It’s been a while
since I talked about El Nino and other teleconnections. So, I wanted to talk about it again. As it will
be a bid deal going forward.
This post is
very long and will go into El Nino and how it’s evolving, it will also touch on the
historical impacts of El Nino based on overall strength. I will try to draw
some conclusions on what this could mean for winter 2026-2027.
What is
El Nino?
I’ve posted
many times what El Nino is and what defines a weak El Nino from a very strong
one.
But here is
a quick refresher.
The El Nino-Southern
Oscillation, or ENSO is a recurring Pacific climate pattern that shifts ocean
temperatures and disrupts tropical wind and ocean currents, weather patterns,
and temperatures across the globe. The ENSO consist of El Nino, Neutral, and La
Nina.
One way the
ENSO phase is diagnosed is by using observations of sea surface temperatures in
different regions of the equatorial Pacific Ocean. Sea surface temperature
(SST) departure from average in the Nino 3.4 region.
El Nino is
the warm phase of the ENSO. During an El Nino, western trade winds weaken in
the Pacific Ocean, this allows warm surface water to move west across the equatorial
Pacific towards South America. This allows the central and eastern tropical
Pacific Ocean to become warmer than average. That increased warmth can alter atmospheric
circulation and impact the position of the jet stream across North America.
The ENSO is considered
neutral when the Nino-3.4 index is +0.4°C to – 0.4°C
An El Nino is
very Strong if the Nino-3.4 index is over +2.0°C (nicknamed a "super"
El Nino).
Strong is
when the Nino-3.4 index is at least 1.5°C
Moderate is when
the Nino-3.4 index is at least +1.0°C
And weak is
when the Nino-3.4 index is at least +0.5°C
What’s
happening now with the El Nino
The 2026 El
Niño has moved beyond the “developing” stage. The Pacific Ocean and atmosphere
are now strongly coupled, and the latest multi-model forecasts show a rapidly
intensifying event that could rank among the strongest since modern records
began
As of 20
July 2026, the equatorial Pacific is warming: the weekly Nino-3.4 index stands
at +2.1 °C which is in El Nino territory, while the official three-month ONI
for Apr–Jun 2026 is +0.98 °C, which is showing a moderate El Nino. For this
reason, NOAA’s Climate Prediction Center has us in a El Nino Advisory in
effect. NOAA Issues this when El Nino or La Nina conditions are observed and
expected to continue. NOAA is giving El Nino a 97–99% chance of persisting and
strengthening through the upcoming winter, with a roughly 60% chance it reaches
“strong” territory in Nino-3.4.
Images from
the latest NOAA El Nino discussion
Another factor to think about.
Atlantic
Nino
The Atlantic
has something that is very similar to El Nino. This is called the Atlantic Nino
and is characterized by warmer-than-average sea surface temperatures (SST) in
the eastern equatorial basin and weaker-than-average trade winds throughout the
east-central equatorial Atlantic. The opposite is an Atlantic Nina and is
characterized by cooler-than-average sea surface temperatures (SST) in the
eastern equatorial basin. Like the ENSO the Atlantic Nino/Nina swings between
warm and cool phases every few years. In most years the temperature profile
between El Nino/La Nina is similar. Atlantic
Nino/Nina, where the two can be in the same warm phase, or they can have
opposite phases. The Atlantic Nino/Nina tends to be overall much weaker than
ENSO and has less impact on the Climate.
Strong
summer Atlantic Nino events are much more common than strong summer Atlantic
Nina events are uncommon. Those tropical
Atlantic SST are running around 1°C to 3°C below average across the Atlantic Nina
area. So, this is considered a strong event.
This summer
we’re seeing a very rare cooling event in the tropical Atlantic This has
emerged just as El Nino continues to strengthen in the Pacific.
The same
report said current with the cooling linked to strengthened trade-wind-driven
upwelling. Forecast output cited by Severe Weather Europe shows the cool
Atlantic anomaly lasting into late August, while Pacific El Niño anomalies
continue to intensify.
