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Winter 2013-14 forecast and discussion

Posted by David Epstein  December 3, 2013 01:05 PM

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Meteorological winter begins December 1st, meaning the next 90 days are the coldest of the year. For much of the country, the months of December, January and February also provide the bulk of snowfall for the winter season. During the winter I update the forecast as it changes on Twitter at @growingwisdom Please follow me there. Feel free to comment or ask questions too.

If you live in a cold climate, many want to know the forecast for the upcoming winter. Pure curiosity, budgeting for heat, a love of snow, a hatred of the white stuff or just to see if “they” get it right are all various reasons you may be interesting in what winter predictions are saying this year.

One of the aspects of winter, which isn’t part of the forecast, is perception. A winter colder than average, without a lot of snow, might be perceived by many as an easy one. Alternatively, a winter with a lot of snow, but milder than average, might go into your memory bank as having been horrible.

If you get into a car accident because of icy roads, it may cloud your recollection of the winter towards the harsher side. November certainly seemed like it was a very cold month and it was below aveage. However, the 2 degrees below normal was not in the top 10 coldest.

Winter forecasts are made for two main variables, precipitation and temperature. The official forecast, which calls for either of these variables to be above or below average, can be thrown way off by one big snowstorm or a week of super cold or extremely mild weather.

Long range forecasts are anything but perfect, however they are getting better. Once you get beyond a few days, one of the main drivers in the forecast becomes the many global circulation patterns which exist. Meteorologists call these long-term patterns teleconnections. These teleconnections “reflect large-scale changes in the atmospheric wave and jet stream movement, and influence temperature, rainfall, storm tracks, and jet stream location/ intensity over vast areas.”

These patterns fluctuate over various periods of time. Some patterns change on a weekly basis, while others can be more stable only fluctuating every few months, years or decades. The size of these patterns can be vast and their affects global in scope. Some patterns span the entire North Atlantic reaching to Europe, others are concentrated in the oceans south of the equatorial regions, while others are found in the arctic regions of the globe.

Not all patterns are present the entire year, some are and some only show up in certain months. Additionally, some of the patterns have a bigger effect on the winter months, while others are less a factor. Below is a list of many of the various patterns we know about. You can click on the names to link to an explanation of them if you are interested.

Prominent patterns over the North Atlantic
North Atlantic Oscillation (NAO), exists in all months.
East Atlantic Pattern (EA), exists in all months

Prominent patterns over Eurasia
East Atlantic/Western Russia pattern (EATL/WRUS), exists in all months
Scandinavia pattern (SCAND), exists in all months
Polar/Eurasia pattern , exists in all months

Prominent patterns over North Pacific/North America
West Pacific pattern (WP), exists in all months
East Pacific - North Pacific pattern (EP-NP), exists in all months
Pacific/North American pattern (PNA), exists in all months
Tropical/Northern Hemisphere pattern (TNH), during December-February
Pacific Transition pattern (PT),exists during August-September

Certain patterns are known to have a bigger influence on our weather here in New England than others. One of the more studied teleconnections is the NAO. When the NAO is negative we tend to be stormier and colder, when the NAO is positive we tend to have less severe winters. During the 1950s and through the winter of 1978/79, the NAO was mostly negative. A big change then occurred and the NAO went mostly positive. This is one reason so many winters in the 80s and early 90s were not so terrible.

Other planetary scale oscillations
In addition to these patterns, there are others like El Nino and La Nina which have a tremendous influence on our weather. Currently, the planet is showing a more neutral state where neither La Nino nor El Nino is very strong.

When forecasting the upcoming winter meteorologist looks for signals to see how all of these patterns may interact. In some winters, there are signals that many patterns are pushing the atmosphere towards a wet winter, while in other years the signals point to a dry, but mild winter.

Two winters ago many signs indicated a mild winter and that is exactly what happened. Last winter, several signals pointed to a snowy winter and we certainly had one. This year, the indications are somewhat murky, but point to less snow than last winter in New England, but a bit more in the mid-Atlantic. Philadelphia only had about 8 inches of snow last winter, but should better that this year.

For December, I am expecting the cold to relax somewhat after the middle towards the end month. In other words, it is possible the first part of December could be colder than the second half, this is likely the case in the upper Midwest. Long range.pngSnowfall appears limited for now, but just a slight change in the track of one storm can quickly give an area over 6 inches of snow, it doesn’t seem wise to say there won’t be much snow in December. Signals may point that way, but they just indicate trends, not a daily forecast.

The rest of the winter looks to be highly variable with fluctuations between deep cold and milder than average. Some of the long range maps have a very mild shot of air around Christmas, surrounded by two outbreaks of arctic air.

What I tend to be able to do with reasonable accuracy is forecast when we are entering a stormy or colder period and when we might be in more of a lull or thaw. For example, we know some very cold air will be entering the country this week and may end up affecting us around the 9th or 10th of the month. I don’t see any significant snow here in New England before mid-month.

Other Considerations
I am still concerned about being in a drought which would lend to a drier, but overall colder winter period. This is similar to the way the winter turned out a decade ago. Back in the winter of 2003 and 2004, we ended up with just over 30 inches of snow in Boston, below average while enduring weeks of below normal temperatures. It was so cold that some water main pipes broke due to the lack of snow which typically keeps the frost from penetrating too deeply.

December can be cold and often is, but we just haven’t had any real record breaking cold in over a generation. When you start seeing a long-term temperature trend like this, it’s highly unlikely it’s going to change this month. In Boston there have only been two record low temperatures in the twelfth month since 1943. One was set on a very cold morning the day after Christmas back in 1980. I clearly remember the morning; I was in New York City and noticed the windows where I was staying had layers of frost inside. The last low temperature record to be set in Boston was 25 years ago on the morning of the December 12th the low hit a bone chilling 2F.
Record lows December Boston.png
The number of snow/ice events and their size tends to be clustered in years. Once a snowy pattern takes hold, they tend to stick for about 6 weeks. If an area falls into a snowless pattern, that tends to stick as well. Finally, last winter ended up being very snowy. It’s very unusual to have two back to back significantly above average snow years, so this winter, while certainly having some snow, isn’t likely to be one you’ll remember for the final numbers.

This blog is not written or edited by Boston.com or the Boston Globe.
The author is solely responsible for the content.

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About the author

David Epstein has been a professional meteorologist and horticulturalist for three decades. David spent 16 years at WCVB in Boston and currently freelances for WGME in Portland, ME. In 2006, More »
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