top of page

Two Major Factors Will Help Determine New England's Weather This Winter

Updated: Nov 11, 2023

There will be two large-scale drivers of the weather for New England heading into this winter. These twp factors could ultimately determine how New England's weather plays out for most of this winter in both the temperature and storm departments.


EL-NINO


The first large-scale driver is the return of El-Nino. Without going into too much detail (as El-Nino has been widely publicized throughout the year), its basically a periodic warming of a strip of Pacific Ocean off the South American Coast. This warming can have affects on weather patterns around the world.


In the United States, El-Nino tends to have a heavy influence on the position of the polar and subtropical jet streams. The average position of the jet stream during El-Nino winters is shown below, along with typical impacts during the winter months. El-Nino has been in place since this spring, but its influence is most felt during the winter months.

As you'll notice, there is no label for expected conditions over New England. This is because of where the polar jet stream averages over the United States. You'll notice the polar jet stream is north of the United States over the western two-thirds of the county, but dives back down near New England.



Naturally, the coldest air of the winter is north of the jet stream, with milder air to the south of it. With the average position of the jet stream placed near or over New England, the region has a chance to end up on either the cold side or mild side more often than not, while the rest of the northern tier of the country has a better chance to end up on the warm side more often than not.


Before going further, it's important to note that the above graphic shows the average position of the jet stream, not where it will be locked in place all season. The jet stream is never locked in place, and is always shifting position.


While the above graphic shows where the jet stream could end up more often than not, it will not hold that position the entire season. There WILL be cold shots into the mid-west and Great Lakes regions. As for New England, the region will spend time on both the mild and cold sides. Which side New England ends up on more often than not may come down to El-Nino's strength.



EL-NINO STRENGTH MATTERS


While the average position of the jet stream over New England during an average El-Nino seems to be a toss up, there are distinct trends looking back at past El-Nino winters for New England. These trends come down to the event's strength.


Since 1950, there have been 25 winter seasons with an El-Nino influence. Of the 25 El-Nino events, nine have produced a generally above average winter for New England as a whole, another nine produced a generally below average winter and the remaining seven were near average. This even spread shows how New England can end up on either side of the average position of the jet stream.



Despite this, looking at the strength of the El-Nino event, trends begin to arise. Of the 25 El-Nino winters, six were considered to be strong, another six were considered to be moderate, while the remaining 13 were considered to be weak.



The six strong El-Nino events saw four above average winters (1957-58, 1997-98, 1982-83 & 2015-16) and two near average winters (1972-73 & 1991-92) for the region. In addition, three of these events were considered to be very strong. These events occurred during the winters of 1982-83, 1997-98 and 2015-16. These three El-Nino winters saw the three highest departures from average temperatures. The 2015-16 El-Nino was the strongest on record. That winter produced New England's warmest winter on record.


Departure from average temperatures during the three strongest El-Nino events since 1950, showing mild conditions dominating:


The weaker the El-Nino event, the colder New England's winters have trended. This is likely due to the fact that weaker El-Nino events (naturally) have less of an influence on the overall weather as stronger El-Nino events.



As of November 9, the NOAA's Climate Prediction Center has stated that the El-Nino is officially considered to be strong, with a greater than 55% chance of a strong El-Nino persisting through March 2024.


Earlier, we mentioned that a very strong El-Nino was being predicted by some publications, but that historic precedence doesn't support that happening. Right now, the Climate Prediction Center has given this El-Nino a 35% of becoming "historically strong." This lower percentage is indicative of the fact that history doesn't support this happening, but this percentage has gone up since the last update.



OUTLIERS


It's important to remember that there are many influences to the weather. Most of these influences can't be predicted months in advance like El-Nino. These other influences can have the power to override El-Nino's influences if they line up correctly. This can be seen in some outliers of the above trends.


One of the biggest outliers is the El-Nino event of the 1972-73 winter. This was one of the stronger El-Nino events and bordered on a very strong event. Despite this, New England saw near to slightly below average temperatures for the season. More notably, the Midwest, northern Rockies and Pacific Northwest also skewed a bit cooler than average. These areas typically see the most above average temperatures during El-Nino.


One of the biggest influences that can counteract El-Nino is the polar vortex, which is an area of low pressure typically centered around the North Pole. The polar vortex can send arctic shots of air southward into the United States when the polar jet stream is weaker and unstable.


This can occur when the North Atlantic Oscillation (NAO) is in a negative phase. A negative phase of NAO favors cooler, stormier weather across the east coast while a positive phase supports milder, more stable weather. Much of 2023 has seen NAO entrenched in a negative phase. How NAO plays out will have an impact on weather conditions, as will many other factors, not just El-Nino.


A graphic we used in our May 2023 monthly outlook pointing out the correlation between temperature and precipitation with the NAO index:



WARM OCEANS


The other major factor that will come into play for New England's weather this winter will be the abnormally warm ocean temperatures. These hot ocean temperatures were widely publicized to potentially help hurricane growth. While this is true, a warm ocean could also help wintertime nor'easters strengthen as well.


Nor'easters feed off the temperature contrast between warm air over the ocean and cold air over land. The higher the contrast, the more potential the storm has to strengthen. This is why blizzards typically strike New England toward the end of winter, in February and March. This contrast grows throughout the winter and typically reaches a climax at the end of winter.


The oceans have experienced record warmth through much of this year. This could help to enhance the strengthening potential for nor'easters. The El-Nino set up also promotes nor'easters to track near New England thanks to the average jet stream position. Both of these factors could help to create a large-scale snowstorm across the northeast this winter.



North Atlantic ocean temperatures by month and year. Each gray line represents a year starting from 1981. The orange line is 2022, the solid black line is 2023, showing record high temps:


Sea surface temperature departure from average showing warm oceans globally. You can also see El-Nino off the South American coast:



CONCLUSION


This isn't meant to be a seasonal outlook. There are many factors that go into determining the weather, most of which can't be predicted months (or weeks) in advance. This is breaking down two major players that will be in place. How those other factors play into these two factors remain to be seen.




67 views

Comments


bottom of page