Satellite
shows that cold pool in the Atlantic, while it also shows that very warm El
Nino anomaly continues building across the Pacific.
El Nino’s
warmer-than-average waters in the Pacific can cause more sinking air over the
Atlantic and increase wind shear, which can lower Atlantic tropical activity.
At the same time, a cooler tropical Atlantic associated with Atlantic Ninna can
reduce the amount of heat and moisture available to fuel thunderstorms in one
of the key regions where hurricanes develop. With the El Nino in the Pacific
and the Nina in the Atlantic, could help farther suppress Atlantic hurricane
development this season. This could make the 2026 Atlantic hurricane season,
even quieter than we would expect even during a strong El Nino. But a quiet season doesn’t mean there can’t
be tropical impacts. 1992’s Hurricane Andrew is evidence of that.
If the
Atlantic Nino persist into Winter 2026–27; it will pair with a possible strong
El Nino. This could increase the risk for more frequent and intense winter
storms, with a mix of snow, ice, and rain depending on the timing of different
air masses. If this persists it could Increase
the chance for more of a stormy, wet winter in the Northeast and mid-Atlantic than
we would expect to see during El Nino. There is a chance it could extend the length
of the Northeast winter season into early spring.
Rest of
Summer into this Fall.
The
Northeast and northern Middle Atlantic region has already been seeing the
impacts of the developing El Nino. We’ve
seen an up and down pattern, but June and July has seen a few hot and very
humid stretches. an increase in severe
storms, that has resulted in quite a bit of flooding.
This kind of
pattern is typical during a developing El Nino.
With the El
Nino continuing to strengthen, it will have even more impact during the end of
Summer and Fall. So, the region will
experience more bouts of above-average warmth and humidity. which can sometimes
contribute to increased precipitation across the Northeast. I expect to see the
increased risk of frequent thunderstorms, due to the parade of frontal systems
to continue. This should allow the
northeast and Middle Atlantic region is see overall above average temperatures
and average to above average precipitation through the Fall. With the chance for heavy rain at times,
Possible flooding will be a concern. With the setup, the Northeast and Middle
Atlantic are going to continue to see severe weather outbreaks, as all this
evolves.
What
about Winter?
The Arctic
ice melt season is underway, and right now, sea ice extent over the Bering
Strait and Arctic Ocean is slightly lower than it was at this time last year. How much sea ice remains at the end of the
melt season remains to be seen. The
amount of ice will have an impact on winter 2026-2027. We will have to wait
until October to find out how the ice looks and how the snowpack builds in
Siberia for the answer.
Winter
impacts for this El Nino
How will the
ENSO impact our weather patterns across North America and specifically here in
the Northeast this upcoming winter? I will touch on the general winter outcome
during a strong El Nino.
The jet
stream is one of the biggest drivers of weather during the winter when it
drives major winter storm development.
Even with El
Nino, the colder air will return to North America, that temperature contrast is
going to lead to a screaming subtropical jet. During El Nino we also usually
see the northern Polar jet stream shoved well north into Canada. This helps
lock out that cold over northern Canada. The setup normally has the Pacific
storm track shift south. Which leads to increased precipitation across
California and the southern US into the Southeast. At the same time the
Northern half of the United States is prone to seeing warmer and dry conditions.
El Nino’s
Likely Impact on the Northeast and northern Mid-Atlantic this Winter
This El Nino
is expected to peak in late fall and early winter, making it one of the
strongest on record since 1950. The strongest El Nino’s on record were
1877–1878, 1982–1983, 1997–1998, 2015–2016. The El Nino of 1877–1878:
Considered the strongest El Nino ever recorded, while this currently El Nino is
expected to be very strong, there is still some uncertainly on that. But many
climate models are showing the 2026-2027 being at least as strong as the
1877–1878 if not stronger.
