- The wrinkle in the winter forecast could arrive as soon as early January.
- The polar vortex could become pinched and weakened.
- This could eventually lead to a cooler pattern developing over the eastern United States later in January or February.
- Regardless, both strong El Niño and blocking patterns could also contribute to an interesting winter.
The polar vortex may weaken in January, which could lead to colder weather in the United States from January to March.
Cold isn't a word we've used much this season. It is one of the warmest Decembers ever recorded in many northern locations in the United States, and the snow cover is still present At or near 20-year lows this time of year.
So, let's explain some of the possible changes ahead, including one mile above the Earth's surface.
What is a polar vortex? Nearly 10 years ago, the “polar vortex” entered popular culture during a cold outbreak in January 2014. This rotating cone of low pressure is located near the poles (hence “polar”) – the vortex – always in the colder months. But it is located high in the stratosphere, the layer of the atmosphere above which most of our weather occurs.
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The layers of Earth's atmosphere include the lower layer, the troposphere, where most weather occurs, and the stratosphere immediately above it, where the stratospheric polar vortex develops.
(NOAA)
Changes in the polar vortex: This whirling dervish high above the ground varies in strength and location in the colder months. Sometimes it is strong, perfectly circular, and directly above the pole. Other times, it weakens, expands, or even splits, with its center away from the pole.
When this happens, there is a sudden rise in the temperature of the stratosphere. Suddenly, we mean that temperatures in the stratosphere could rise dramatically by 50 to 70 degrees in just a few days.
This is exactly what many computer forecast models suggest could happen in early to mid-January.
So, if it's above our weather layer, why do we care? It may seem counterintuitive, but it turns out that after the polar vortex weakens, expands or splits, winter weather over Europe and North America can get colder and snowier for a while.
This can happen because warm stratospheric air can escape into the layer of the atmosphere where weather occurs.
This warm, falling air does not reach the ground, but remains in the upper levels, where it can create blocking patterns that help release cold air first into Europe, and then eventually into parts of the United States.
One such blocking pattern is known as the Greenland Block, which can transport cold air from Canada and the Arctic into the eastern half of the United States.
Typically, it takes at least a few weeks after a stratospheric warming event for any of its cooling effects to be felt.
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“Greenland block” pattern (or negative NAO phase).
Here are the warnings: Assuming this weakening of the polar vortex occurs as expected, and warmer air in the stratosphere creates obstructing patterns, this could indicate that we may see a cooler pattern in the United States later in January or February.
However, the Greenland block pattern does not require a weaker polar vortex. If this is set up early, the weather could get colder, regardless.
Then there is the current strong El Niño, which is also having an impact on the winter pattern. It is typically cooler and wetter from January through March in the South and parts of the mid-Atlantic states.
Deviation of temperatures from the average (in degrees F) in January, February, and March during the nine previous strong El Niños from 1958 through 2016.
(Noah Bessel, Ceres-CU)
The bottom line: Although there is uncertainty, the key takeaway is that for many, especially in the eastern half of the country, we could see a significant change in pattern including colder, and possibly snowier, conditions later in January or February. .
More at Weather.COM
– Dive deeper into the polar vortex
– How a stronger El Niño could affect snowfall this winter
– 5 ritual wishes that we hope will come true in 2024
– The 10 strangest things we saw in the weather of 2023
Jonathan Erdmann is a senior meteorologist for Weather.com and has been covering national and international weather since 1996. His lifelong love of meteorology began with a close encounter with a tornado as a child in Wisconsin. He studied physics at the University of Wisconsin-Madison, then completed a master's degree working with dual polarization radar and lightning data at Colorado State University. Extreme and strange weather are his favorite subjects. Contact him on X (formerly Twitter), Threads, Facebook And the sky is blue.
The Weather Company's primary journalistic mission is to report on breaking weather news, the environment, and the importance of science in our lives. This story does not necessarily represent the position of our parent company, IBM.
