The Winter of 2024/2025 is slowly approaching, so it’s time we look at everything we know about the upcoming cold weather season. There is an interesting development in the atmosphere and in the oceans, where the model forecasts do not agree with what the past indicators are showing.
We can already see how some of the large-scale global factors are developing. Looking at past data, we can look at how they change seasonally and how they have influenced winter weather in the past.
On the other hand, we have the model simulations or forecasts, which show a different story for the upcoming winter. The model forecasts tend to show a milder winter, but the historical data analysis shows something totally different, as you will see.
WINTER 2024/2025 MODEL FORECAST
We will start with the model forecasts. These are produced by long-range forecasting models or systems. These forecasting systems run a full simulation of the atmosphere based on known laws of physics but also include the oceans and ice.
These models are, of course, not perfect, and we never take them literally, but we just look at the developing trends. One of the issues is their coarse resolution compared to the real world. An issue is also that the starting condition of the model calculation can never be 100% fully accurate.
All these forecasts below are an average picture over three meteorological winter months (December-January-February) and show the general prevailing weather patterns.
The latest winter pressure pattern forecast from ECMWF shows a La Niña high-pressure system in the North Pacific and a broad low-pressure area from Canada into southern Greenland. A strong high-pressure area extends from the southern United States across the Atlantic and into mainland Europe.
Such a pressure pattern pushes the jet stream into the northern and northwestern United States. But over Europe, the jet stream is pushed further to the north, because of the high-pressure area over the continent.
Looking at the surface temperature forecast for Europe first, we see a warmer winter than normal over much of the continent. This is what we can expect due to the influence of the high-pressure system extending over the whole continent, as predicted by the model.
The precipitation forecast for Europe shows a drier season due to the high-pressure anomaly. Far northern parts of the continent show more precipitation than normal as the jet stream is forecast to move over this part. More precipitation is also seen over the south and southeast.
Over North America, the latest ECMWF winter forecast shows mostly warmer-than-normal temperatures over eastern Canada and the central, southern, and eastern United States. The warm anomaly gets weaker toward the northern parts of the United States.
The blue lines show a break in the above-average anomalies, indicating a potential route for cold air movement.
The latest precipitation forecast shows more precipitation is forecast over Canada and the northwestern and eastern United States. Less precipitation is forecast over the southwestern United States. With more precipitation and if cold air is available, this indicates more snowfall and a good snow season over the northern United States and Canada.
Looking also at monthly data for the upcoming winter, we have to mention the forecast for February 2025. It shows much less warm anomaly areas across the United States and Canada. Here, the normal to below-normal area is expanded from the northwestern United States into the central parts and over the Midwest and into the northeastern United States.
We can see the reason behind this if we look at the pressure pattern forecast for the same month, as seen in the image below. You can see a broad low-pressure area over eastern Canada, descending also into the northeastern United States. Image from weathermodels.com using a commercial forecaster license.
As the blue arrows indicate, that creates a northern flow from Canada down into the northern and eastern United States as the low-pressure area rotates counter-clockwise. This shows winter potential for the northern and eastern United States.
We will look at this development in the coming weeks as more data is available.
Now, going back to the 3-month average, we will look at the model forecast for the snowfall in the upcoming winter season.
WINTER 2024/2025 SNOWFALL FORECAST
Below is a special snowfall forecast from the ECMWF data. Looking over Europe first, you can see below-average snowfall over the whole continent, thanks to a high-pressure area. More snowfall than normal is forecast only over the far northern parts.
The snow forecast for North America shows a very double-edged picture. Most of the central, southern, and eastern United States are forecast with below-average snowfall. This is perhaps surprising, especially for the Midwest and the far Northeast, which can get more snow in a weak La Niña winter.
More snowfall is forecast for the northern United States and most of Canada. There is an area of below-normal snowfall over southeastern Canada.
We will soon release our new forecast article, dedicated to snowfall predictions. There, we analyze snowfall potential in more detail and provide a month-by-month breakdown.