Looking at the strongest El Nino’s over the
last 44 years. We come up with 1982–1983, 1997–1998, 2015–2016. While no two El
Nino’s are the same, we can draw some general conclusions by looking at
temperature and precipitation anomalies from those years.
Temperature
trends
During El
Nino winters, the jet stream configuration typically brings warmer, drier air
from the Pacific into the Great Lakes and Northeast. This often results the
Northeast generally experiencing warmer-than-usual conditions. However,
precipitation patterns are much more unpredictable. Here’s an imaging showing
the typical El Nino pattern over North America.
Regional
differences
Coastal New
England: Warmer temperatures, more variable snow, and possible and wetter conditions
in some years.
Atlantic
coast: Warmer air masses from the Gulf Stream can keep coastal areas milder and
wetter in some winters.
Interior and
higher elevations: May see more snow than coastal areas, but still likely less
than normal for a strong El Nino year.
On average,
the stronger the El Nino episode, the warmer and wetter the winters have been
What does a
stronger El Nino typically mean for snowfall? The map below from NOAA shows how
far above and below average snowfall has been during a typical strong El Niño
January through March period.
You can see
quite a split in the Northeast. While much of the interior Northeast from
western Pennsylvania to parts of New England trend less snowy, parts of the
mid-Atlantic from southern New Jersey to Virginia and the southern Appalachians
have tended to be much snowier in a stronger El Niño winter.
Snowfall
departures from average during moderate to strong El Nino January-March
periods. Areas in brown typically have seen less snow, while those in blue have
seen more snow.
But it's not
just the strength of the El Nino. El Nino isn't the only factor influencing the
winter weather pattern. Other ingredients could throw a monkey wrench into this
snowfall scenario.
One of the
main reasons for this verbality has to do with high latitude blocking
(Greenland Blocking). This typically occurs during a negative NAO.
When high
pressure aloft forms near Greenland, it blocks the west-to-east flow of the jet
stream, forcing it to take a sharp southward plunge into the eastern U.S. This
pattern delivers ample cold air from Canada and sometimes is an instigator for
East Coast snowstorms.
How often
this pattern develops in any winter season is challenging to figure out months
ahead of time. But if it sets up frequently during a stronger El Nino winter,
parts of the Northeast can have a colder, snowier winter.
The area
of blocking high pressure near Greenland forces a southward plunge in the jet
stream across the eastern states when the North Atlantic Oscillation is in its
negative phase. This leads to persistent cold temperatures and the potential
for East Coast snowstorms.
Even a
stronger El Nino doesn't necessarily guarantee strong impacts on the weather
pattern.
Here’s what
the data shows. We examined seasonal snowfall totals during nine strong El Ninos
since 1950 for several Northeast cities.
When we break
down nine seasons into those which also had frequent Greenland blocking (three
seasons) and those that had a lack of blocking (six seasons). Admittedly, it's
a rather small sample size. There where big differences.
For the
Middle Atlantic Region
Both
Philadelphia and Washington, D.C., saw generally more snow on average in a
strong El Nino winter.
These
composites are further broken down by the strength (weak, moderate and strong)
of the El Nino episode. Based on the small dataset, there is some historical
correlation between the strength of the warming in the equatorial Pacific Ocean
and seasonal temperatures, precipitation, and snowfall locally at Washington
D.C. and Baltimore. Weak El Nino winters averaged below normal temperatures and
precipitation, while strong El Nino episodes averaged above normal temperatures
and precipitation. These findings can partly be linked to a stronger than average
sub-tropical jet that typically occurs during moderate to strong El Nino
winters, which would favor more active storm systems moving northward from the
south that draw warm, moist air northward as opposed to the drier Alberta
clippers from the northwest. Seasonal snowfall averaged above normal,
especially for moderate El Nino episodes.
