A new warming wave in the stratosphere will begin, putting pressure on the Polar Vortex. Strong weather patterns in North Pacific and North Atlantic will trigger the warming, which will help to lock down the colder weather across North America.
The Polar Vortex plays a key role during the cold season. It is strongly connected from the ground to the higher levels of atmosphere. The weather can be affected by any significant change or disruption caused by the Polar Vortex.
We pay close attention to the activity in the stratosphere, and monitor it frequently. Before we explain what’s up with the Polar Vortex or our weather, let’s quickly cover some basics: What is the Polar Vortex? How does it form? And why is it so important.
This is what we try to explain in all of our winter articles. This is an important aspect of winter season. Understanding the larger picture of weather can help you understand how it really is global.
HIGH OVER THE NORT POLE
As we enter autumn, the sun starts to wane in the polar regions. This means that the north pole begins to cool down. The atmosphere further south remains warm even though the polar areas are cooling. It continues to receive energy form the Sun. On the image below, you can see that the polar regions receive very little solar energy compared to those further south.
As the temperature drops in the polar regions, the pressure also drops. As the temperature drops towards the pole, and the temperature difference towards south increases, a large low-pressure, or cyclonic, circulation begins to develop across Northern Hemisphere. It originates from the top layers of the stratosphere. This is known as the Polar Vortex.
But where is this stratosphere located? The troposphere, the lowest layer in the atmosphere, is where all weather takes place. It can reach up to 8 km (5 miles), above the polar regions, and up to 14-16 km (9-10 mi) above the equator.
Above it is the stratosphere, a deeper layer. This layer is approximately 30 km/18.5mi thick and very dry. This is the location of the Ozone layer. The image below shows the layers of the atmosphere. You can see the troposphere and weather at the bottom, and the stratosphere above it.
These layers are very important, because when you hear meteorologists talk about the polar vortex and its influence, in most cases they mean the higher altitude – stratospheric part. The entire polar vortex covers the atmosphere’s bottom half, from the ground up.
Although the stratospheric vortex is spinning above our weather, it is still directly linked to the lower levels. It can shape our daily weather in one of several ways as one large circulation that covers the entire hemisphere.
The image below shows a typical Polar Vortex at 30km/18.5miles altitude (10mb) in the middle stratosphere during winter season.
The polar vortex is essentially a very large cyclone that covers the entire northern pole and down to the mid-latitudes. It is strong at all levels, but can take on different forms at different altitudes.
Below is the polar vortex at an even lower altitude of around 5km/3miles. It shows the true size and shape of the polar vortex closer (cold colors). The terrain/ground influence, as well as the dynamics of various weather fronts and systems, makes the polar vortex more deformed, the closer you get to the ground.
Be aware of its “arms” extending into the lower latitudes, bringing along colder air and snowfall into the mid-latitudes. These arms can also generate a lot of energy, which can lead to strong winter storms in the United States (Noreasters) or in the North Atlantic (strong wind storms).
We have created a high-resolution video below that will give you an even better idea. It shows the Polar Vortex spinning at 30km/18.5miles above the Northern Hemisphere.
Video showing the December 2020 to January 2021 period. This video was made using NASA GEOS-5 data. We used the vorticity parameter to show the energy from the polar vortex. You can see that the polar vortex covers a large portion of the Northern Hemisphere. You can see how the “anti-vortex”, deformed and attacked the Polar Vortex, spinning in the opposite (clockwise) direction over the North Pacific.
The main message of the video is that the Polar Vortex does not consist of one winter storm that moves from the Midwest to the Northeastern United States. It is a large cyclonic area spinning over the entire Northern Hemisphere at almost 50km/31miles elevation, and beyond.
A strong polar vortexThis means that there is strong polar circulation at all levels. This can lock the cold air in the Polar regions, creating milder winters in the United States and Europe.
