An Overview of the Effects of the La Niña Climate Pattern and Polar Vortex on Record Breaking Winter Seasons Globally

Feeling the cool winds of winter? Surely, you are freezing or feeling a nip in the air. As one of the four Earth’s seasons, it goes after autumn and foreshadows spring is here so soon. Where did the whole of 2021 disappear too?

After the world is still reeling from the Covid-19 pandemic. We have something else to occupy our minds. Scientists predict that this winter will bring about the coldest winter season on record. I know what you are thinking about why there is such a fuss, as being cold in winter is normal. Even though cold winds and below-average temperatures are normally a part of winter. But this winter is set to be the coldest of the whole year. But not all the people in the tropical zones will not have to freeze. Trying to take in the magic of winter in the air, the frosty layer of ice, crystal clear glittering nights with twinkling stars. The star of winter is snow and just this amazing atmosphere.

This time of the year is ideal for indulging your adventurous side. Especially through snowboarding, ski riding, ice skating, snowball fighting, and much more. Winter is a time to be at home, drink hot tea or coffee, spend time with family, friends, watch movies and just savor every day!

But on the scientific side of things, the La Nina climate pattern ( a natural cycle marked by cooler-than-average ocean water in the central Pacific Ocean ) is one of the main drivers of weather all around the world. That is not all. The polar vortex impacts world weather as well. From the North Pole, South Pole, Antarctica, and US, Europe, and even India are experiencing record-breaking temperatures.

The La Nina Climate Pattern

This Climate.gov graphic shows how La Niña generally affects weather conditions in the United States. Forecasters say there's a nearly 90% chance that La Niña conditions will be in place from December 2021 to February 2022.
This Climate.gov graphic shows how La Niña generally affects weather conditions in the United States. Forecasters say there’s a nearly 90% chance that La Niña conditions will be in place from December 2021 to February 2022/ Photo: Climate.gov

“For the upcoming winter season, which extends from December 2021 through February 2022, there is an 87 percent chance of La Niña,”

– US-based National Oceanic and Atmospheric Administration had said in October.

The natural cycle of La Niña is set to continue as the Northern Hemisphere heads into winter. The weather forecasters are confident that it will hang around through the rest of the winter. This La Niña, the second in two years, will likely transition. There’s about a 60% chance the late spring and summer will feature neutral conditions. So, that’s some relief for people who aren’t a fan of the chilly winter winds.

For the second year in a row, the cooler sister El Niño showed up at the winter party in the Eastern Pacific. As this is the case with cool guests, La Niña is expected to stick around until at least spring 2022 in the Northern Hemisphere. Typical behavior overstaying your welcome on Earth.

The La Nina Intensification

As a part of the El Niño-Southern Oscillation cycle, La Niña appears when energized easterly trade winds intensify. Along with the upwelling of cooler water from the depths of the eastern tropical Pacific. This caused a large-scale cooling of the eastern and central Pacific ocean surface near the Equator. These stronger than usual trade winds also push the warm equatorial surface waters westward. Specifically towards Asia and Australia. This dramatic cooling of the ocean’s surface layers then affects the atmosphere by modifying the moisture content across the Pacific. The La Niña coupling of the atmosphere and ocean alters global atmospheric circulation.  Moreover, this causes shifts in the path of mid-latitude jet streams in ways that intensify rainfall in some regions and bring drought to others.

Effects of La Nina on the United States and Canada

Ice and snow cover branches near the brink of Niagara Falls
Ice and snow cover branches near the brink of Niagara Falls/ Photo: Reuters

The circulation of a strong high-pressure system promotes the development of a low-pressure region. Specifically in Alaska and western Canada. It curves the jet stream downwards in-between the two pressure systems.

The average position of the jet stream during La Nina winters causes the resulting weather patterns over the United States and Canada. Moreover, the shifting jet stream brings colder temperatures and storms down from the north. Consequently, the jet stream causes changes in northern and the northwestern United States. As well as the warmer and drier weather in the southern parts.

This way, the changing jet stream over the United States can divide the country into two weather poles.

In the northern part of the country, we can see that the colder and wetter events are more frequent, as the jet stream directions the storm systems that way. But that can somewhat lock up the southern United States, creating warmer and more stable weather with less frequent storms and cold fronts.

Precipitation and Snowfall Predictions in the United States and Canada

Looking at the precipitation pattern, we can see more precipitation in the northern half of the United States. That is where most of the cold fronts and storm systems travel during a La Nina winter. In contrast, drier conditions prevail in the southern and southeastern states. Of course, this doesn’t mean that a cold front can reach down into Texas, for example, if a break in the weather pattern permits it.

Shifting the jet stream also means changing the snowfall potential. As the colder air is more easily accessible to the northern United States, that also increases the snowfall potential if there is moisture available. In particular, areas like Alaska, Canada, and the northwest and the northern United States benefit from the jet stream to produce more snowfall.

After passing Canada and the United States, the jet stream moves out into the North Atlantic. There are different paths it can take from there. A lot depends on the overall circulation pattern and the existing pressure systems in the Atlantic. This is where La Nina perhaps loses its direct influence over Europe, as regional weather systems in the Atlantic play a role.

But it usually still has an important influence, as it changes the position of the entering jet stream from the west. The incoming jet stream can merge with the systems in the Atlantic, helping to create a whole new weather pattern for Europe. The problem is that the outcome is far more unpredictable in this region compared to North America, which feels a much more direct weather influence.

Impact of La Nina on Indian Weather

A view of Jammu and Kashmir's Gulmarg during heavy snowfall on Dec 10, 2018. (IANS)
A view of Jammu and Kashmir’s Gulmarg during heavy snowfall on Dec 10, 2018. (IANS)

The evolving winter conditions during the fall of this year are wielding the threat of harsher than normal winter. Similar La Nina conditions last year, albeit a bit stronger, spoiled the snowy season for the hilly states and corrupted the winter rains in the plains of northern India.