But so far, we have mentioned this “La Niña” a few times, so it’s time we look at what it is and how it can shape the weather patterns this upcoming winter.
A COLD LA NINA APPEARS
La Niña is a cold phase of the large and powerful oceanic ENSO oscillation. It is a region of the tropical Pacific Ocean that shifts between cold and warm phases. The cold ENSO phase is called La Niña, and the warm phase is called El Niño.
Below is the late September ocean anomaly analysis. It shows colder-than-normal surface waters in the central and eastern ENSO regions (marked area). These cold anomalies have a “wave-like” shape. This is because of the strong easterly trade winds that push the waters towards the west, creating swirls on the ocean surface.
Below is an analysis/forecast image from NMME, which shows the ENSO ocean temperature drop as the warm phase ended in spring. Negative anomalies and cooling are forecast over the Autumn and Winter of 2024/2025. The forecast average is within the La Niña threshold but shows a weak to moderate event.
The image above shows that even in early spring, the ocean anomaly was still above normal but began cooling rapidly. Below is a high-resolution video animation that shows how the ocean went from warm to cold anomalies across the ENSO regions in the tropical Pacific.
La Niña usually creates a high-pressure system over the North Pacific. That promotes the development of a low-pressure region over Alaska and western Canada and shifts the jet stream downwards in between the two pressure systems.
The image below shows the shift of the jet stream into the northern United States. It shows the average position of the jet stream during La Niña winters and the resulting weather patterns over the United States and Canada.
The displaced jet stream brings colder temperatures and winter storms from the polar regions down into the northern and northwestern United States. Warmer and drier winter weather prevails over the southern states.
Colder air is more easily accessible to the northern United States, increasing the snowfall potential when moisture is available. The image below shows the average snowfall pattern for weak La Niña years, as expected for this Winter season.
In addition to the northwestern United States and the Midwest, there is increased snowfall potential over the northeastern United States and eastern Canada. This image is typical for a weak La Niña event, but every year has its own variations.
This data gives us enough confidence that we will see some influence from these anomalies over the coming cold weather season and looks contrary to what the model forecasts suggest.
And there is also another anomaly, but in the atmosphere, that together with the La Niña shows a very different image than what the models are suggesting for Winter 2024/2025.
ATMOSPHERIC WIND CHANGES
Like in the ocean, we again have a region that alternates between a positive and a negative phase. But instead of temperatures, we are now dealing with winds or, rather, their direction. This is called the Quasi-Biannial Oscillation, or simply QBO.
The QBO is a regular change in the winds high above the equator in the Stratosphere, alternating between easterly and westerly (zonal) winds. Strong winds in the stratosphere travel in a belt around the planet at the equator. And around every 17 months, these winds completely change direction.
The image below shows stratospheric wind data for the past 3 years. You can see how each wind phase descended over time. A negative/easterly phase was active in 2021/22, and a westerly in 2022/23. It was followed by another negative QBO phase last winter. The red arrows show the latest/current westerly wind phase descending in the stratosphere.
A radiosonde analysis from NASA also shows the wind direction above the tropics. It reveals the westerly winds around the 15-100mb level, which is in the stratosphere, confirming that the west QBO phase is active.
The QBO is deeply connected to the atmospheric motion and helps with the overall tropical forcing, including the La Niña. You could say that it also helps with the “communication” between the oceans and the Polar Vortex, which we will come to further down.
That is why one QBO phase does not mean a fixed weather situation, as a west QBO response can be different during a La Niña or an El Niño. So, we must look at the global weather system as a whole.
Below is an analysis of the winter pressure pattern during La Niña years, with the QBO going from easterly to westerly, just like this year. You can see a very blocked pattern, with a high-pressure area over Greenland and a low-pressure area over North America and Europe.
You can notice a lot of “older” winters in this mix of data, which tends to impact the temperature analysis below. Overall, there is a colder anomaly effect over the United States, Canada, and Europe. But many of these winters are several decades old and, of course, colder by default compared to the modern norm.