On the other side, a Polar Vortex collapseIt sounds just as dynamic and dynamic as it is. Higher pressure crashes from the stratosphere onto the surface, releasing colder atmosphere out of the polar areas into the United States or Europe. Image by NOAA.
A rise in temperature or pressure in the stratosphere is usually what causes a polar vortex to collapse. This is called a Sudden Stratospheric Warming. It is a sudden rise in stratospheric temperatures, as the name suggests.
Below, you will find out more about the SSW events. You’ll also see how the SSW event of January 2021 changed the course and character of the Winter season one year ago.
However, there are smaller warming waves in stratosphere that do not cause the polar vortex to collapse. They can sometimes displace the polar vortex enough that it is less influential on the surface. This can allow for other factors to take control and temporarily create a new weather pattern.
POLAR VORTEX – WARMING WAVE EARLY IN 2022
We typically view the polar vortex at the 10mb level in the stratosphere. It is about 28-32km (17-20 mile) in altitude. This altitude is considered the middle of stratosphere. It gives a good representation about the general dynamics of stratospheric vortex and its downward link.
The strength of the polar vortex can be measured by the strength of its winds. Usually, this is done is by measuring the zonal (west to east) wind speeds around the polar circle (60°N latitude). Below is an ensemble forecast for 10mb winds.
The polar vortex is at the 10mb level, which is much stronger than usual for this time of year. It is expected to stay at a strong level with slight oscillations in between.
The actual map shows that the stratospheric Polar Vortex appears to be in a good place. It doesn’t have the classical circular appearance, as it is more oval. But it does have a stable wind field. It is located in the North Pacific and has a semi-persistent high pressure area. This is pushing against it, creating its oval shape.
The temperature at this level shows a wide cold-core over North America and the Arctic. We can see the North Pacific high pressure, with some weak temperature anomalies surrounding the cold core. Despite this, it is still a fairly stable Polar Vortex.
But is the strong stratospheric Polar Vortex actually affecting our weather? It is not, and it is unable to. Despite being strong, it has had difficulty lately exerting any significant large-scale influence in the Northern Hemisphere. But that does not mean that it won’t have local weather “connections”.
We can see a fascinating progression in the pressure anomalies across the polar regions during the last three months. Below is an image that shows pressure anomalies from surface to upper stratosphere.
The strong low-pressure buildup observed in the stratosphere in late November is striking. This was a strong polar vortex that connected easily to the surface in early December. However, strong high-pressure anomalies, which fight against the stratosphere and limit its weather influence, have been emerging around and above the polar circle.
This is easily seen if you look at the 7-day forecast for sea-level pressure anomalies in the Northern Hemisphere. The high-pressure anomaly that covers most of the Polar regions is striking. This is a strong blocked weather pattern that deflects the influence of the stratosphere.
This is basically a disruption of lower-level polar circulation. Below is a temperature forecast that shows cold air anomalies expanding southward from western Canada to the United States. This is due to the jet stream being pushed south. The cold air is not reaching Europe’s mainlands due to a local high pressure pattern.
You can also view the forecast vertical pressure profile. The image below shows the pressure anomalies with altitude over the North Hemisphere (40-80°N). As low-pressure anomalies (cold colours) in the stratosphere, we can see the strong Polar Vortex. The low-pressure anomalies are extending down, but have a hard time finding a clear “grip” on the pressure systems in the lower levels. Some connection may be found over North America.
This is due to the large-scale effects of the tropical oceans on the atmosphere. These effects were already detected by the long-range forecasts for Fall. These strong pressure changes have allowed for the rise of a strong high pressure system from the North Pacific to the Arctic Circle.
This illustrates how the atmosphere at lower levels can determine their future, regardless if there is a strong polar vortex. The story doesn’t end there. In fact, this disrupted weather flow at the lower levels means that a lot energy is being involved and must go somewhere or everywhere.
WHEN WEATHER ENERGY GROWS UP
These powerful pressure systems can interact with each other and exert a lot more energy upwards into stratosphere. This is a very well-known process, also called “vertical wave activity”.