Not all El
Nino winters are alike as many other shorter [e.g., North Atlantic Oscillation
(NAO), Pacific-North American Pattern (PNA)] and longer-term climate patterns
influence the local weather. For example, the moderate El Nino episode during
the 2009-10 winter was associated with record-breaking seasonal snowfall in the
mid-Atlantic region. Although it might seem (based on the 2009-10 winter) that
all moderate El Nino winters in Washington D.C. and Baltimore are linked to
above normal snowfall, these atmospheric quantities have been variable each
winter. Of the seven strong El Nino winters since 1950, four have been
associated with well above average snowfall while snowfall was virtually absent
in the other three winters.
I-95
Contrasts
Snowfall is generally less during a strong El Nino winter from New York City northward.
Boston saw an average reduction of almost 25% in snowfall during a strong El Nino.
It is typically a different story in the mid-Atlantic states. Both Philadelphia
and Washington, D.C., saw markedly more snow on average in a strong El Niño
winter.
Strong El Nino
winters with frequent Greenland blocking (labeled as -NAO in the graph below)
were much snowier than average in New York City, Philadelphia and Washington,
D.C. But, as alluded to earlier, there were only three such winters since 1950.
By contrast, strong El Ninos without much Greenland blocking were far less
snowy than average along the I-95 corridor.
Seasonal
snowfall during all strong El Ninos (yellow bars), strong El Ninos without
Greenland blocking (red bars), strong El Ninos with frequent Greenland blocking
(blue bars), compared to 1950-2023 average (gray bars) in four major Northeast
cities along the Interstate 95 corridor.
Interior
Northeast
Over the
rest of the Northeast, there was generally less snowfall during stronger El Ninos
in most areas, consistent with the map we showed earlier. Most of these areas
were saw similar ups and downs in snowfall due to strong El Nino winters with
frequent/little Greenland blocking, respectively. So strong El Nino with little
Greenland blocking saw lower snowfall amounts. The notable exception was in
northern Maine. While each strong El Nino exhibited an average reduction in
snowfall of around 10% in Caribou, Maine, the amount of Greenland blocking
didn't make much difference there. (I’m not really sure why)
Same as
the previous graph, but for interior Northeast cities from Pennsylvania to
Maine.
Will this
winter be a repeat of 1997-1998.
The super El
Nino brought unusually warm temperatures and below-normal snowfall across much
of the Northeast, with notable exceptions in the form of extreme ice storms
The winter
of 1997-1998 in New England and northern New York State was marked by extreme
ice storms and heavy snow at times, with the January 1998 ice storm being the
most catastrophic event. That ice storm was a series of five successive ice
storms hit northern New York, Vermont, New Hampshire, and Maine from Jan 5–9,
1998, Ice accumulations reached up to 4 inches in some areas of northern NY and
SE Canada, with 3/4–2 inches in northern New England. The winter of 1997–1998
in Pennsylvania was dominated by that strong El Nino event, which brought
unusually warm temperatures and below-normal snowfall across much of the state.
The Appalachians was a notable exception as they saw above to well above
average snowfall.
During the
winter of 1997-1998 the Coastal Plain and the I-95 saw very little snow.
Across the
northern Great Lakes, the 1997–98 El Nino’s, it was a very mild and dry winter,
with record-low ice cover and above-average lake temperatures, reduced lake
effect snow totals compared to normal years, making it a winter with unusually
weak LES for the area.
The 1997–98
saw the lowest Great Lakes ice cover over the lakes since systematic records
began in 1960.
The snowbelt
regions downwind of Lake Erie and Lake Ontario, likely will be cold enough at
times to get lake effect snowstorms, Past winters that featured a strong El
Nino saw average to slightly below average snowfall. But do the variable
temperature pattern it was hard to keep much of a snowpack. Winter 2026-2027
could see a similar problem. But while the first part of the winter was extremely
snow free. There was a huge lake‑effect snow event in Tug Hill during
the 1997–1998 winter. It occurred on January 11–12, 1997, when a massive storm
produced a 77‑inch, 24‑hour snowfall at Montague, NY National Centers for
Environmental Information. This was the highest recorded 24‑hour snowfall in the United States at the time, but a federal
review committee later concluded it did not meet official standards for a
national record Rutgers University Climate Lab.