Still, these anomalies show what this combination means for winter patterns, and they clearly indicate a potential or support for normal to below normal temperatures during winter, opposite to the model forecast.
THE POLAR VORTEX
The best way to understand the Polar Vortex is to visualize it. In simple terms, it is just a name that describes the broad winter circulation over the northern (and southern) hemisphere.
Below, you can see a 3-dimensional image of the Polar Vortex to get a better idea. The vertical axis is greatly enhanced for better visual presentation. It shows the actual structure of the Polar Vortex and how it is connected down to the lower levels and the pressure systems.
The Polar Vortex extends over many layers of the atmosphere. The lowest layer is called the troposphere, where all weather events occur. But above that, we have the stratosphere, a deeper and drier level that is also home to the ozone layer.
We must monitor the state of the Polar Vortex because it can have a profound impact on our daily weather. We mainly separate the Polar Vortex into two different modes:
A strong/stable Polar Vortex usually means strong polar circulation and jet stream. This contains the colder air into the Arctic Circle, creating milder conditions for most of the United States.
In contrast, a weak/disrupted Polar Vortex creates a weak jet stream pattern. As a result, it has a harder time containing the cold air, which can now escape from the polar regions into the United States. Image by NOAA.
So, if you want cold and snow during Winter, and you live in the central or eastern United States, your odds are highest with a weak Polar Vortex. In nature, that means a heavy disruption of the jet stream and a release of cold air from the polar regions.
Historically, a La Niña winter has a 60-75% chance of producing a Stratospheric Warming Event (SSW), which is the ultimate Polar Vortex collapse event. It has produced them in the past and also in recent winters. The image below shows the typical SSW event frequency by month and by the ENSO event.
As you can see, a La Niña phase has a higher chance of producing a Polar Vortex collapse event. It usually produces one later in Winter, compared to an El Niño. Overall, this means that a La Niña event is unfavorable for a strong Polar Vortex, at least on average.
POLAR VORTEX AND WINTER
Currently, the Polar Vortex is running at its normal strength. But over the past few weeks, it was weak to even record weak for this time of year. This is rather unusual, but we can actually find another similar event in early October, dating back to the 1981/1982 season.
Below is NASA’s stratospheric wind analysis/forecast for the current 2024/2025 season. You can ignore the blue line, because it shows the last season. But you can see the purple line running at record-low values in the red-marked area.
Another such low autumn point for the Polar Vortex was in October 1981. Below is the same NASA analysis for that season. You can see the same pattern in October, with half the month running at record-low values. In early December, the stratospheric winds got reversed from a Sudden Stratospheric Warming event, which set the tone for the rest of Winter.
Below is the pressure anomaly pattern for the Winter of 1981/1982. You can see a high-pressure anomaly over the polar regions, similar to the other oceanic and atmospheric patterns we showed above in the article.
The low-pressure areas were strong and covered Canada and the United States and extended all the way over the Atlantic. This is a good winter setup for the northern and eastern United States.
Looking at the surface temperature analysis for the same period, we can see the expected image: cold air anomalies over much of Canada, expanding into the northern and eastern United States.
This is probably one of the more typical good winter scenarios for the eastern United States, largely aided by the Polar Vortex and its dynamics.
Of course, nobody can guarantee a cold winter or say that we will now have the same pattern in the upcoming Winter 2024/2025. But we are looking at how past anomalies and unusual developments have continued into the following Winter, reminding us how small changes can have a long-reaching impact.
We have now seen several different factors, all indicating a potentially colder pattern than models suggest in winter 2024/2025. That would mean a potential for some good winter weather across parts of the central and eastern United States and other parts of the mid-latitudes across the Northern Hemisphere.
For that reason, we constantly monitor the latest global weather patterns and their development. We are always trying to find signs and links to past weather patterns with it, perhaps even a glimpse of the future.
We will keep you updated on the global weather pattern development, so bookmark our page. Also, if you have seen this article in the Google App (Discover) feed, click the like button (♥) there to see more of our forecasts and our latest articles on weather and nature in general.