You can see vertical wave propagation in action on the image below. First, strong weather systems deflect a lot energy upwards into stratosphere. Later, that energy can cause a disruption to the polar Vortex, causing a warming event and collapsing it. The energy is returned to the surface by the collapsed Polar Vortex, altering the jet stream position and changing weather patterns.
The ECMWF forecast for January shows that the block pattern will continue. High pressure is dominating the North Pacific, extending into Arctic Circle and disrupting the flow like a rock in a pond. The North Atlantic also has a low-high/low pressure pattern that can send decent energy into space.
The next map below shows how we can track the wave activity and energy around the Northern Hemisphere. It shows the heat exchange flow at the border of the troposphere to the stratosphere. Strong wave activity can be seen in the North Pacific as well as the North Atlantic due to the high pressure systems sending a lot of energy up.
POLAR VORTEX WARMING WAV
These strong dynamics are generating energy at higher levels than they do at lower levels. Below is the 10mb Polar Vortex Forecast, which shows a warming trend that extends from Europe over Siberia. This is due to the strong disruptions that occur below, which can often kickstart a major stratospheric heating event.
The warming wave is good and is accompanied by a high-pressure region in the stratosphere, pushing against Polar Vortex. The forecast below shows that the core of the Polar Vortex is moving over Greenland, while still maintaining a good shape, and strong wind field. However, it is being moved from its normal location.
The ensemble forecast diagnostics shows the temperature waves around Polar Vortex at 10mb (30km/18.5mi). First, we will have a double-temperature wave (wave-2), but then we will have a single temperature wave in round 2. The second round towards mid-month seems weaker than the previous one.
The first round won’t last long as the warming will begin to fade in the days ahead. Although we will see some movement and a decent push of the polar vortex it will soon push back.
The structure of the polar vortex is now very elongated. Below is a 3D vertical analysis that shows North America’s elongation. This is the point of contact as seen in the vertical analysis. It will play a part in maintaining/powering the low-pressure region and the cold temperatures over North America. This is more of an area effect than a large-scale impact.
It is expected to maintain its circular shape for a few more days, creating a stronger zonal field. The high-pressure area in eastern Asia will briefly decrease. However, a new warming wave will start in the same area, from Europe to Siberia. This is because lower-level pressure patterns continue to send energy upwards.
It is unclear how strong this second wave of warming will be as there is lots of variability in the forecast for that time period. We can put this activity in perspective with a special graphic.
Next, notice the high pressure anomaly rising up from below. This anomaly reaches up into the lower stratosphere beginning in December and blocking the influence of the top-down. The forecast part of this graphic shows more high pressure activity from below. Additionally, high-pressure anomalies are beginning to appear in stratosphere due to warming activity.
This indicates that weather pattern disruption will continue for the most part without any major interference from the stratospheric vortex downwards. The mid-month forecast below shows that there is strong high pressure in the North Pacific, which extends into the Arctic Circle. This causes the jet stream over North America to drop, bringing cooler air.
The central North Atlantic will see a high-pressure region. The strong low-pressure area over North America is amplifying it. This does allow for cold air to descend into Europe as the westerly flow is being weakened.
The temperature forecast below shows that the cold air is descending from Canada to the United States due to the weakening lower-level polar vortex. These pressure anomalies are more a side effect of the warming wave in stratosphere than they are the driving force.
It is amazing to see how, despite strong stratospheric vortex, lower level weather patterns were able withstand it and fight back. These strong dynamics often bring wild weather. The official NOAA 8-14-day forecast for the United States shows this. With the exception of the eastern and far southern states, colder temperatures will prevail across most of the country.
The extended polar vortex forecast shows that the ensembles are not subject to major disruptions, except for one member. The forecast suggests a more or lesser stable stratospheric-polar vortex. Without more warming waves, it is likely a matter of time, before the strong polar vortex can finally find its “ground”, taking over the weather patterns of the Northern Hemisphere.