1997-98 saw
very little snow in the coastal Plain of the Middle Atlantic and New England.
The I-95 corridor ended up with very little snow. For the winter season from
December 1997 through February 1998, Washington, D.C. recorded only 0.1 inches
of snow for the entire season, Philadelphia recorded a total of 0.8 inches of
snow for the season, NYC’s total for the entire winter was 5.5 inches. Boston
ended up better with Boston recorded 56.8 inches. Much of this is the result of
late season blizzards.
For
Maryland, the 1997–1998 winter was mild and wetter than normal, with
above-average temperatures and precipitation. The El Niño climate pattern
brought a generally warmer, wetter season, with only occasional cold snaps and
snow events. The region avoided the extreme cold or flooding seen in other
parts of the country, but residents experienced more rain and occasional icy
conditions.
What does
all of this tell us about this winter?
Here is a
look at a typical winter pattern during El Nino
NOAA has
released their 3-month forecast for December, January, and February across the
United States from 2026 to 2027. The forecast calls for above average
temperatures and below average.
Precipitation for the northern half of the United States,
above average precipitation and near normal temperatures for the southern half.
Summary
Above-normal
temperatures are favored across much of the East. This could increase the
frequency of rain or mixed precipitation at lower elevations, but it does not
rule out major snowstorms.
A strong
southern jet stream can provide moisture for East Coast storms. If enough cold
air is available, that moisture can produce a significant nor’easter. Without
sustained cold, the same storm track may produce rain along the coast and snow
farther inland or at higher elevations. Other very strong El Ninos have experienced
things like this.
If this El
Nino reaches its projected strength, the Northeast is likely to be milder and
drier than average, with warmer temperatures and reduced snowfall compared to
recent years. However, the exact outcome depends on the timing and strength of
the jet stream, so forecasts will be updated as the season approaches.
Parts of the
Great Lakes sit near where that drier northern signal is expected to setup,
while the Mid-Atlantic and portions of the eastern United States are closer to
the wetter southern storm track.
The snowbelt
regions downwind of Lake Erie and Lake Ontario, likely will be cold enough at
times to get lake effect snowstorms, Past winters that featured a strong El
Nino saw average to slightly below average snowfall. But due to variable
temperature patterns it was hard to keep much of a snowpack. Winter 2026-2027
could see a similar problem.
Coastal New
England: Warmer temperatures, more variable snow, and possible and wetter
conditions in some years.
Atlantic
coast: Warmer air masses from the Gulf Stream can keep coastal areas milder and
wetter in some winters.
Middle Atlantic
Coast and I-95 corridor from Washington DC to Boston, will likely see a milder
winter with average to lower-than-average snowfall, but that will depend on how
strong El Nino gets.
Interior and
higher elevations: May see more snow than coastal areas, but still likely less
than average if this is indeed a strong El Nino year.
Depending on
the timing of particular setups, several Ice storms are on the table. One or
two of these could be crippling like we saw in 1998.
The
snowbelts off of Lake Erie and Lake Ontario, could see average to slightly
below average overall snowfall. But with frequent times of milder temperatures a
deep snowpack might be hard to come-by.
I know the hype
just about everywhere is talking about super El Nino and this being the
strongest in record history, signaling doom and gloom with massive impacts. But
as I’ve shown many other variables can alter things. While a very strong super El Nino is very
possible, there is still a chance it won’t end up as strong as people think. Over
the next several months we will see how things trend.
I hope you
found this post interesting and educational. Please leave a comment on what you
thought. And if you liked it, let others know and see it.
I will
likely release the first outlook post on the 2026-2027 winter sometime in
October.