The rainfall deficiency during the winter season, in the states of Punjab and Uttar Pradesh is more than 70 percent. The hilly regions of Jammu and Kashmir and Ladakh, Himachal Pradesh, and Uttarakhand witnessed a ‘failed’ snowy season and experienced a shortfall of more than 50 percent. The National Capital observed a record number of seven cold wave days in January 2021, the maximum since 2008. This figure was just one day in January 2019 and 2020.

Double Dip La Nina

La Nina is expected to carry on with an 85 percent chance from December 2021-February 2022. It also means that the cooling of the first-year La Nina event of 2020 continues to evolve and may last till early spring of 2022. The continuation of La Nina conditions spanning over two consecutive years is also called ‘Double Dip’ La Nina. While it is uncommon to witness two El Nino events following each other, back-to-back La Nina episodes are not unusual. Statistically, of the 12 first-year La Nina events, six are followed by La Nina the next winter, four by neutral conditions and two by El Nino.

La Nina is getting colder than expected in the Equatorial Pacific Ocean. La Nina can be viewed as a big influencer of weather conditions during the fall of the year and it could keep responding adversely till early spring. It transports cold air over the Indian subcontinent from Siberia and South China. Occasionally, this cold air may interact with a north-south axis of the deep trough to extend much further south into parts of Maharashtra, Karnataka, Telangana, and Andhra Pradesh.

La Nina episodes in the winter months feature a wave-like jet stream. Specifically, flowing across Iran, Afghanistan, and the Hindu Kush mountains. The westerly jet stream, a channel of very strong and cold winds circumnavigating the globe. Consequently, this remains a dominant feature impacting the degree of cold over the Indian region.

The Polar Vortex

The science behind the Polar Vortex NOAA
The science behind the Polar Vortex/ Photo: NOAA

A new stratospheric Polar Vortex has now emerged over the North Pole. A La Nina copycat has decided to continue to gain strength well into the winter season of 2021/2022. It will interact with a strong easterly wind anomaly high over the tropics. This interaction happens every few years. Moreover, it has brought colder winters to Europe and the United States in the past.

What is the Polar Vortex?

In essence, the polar vortex is like a large cyclone that forms when the stratosphere over the North Pole starts to cool down.

When you hear people talk about the polar vortex and its influence, 90% of the time they talk about the higher altitude stratospheric part. While the stratospheric polar vortex is spinning high above our weather ( though strongly connected). It plays a major role in developing winter weather patterns across the entire Northern Hemisphere.

Every year as we head into autumn, the north pole starts to cool down. But the atmosphere further south is still relatively warm. As it continues to receive energy from the sun. This temperature difference causes a pressure drop over the polar regions.

As the temperature and pressure drop over the pole.  Along with a temperature difference towards the south increases. Consequently, a large low-pressure (cyclonic) area will start to intensify across the Northern Hemisphere. The same process happens in the stratosphere. This creates a large anti-clockwise spinning system.

The Polar Vortex Predictions of North Pole Winter

There is a glimmer of positive news as the polar vortex that contains icy air above the North Pole appears weaker than last year. That means there’s a greater chance that frigid cold will occasionally spill out of the Arctic into the temperate zones of Asia, North America, and Europe, bringing intermittent chilling effects throughout the season. So, the winter will be experienced in increments for a prolonged period.
Tilted away from the sun’s warmth for months on end, the North Pole builds a reservoir of some of the Earth’s coldest air during winter. A girdle of wind called the polar vortex spins around the top of the world, locking that cold air uptight. If it escapes the confines of the Arctic, parts of Asia, Europe, and North America will be blasted with bursts of cold, driving demand for heat.

Impact of The Polar Vortex on World Weather Patterns

Currently, the temperature is already dropping in the stratosphere. The temperature difference is forecast for the next two weeks, in the middle stratosphere. There is large-scale cooling over the majority of the North Pole. Looking at the current temperature forecast, we can see a nice cold-core starting to develop over the Polar Circle. This is the heart of the Polar Vortex. As the colder it gets, the stronger the polar vortex can become. That is because it feeds off the temperature/pressure difference between the polar and the southern regions of the Northern Hemisphere.

The pressure is also starting to drop rapidly. A smaller low-pressure area is starting to develop over the Arctic Circle. That is the foundation for the polar vortex of the upcoming winter 2021/2022. Towards late September, shown in the forecast, we can see the polar vortex is much more developed, and rapidly increasing in size and influence. As the pressure drops in the polar vortex, this increases its wind speed. The stronger it gets, the easier it is to influence our weather down at the surface.

Speaking of wind, the current forecast shows the stratospheric jet stream developing. It is also called the Polar Night Jet.

Current forecasts, when compared to the long-term average, show that the late September strength of the polar vortex is likely to be higher than usual.

Conclusion

The first day of winter in the Northern Hemisphere is marked by the winter solstice, which occurs on Tuesday, December 21, 2021, at 10:59 A.M. Eastern Standard Time. 

For the northern half of Earth (the Northern Hemisphere), the winter solstice occurs annually on December 21 or 22. (For the Southern Hemisphere, the winter solstice occurs on June 20 or 21.) The winter solstice is the day with the fewest hours of sunlight in the whole year, making it the “shortest day” of the year. Thankfully, after we reach the winter solstice, the days begin to once again grow longer and longer until we reach the summer solstice—the first day of summer and the longest day of the year.

Think of it this way: Although the winter solstice means the start of winter, it also means the return of more sunlight. It only gets brighter from here!

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