ECMWF EXTENDED NOW
We can see the current warming trend over Eurasia in the extended range forecast by ECMWF. It will be visible towards the middle of the next month. Below is an ensemble forecast showing the temperature anomaly at 10mb (30km/18.5miles).
This confirms the possibility of some disruption by the polar vortex in the days ahead, but it will not have any immediate effect, as we now know.
We can see that the warm signal has disappeared and that colder anomalies have taken over. This means that the polar vortex is expected to recover and maintain its dominance. Extended forecasts are not perfect so we will only be looking at the trends in this range. Sometimes new dynamics can grab hold of it with some delay.
It is difficult to know at this time what specific weather effects could result from such situations. These events and their effects can be unpredictable. The model must be able to accurately forecast the surface, and then add the effects from above.
Below is a ECMWF extended prediction for pressure anomalies in late January. It does show lower pressure anomalies across much of the Arctic, Greenland and Greenland. This could be an indication of a connection between the strong stratospheric Polar Vortex and the lower levels.
Below you will find the ECMWF extended -range stratospheric Wind Speed Forecast. It also shows the wind speed for the polar vortex. This is directly related to its strength. The polar vortex should remain strong and stable throughout January. There are fluctuations but no signs of major warming, or disruption.
Last is the best example of a warming/disruption phenomenon changing the course and duration of Winter. Winter. The following video will show you how the major stratospheric event of collapse began exactly one year ago. It altered the weather patterns in the North Hemisphere between January 2021 and February 2021. It was later discovered to be the main reason for the strong cold epidemic in the southern United States in February.
MAJOR WINTER STRATEPHHERIC WARMING
Officially, a major polar vortex disruption/collapse has been named Sudden Stratospheric WarmingEvent (SSW). It is exactly as the name implies. A sudden increase in temperature in the polar atmosphere during the cold season. The stratosphere can warm up, causing the polar vortex to weaken. It can also collapse under rising pressure during prolonged warming events.
The energy from the lower layers is usually the source of the warming. Strong weather systems can deflect large amounts of energy upwards into stratosphere, disrupting its dynamics.
This disruption causes a chain reaction which can shift the jet stream and create a high-pressure zone over the Arctic circle. An anomaly like this can release cold arctic ice into Europe or the United States. Below are two examples of major warming events, both from ESRL/NOAA. The image below shows the SSW events that occurred during the 1984/1985, 2008/2009 winter season.
The top row shows stratospheric conditions. It includes warming anomalies (shaded), as well as a polar vortex which collapsed and was divided into two parts. (black contours). The bottom row shows temperature anomalies at the surface that occurred after these events. It led to the very cold winter in early 1985 and cooler temperatures after the 2009 SSW event.
The 1985 warming event can be seen in a closer view. It shows the stratospheric heating (red colors) that progressed downwards over the years. It quickly connected with the lower layers of atmosphere, increasing pressure above the North Pole in mid January and into February. This event triggered a pattern shift and released colder air to the north and central United States.
Below you will see the surface temperature anomalies following the 0-30 day SSW event in 1985. The signal is very cold from northern and central Europe, and it is also cold over most of the United States. Due to the strong stratospheric warming event, the western polar areas were warmer than usual.
Combining all Stratospheric Warming events over the past decade and looking at the weather 0-30 day after these events gives us an interesting picture.
Below is the average temperature for 0-30 days following an SSW event. The United States has a lower signal than Europe and Siberia. Note: This is an average image of many SSW-related events. Each warming event is unique and does not necessarily indicate a strong winter pattern.
Below are the average pressure anomalies, which indicate the Polar pressure increase following an SSW. The pressure tends drop over Europe, the western Atlantic and other parts of the world. This is due to a highly disrupted circulation. It allows colder polar breezes to move freely out of the polar regions.
The snow anomalies below show that there has been an above-average amount of snowfall in much of the eastern United States as well as Europe. This is normal after major warming events as the colder air has a more direct path to the south and into these areas.
