is a well known teleconnection (teleconnections are simply macro-scale, semi-permanent global weather patterns). It is one of the prime patterns responsible for how New England winters pan out for us here in western Massachusetts.
7. As we move into the heart of the winter, this now-wavy-and-buckling Arctic Oscillation pattern allows cold Arctic air to empty out of its icy gates at the Earth’s surface and down into the lower latitudes such as southern Canada and the United States.

I realize that this is a long explanation, but I raise these points to give you a context for my outlook this coming Winter. While the Polar Vortex fluctuates (as do all large-scale weather patterns, known as “teleconnections”), it went “negative” in late November and early December, and is expected to alter between a positive state in later December, and then possibly flip to a negative later in the Winter at least once more, if not a couple more times. This gives credence to the thinking that we will have periods of cold and snowy weather this Winter, with some moderating periods, too, during which ice storms and/or rainy thaws can visit our region.

TELECONNECTIONS
Now, to be sure, there are a number of other teleconnections that are more prime players when compared to others that help determine how our sensible weather will shake out over the course of the upcoming winter. Remember that in the Northern Hemisphere, the cold air outbreaks mentioned above can sometimes sweep down over the Eurasian continent, as opposed to the North American continent. This can be set in motion by other patterns such as the El Nino Southern Oscillation (ENSO), the Arctic Oscillation (AO), North Atlantic Oscillation (NAO), the East Pacific Oscillation (EPO), the and the Pacific Decadal Oscillation (PDO), to name several.

LA NINA/ENSO
This past Winter (2015-2016) we had the second strongest El Nino on record, which created a strong southern Pacific warm flow across the southeastern two-thirds of the nation. This knocked snow amounts way down, and kept the temperatures way up. This year, a weak La Nina is forecast, which favors more northern U.S. storm tracks with systems out of western Canada and the eastern Pacific Ocean. These La Ninas tend to favor periods of negative NAO, a/k/a Greenland blocking. With periods of cold air, a warmer western Atlantic, blocking in Greenland, we will likely see some Clipper systems move through New England bringing some light snowfalls. However, if some of these reach the coast, slow down, and develop rapidly, they could provide some solid snowstorms here. La Nina’s influence generally favors a good snow season for ski areas in central and Northern New England. La Nina can also bring rise to a southeast U.S. ridge of high pressure, so we’ll probably see intermittent strengthening of this feature, which will create periods of moderating temperatures.

ARCTIC OSCILLATION
The Arctic Oscillation refers to the permanent area of low pressure over the Arctic Circle at the surface and upper levels of the Troposphere. When it is in its positive phase, it’s a tight circulation that locks cold air over the Arctic. But when it weakens, it enters its negative phase. In fact, by the time you read this, we will have already experienced firsthand the effects of a weakened Arctic Oscillation. As the circulation weakens it becomes buckled and wavy, allowing cold Arctic air to spill into the lower latitudes of North America, which brought about a foot of snow between two systems that moved through western Massachusetts recently. Both the Arctic Oscillation and the North Atlantic Oscillation appear that they will transition into negative and positive phases this Winter, bringing cold and snowy periods, and some moderating, warmer periods.

NORTH ATLANTIC OSCILLATION
The North Atlantic Oscillation, or NAO, is a di-pole permanent global atmospheric pattern. It has two phases, negative and positive. When it is in its negative phase, you will find high pressure near Greenland to the northeast of Atlantic Canada, and low pressure down near the Azores Islands, which are a few hundred miles west of Portugal. This Greenland high pressure, with its clockwise circulation, encourages two effects that are important to us in New England. First, it helps drive a colder flow from the northeast to the southwest into New England. Secondly, it acts as a block in the flow of air leaving eastern North America. This can slow or even stall coastal storms near New England. With colder air draining down, and slower storms, we get snowstorms and Nor’easters here in western Massachusetts. The NAO is expected to go through some negative phases this Winter, which could help foster colder and more snowy conditions for our region.

EASTERN PACIFIC OSCILLATION
Like the North Atlantic Oscillation, the East Pacific Oscillation (a/k/a EPO) is the northern Pacific’s counterpart to the NAO. In this pattern, higher pressures form over Alaska, and lower pressures form to the east of the Hawaiian islands. This area of high pressure is sometimes the same high pressure system that forms over eastern Siberia in response to October snowpack, as discussed earlier. As we know, high pressure circulates clockwise. With a high located over Alaska, the flow around it can cause what is called cross-polar flow, and bring cold air from Siberia across the Arctic, and drive it south into Canada and the United States. Since air tends to move west to east in the Northern Hemisphere, this cold air can push east into our region, providing cold air for snow and ice storms to feed off of. As you can see in the embedded EPO graphic, we are in a negative phase currently

PACIFIC-DECADAL OSCILLATION
While the other teleconnections mentioned previously are atmospheric patterns, the PDO is an oceanic-based oscillation/pattern, that influences the air and atmosphere above it. A positive PDO cycle means warmer waters in the eastern Pacific. This year so far, we’ve got some warm water there, but there is a cooler pool of water on the southern region in which the PDO is measured. In 2013-2014, and 2014-2015 we had a very strong (i.e. positive) PDO, which helped foster a large, practically-stationary high pressure ridge above it. This clockwise-ciruclating feature kept causing cold Arctic air in northwest Canada to dive south and east right into the eastern half of the U.S. giving us plenty of cold to mix with storms to give us big snow and plenty of cold. This year, this feature looks mixed, and will encourage cold air at times, and at other times allow moderating temps in our region.

In other words, this Winter looks like a mixed bag of weather impacts, from mid-Winter thaws with rain or ice storms, to periods of Arctic outbreaks, light powdery Alberta Clippers, and some Clippers that redevelop into coastal bombs, and some legit southern-origin coastal Nor’easter snowstorms. In other words, a slightly above-average Winter in terms of snow and cold impacts.

Seasonal outlooks are broad brush strokes in a painting. For the fine-tuned details from day to day and week to week, please follow along each day on my Facebook (link this) page where I will keep you updated on how all of these impacts play out over the next several months.

CONCLUSION
It appears the heart of the coldest air will reside over the northern Plains and into the Great Lakes, Midwest and Ohio Valley this year. Here in New England, we will see cold cores move through, but will tend to be on the eastern edge of these coldest outbreaks of Arctic air.

This puts us right in the middle between the warmer Atlantic Ocean waters, and the coldest air to our north and west. Storms tend to form along these boundary lines between and warm and cold. That means we should see more in the way of coastal storms this season, as well as Alberta Clippers. Some of these storms could be slowed down during the negative phases of the North Atlantic Oscillation and drop more snow on us than they otherwise would.

I think that overall we’ll see just below or near average temperatures for the season, and average to above-average snowfall. Being so near to the warming ocean influence, we could also see some ice storms this season.

As you know, I will be covering our local weather every single day, noon and night during the Winter (and every day of the year), so please check in with my Facebook page for updated reports and information about impacts to your life and the lives of those you care about.

Thanks very much for reading!