Why are winters so warm in the Northeast?

Some of y’all have been asking why this past winter was so warm with a lack of blocking and snowfall. I’m sure many of Y’all have the same question. So here is a post that will try to explain what is going on. I’m a Meteorologist not a Climatologist. But I do have an understanding of Climatology, so we will see how well I do!   

I’ve been posting a few writeups dealing with the changing climate, in things like the spring and hurricane outlooks. This post will take a look at possible reasons for last winter being so warm and snowless.   

 El Nino Southern Osculation (ENSO)…

 

 

 

When we look back at Sea Surface Temperatures on the 13th of February and compare that to now, we can see there have been a lot of changes in the ENSO region of the equatorial Pacific.  Nino region 1+2 and in Nino region 3 is starting to cool.  Looking at the subsurface water temperatures anomalies, we can see there is a lot of cooler water just below the surface. 

 

During the last 4 weeks, above-average SSTs have weakened across most of the equatorial Pacific Ocean

So, this El Nino is going to flip to La Nina conditions very quickly. 

 During this winter, I received questions or saw statements, about how the ENSO doesn’t seem to matter, in spite of it being a El Nino or a La Nina, all we’re seeing is warm snowless winters here in the Northeast. And those observations have been correct.  Over at least the last 6 years winters have been quite warm. So, the question, why is that is valid?

I’ve mentioned The Tonga’s Hunga volcanic eruption that happened in 2022 many times. It released an enormous amount of water vapor into the atmosphere. The shear amount of water vapor is in part to blame for the recent warming in the Northern Hemisphere. The water vapor is going to continue to cause havoc for several more years.  But the volcanic eruption can’t account for the last several years of warm winters. So, what else is going on?

To answer that we have to look at the state of the Pacific and Atlantic.

We’ve had a positive Pacific Decadal Oscillation (PDO) for the last few years.  We also have warm SSTs north of the ENSO regions. All of this constitutes mixed signals.  Helping to counter what’s going on inside the ENSO regions.

The Atlantic is also very warm. The tropical Atlantic is experiencing well above average SST.

During El Nino/La Nina there are characteristics that are expected, take for example my winter outlook, I based things on the strong El Nino, the overall pattern did resemble what you would expect for an El Nino. But activity in the subtropical jet has been slightly out of what you would expect. Why is that?

 

The El Nino hasn’t exerted much influence on the atmosphere. Based on Oceanic Nino Index (ONI) [The ONI is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO] tropical SSTs, Nino 3.4 showed a strong El Nino over the Winter. But the Southern Osculation Index (SOI) hasn’t responded like it should have.  The SOI has been indicating a weak to moderate El Nino. This disconnect is very important, as what was going on with the Pacific SST, where the El Nino wasn’t really coupling with the atmosphere, which threw off the tropical forcing.

Based on the data in a paper by Michelle L. L’Heureux with the Climate Prediction Center (CPC), we could see La Nina begin around mid-May. I won’t get into the research in the paper, but if you want to read it, here is a link to the paper.

A Relative Sea Surface Temperature Index for Classifying ENSO Events in a Changing Climate.

The CPC images, do agree with that.

Here is my theory…

The Atlantic is the other side of the issue. It is quite possibly the bigger part of the equation.  The super warm SST in the Atlantic is playing havoc with teleconnections like the Artic Oscillation (AO) and North Atlantic Oscillation (NAO). The warm waters are affecting the polar jet stream and promoting troughing in the west and ridging in the east, this is one reason why the western CONUS has been experiencing colder winters over the last several years. The much warmer than usual water in the Atlantic, is most likely having an impact on the Atlantic Meridional Overturning Circulation (AMOC). The AMOC is like a conveyor belt, where the warm salty water in the tropical Atlantic flows north, meets the colder water in the northern Atlantic, which allows the warm water to cool and become denser and sinks, then this colder air moves south as deeper currents along the North American Coast. All of this explains the very warm water in the Gulf of Maine, and along the Middle Atlantic Coast. This circulating water has a cascading impact around the globe and is a big player in world climate.

 

The AMOC has an effect on the Atlantic Multidecadal Oscillation as well. The last few winters haven’t had a lot of high latitude blocking near Greenland. The poleward moisture and heat transport from the tropics is affecting the NAO and AO.  Since blocking most of the time coincides with negative phases of the NAO and AO. The blocking helps the Northeast experience cold during the winter, and helps improve snowfall across the region. The warming is interfering with the sub polar low and the subtropical high making both stronger than average. This is allowing the NAO to stay in a persistent positive phase. When the NAO is positive, the Northeast is much more likely to see a warmer winter. Subsequently the high latitude blocking is influenced by many oscillations. All of this is influencing storm tracks and is altering wind patterns. This in turn is affecting seasonal temperatures in the Northeast. So the pattern becomes slightly out of tune, making things warmer; along with a storm track that makes it much harder for things to phase, which makes having big snowstorms more difficult.

There is no doubt that the global climate is warming. Since the 1980’s a large part of the CONUS has been trending warmer. The Northeast is one of the fastest warming regions, but it’s the Arctic that’s seeing the most warming. This warming is melting sea ice.  The melted ice flows into the Atlantic, this fresh water dilutes the saltiness, which impacts the AMOC. Research has shown that the AMOC is losing stability and is slowing Down. The warming Atlantic Ocean water has a big hand in making northeast winters milder, much like drought begets drought, our warming winters feed on themselves. The lack of ice and snow, ends up reflecting sunlight back to space, so the ground absorbs more heat, driving temperatures higher. As a result, there are higher odds of a storm bringing rain instead of snow.

There are examples in the past, that show this same general pattern. One of these is the Medieval Warm Period that occurred around 900 A.D. to the mid 1300’s.   A.D.  Increased solar activity and a decrease in volcanic activity, brought about changes in the NAO, which brought about warmer winters and wetter conditions to Europe and eastern North America. Core samples show that Nordic Seas became well above average. The very warm water caused a lot of ice loss in the arctic. As we’re seeing now, this melted ice worked its way into the Atlantic, the fresh water from the melted ice, eventually cooled the ocean which resulted in the AMOC Slowing down and then collapsing. So, the very warm conditions in the late 1300s quickly turn to unprecedented cold conditions in the early 1400s, only two decades later. We know this through core samples and tree rings. This was the beginning of the Little Ice Age, which lasted roughly from the 1400’s to the end of the 1800’s or beginning of the 1900’s.

I’m not saying what’s happening now is going to lead to an event like the Little Ice Age. I’m just drawing a parallel between what looks to be going on and a similar event in the past.  This means winter here in the Northeast is going to continue to be a casualty of what’s going on for the foreseeable future we're still going to get these snowy storms, but very snowy winters are going to become harder and harder to occur.

There is a lot of debate about natural factors causing all of this VS humankind causing all the warming. But regardless of which side you take, we’re stuck with the fact that the climate is warming. And this warming is not only impacting the climate but also the weather.   

IMO a lot of what is going on with the warming has to do with natural cycles and water vapor. I’ve never said that humankind isn’t lending a helping hand. There is no doubt that part of the warming climate is due to human activities. But I think a large part of what is going on is the ocean/atmosphere system and cycles, many of which we know nothing about. I’ve posted many blog post on this subject. You can find them in the blog.

All of this makes longer range forecasting challenging. we're going to have to adapt to the changes that are going on. This is a steep learning curve. We can still use past events to forecast. But we're going to have to alter the rules and tweak things a bit.