POLAR VORTEX WARMING EVENING OF 2021
One year ago, in the late December or early January, we witnessed a major event in the stratosphere. The whole sequence started just before the new year. It changed the weather patterns for the remainder of Winter.
The polar vortex was very strong in early December. It reached speeds of over 40m/s (90 mph) zonal wind speeds. The polar vortex began a slow decline towards the middle of the month and in some cases even later in December. NASA has provided a graph that shows how the zonal winds became negative in January due to the collapse of the polar vortex.
The temperatures at the 10mb level are shown in the next images. It is located at 30km/18.5miles above the sea level. The polar vortex here is more circular. This is due in part to the lower direct influence of the terrain or the weather fronts/systems.
In December, a warming trend began in the stratosphere. It spread from Europe into central Asia. It was beginning to engulf outer layers in the polar vortex. As the pressure began to rise in the North Pacific and east Asia, the shape of the cold-core of polar vortex was becoming more oval.
Just two days later, the warming wave reached a strong peak over Siberia, with maximum temperatures in the wave reaching up to +5°C. In normal conditions, the temperatures here are normally 30-40°C lower, so this was a very significant warming event in progress.
As this was happening, the actual polar Vortex at this altitude (30km/18.5miles), started to look more triangular rather than the usual circular shape. The image below illustrates vorticity or energy of the Polar Vortex. It can be clearly seen that it was being drained from energy by a strong (barely noticeable) force. Anticyclonic systemOver the North Pacific and East Asia, pressing against polar vortex.
The Sudden Stratospheric Warming Event was observed on January 5th. The winds around the polar circle shifted from westerly to mainly eastern winds. This means that the North Polar Stratosphere now has a dominant high-pressure system.
The warming wave has covered all of the North Pole, effectively splitting out the cold-core from the polar vortex.
One half of the split polar vortex moved over North America, while the other moved over Eurasia. This was at stratospheric elevation, so it had little impact on the surface weather. You will see that the domino effect was already in full swing. Higher pressure was already moving down to the lower levels.
Below you can see the NASA temperature analysis from the polar stratosphere. The obvious temperature spike at 10mb (30km), in January 2021 was caused by the SSW event. This is a strong warming event. Temperatures remained above normal through February.
The stratosphere and the stratosphere are connected. Winter weatherIt helps to have more specialized images. One that incorporates altitude and time is the best, as it can show the progress.
The image below shows the atmospheric pressure index. The image below shows an atmospheric pressure index. Negative values are for lower pressure (cold colours) while positive values are for higher pressure (warm colors). In early 2021 we can see the lower part of the atmosphere, from the ground to the middle stratosphere (30km/18.5miles).
In January, you can see strong positive values within the stratosphere. This is due to the pressure rise that occurred during the stratospheric warm event. Slowly, the high-pressure influence began to decrease over time and reached its lowest level by mid-to late January. This was a significant influence on the Februarior. Weather circulationEven though the peak of the warming was over.
A strong Arctic high-pressure system can severely disrupt the weather circulation, and can even unlock the Arctic. Cold airFrom the Arctic regions to the mid-latitudes. The image below shows the temperature anomalies at the surface in the January-February 2021 period.
Temperatures that were higher than normal were observed under high pressure in the polar regions. Siberia was exposed to very cold Arctic air. A large amount of cold air was also pushed out to western Canada and the south central United States, resulting the strong Texas February cold weather outbreak.
We also did a pressure analysis for the January-February 2021 period. It shows the sea-level pressure anomaly. It shows a strong high-pressure system over the North Pole. This dominant high-pressure system was created by the stratospheric heating event and the polar vortex collapsing, which altered the circulation and dispersed the colder air towards southern regions.
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A strong North Pacific ridge rises to the Arctic Circle, pushing the Jet stream and colder temperatures deeper across the United States.
Source: Severe Weather