New Polar Vortex Blog

[morganism]

Welcome to the Polar Vortex Blog!

We are excited to announce that NOAA Climate.gov, home of the highly popular ENSO Blog, is venturing into a colder, darker, and windier corner of the atmosphere with the new Polar Vortex Blog. We plan to explore various facets of the winds, climate, and chemistry within the fascinating region of the atmosphere known as the polar stratosphere, and explain how this region can sometimes drive big changes in our weather patterns!

While ENSO may be the seasoned celebrity in the seasonal forecasting world, in recent years the stratospheric polar vortex has become a rising star: constantly making headlines and being stalked by the paparazzi, but often misunderstood or misrepresented. We hope to clear up misconceptions, highlight new research, and discuss what the polar vortex is up to and how it may affect our winter’s weather. We expect there to be 1-2 posts per month between December and March, with the initial focus on the Northern Hemisphere polar vortex (yep, there’s one down south, too!).

https://www.climate.gov/news-features/blogs/polar-vortex/welcome-polar-vortex-blog


along with supporting actor

https://stratobserve.com/misc_vort3d

[morganism]

new post up

https://www.climate.gov/news-features/blogs/polar-vortex/cooking-stratospheric-polar-vortex-disruption

[kassy]

Nice discussion on SSWs and also what we still have to figure out.

[vox_mundi]

The Polar Vortex Is Spinning Backwards
https://www.climate.gov/news-features/blogs/polar-vortex/welcome-polar-vortex-blog

Earlier this month, atmospheric scientists noticed something unusual in the Arctic stratosphere. The polar vortex was spinning backward.

"The vortex changed direction around March 4th," reports Dr. Amy Butler, author of NOAA's Polar Vortex Blog. "It was a substantial reversal, reaching -20.5 m/s a few days ago, which puts it in the top 6 strongest such events since 1979."



Two weeks later, it is still spinning backwards. What's going on?

"Atmospheric planetary waves have been breaking in the polar stratosphere, increasing its temperature," says Butler. "We call this a 'Sudden Stratospheric Warming' event, and it can cause the vortex to change direction.'"

In recent years, many people have heard the phrase "polar vortex" because of the effect it can have on winter weather. When the polar vortex is strong and stable, it helps confine cold air to polar regions. When the vortex weakens or becomes disturbed, cold air spills out to lower latitudes.

This month's backward vortex has *not* caused an outbreak of winter weather. Instead, it has produced a very strong increase in polar ozone.



"Sudden Stratospheric Warming events accelerate the transport of ozone from the tropics to the poles," explains Butler. "Also, warming air helps prevent chemical ozone loss."

The current 'ozone spike' -- the opposite of an ozone hole -- is the biggest in the month of March since record-keeping began in 1979.

Soon, things could return to normal. The vortex's backward-spin is slowing, and "could become westerly again in about 10 days," says Butler. If so, the ozone spike will subside.

[morganism]

What does the South Pole Stratospheric Warming mean for Winter 2024/2025?

A strong Stratospheric Warming event is ongoing over the South Pole. It has disturbed the southern Polar Vortex and will help to create strong weather anomalies at the surface. But the latest forecast data suggests that its impact might be far more reaching, likely even into the Winter of 2024/2025, over the Northern Hemisphere.

We wrote about this event as it started, around mid-July. Since then, we have discovered a study that suggests a connection between the southern and northern hemispheres and these strong events.

The Southern Hemisphere does not experience a stratospheric warming event very often, with only a few known events in the past decades. But, as you will see, these events can have a far-reaching effect despite unfolding on the other side of the world.
(snip)
Below is the latest pressure anomaly in the stratosphere over the south pole. You can see the polar vortex is now being compressed by two high-pressure anomalies, not just one. These are strong high-pressure anomalies that are changing the very shape of the polar vortex.
The latest temperature anomaly analysis also shows a strong temperature anomaly at this level (10mb ~ 30km/18miles). You can see that the stratospheric warming wave has expanded and surrounded the polar vortex, raising temperatures much above the normal values.
(snip)

This graphic shows a signal that prolonged high-pressure anomalies over the South Pole in the August-October period can indicate low-pressure over the United States Midwest, the Northeast, and Southwest the following December-February. A high-pressure anomaly is indicated for Europe.

If we look at the actual ECMWF pressure forecast for the November-January period, we can see a very similar pattern. You can see a low-pressure area positioned over southern Greenland and into eastern Canada and the northern United States, and a high-pressure over Europe.
(snip)
But, there is a large caveat here: This correlation does not mean that the high-pressure anomaly over the South Pole is directly responsible for the lower temperature signal over the United States the following winter. It just indicates some connection but doesn’t explain what exactly it is.

As we know, a large-scale event like Stratospheric Warming can cause a prolonged high-pressure anomaly over the South Pole. With several weeks to months of time, some effects of the SSW event could perhaps manifest in the Northern Hemisphere through the large-scale atmospheric motion.

A study made in 2018 by a group of authors focused directly on the connection between the north and south hemisphere pressure anomalies. The study found conclusive results for events over one hemisphere affecting another, likely through the stratosphere and polar vortex dynamics.
(more)

https://www.severe-weather.eu/long-range-2/south-pole-stratospheric-warming-winter-2024-2025-influence-forecast-united-states-canada-europe-fa/

[kassy]

Something’s Going On With The Polar Vortex, And It Could Have Consequences

The southern polar vortex is currently showing rare signs of extreme instability, leading to fears that it could collapse, bringing both icy blasts and extreme heatwaves to the southern hemisphere. Likewise, the northern polar vortex had yet another wild winter this year, and with climate change set to intensify these perilous polar patterns, we could be in for some increasingly dramatic weather in the years to come.

The polar vortices are strong stratospheric air currents that circulate over the Arctic and Antarctic during the winter months, trapping cold air above the poles. They are surrounded and enclosed by the jet streams, which act like barriers that prevent this icy polar air from spreading into the mid-latitudes.

However, every now and then, the stratosphere above the Arctic experiences a dramatic increase in temperature and pressure, destabilizing the northern polar vortex and causing it to split, change direction or collapse. When this occurs, the jet stream tends to become warped, allowing icy Arctic winds to encroach further south than they usually would, while warm air is drawn into the polar region.

Known as sudden stratospheric warming (SSW), this phenomenon caused the big freeze that gripped parts of the US in 2019. In early 2024, fluctuations in stratospheric pressure caused the northern polar vortex to change direction twice, bringing cold snaps to the northern hemisphere, although neither event was strong enough to significantly alter the shape of the jet stream.

Down in Antarctica, however, SSWs are much less common, with the only known instance occurring in 2002. Yet that could be about to change, with a series of stratospheric temperature increases since last month raising fears that the southern polar vortex could be about to split.

The first of these was detected in mid-July, when wind speeds in the vortex slowed from their typical velocity of 300 kilometers per hour to just 230 kilometers per hour (186 to 143 miles per hour). This was accompanied by a temperature spike of about 20 degrees Celsius (36 Fahrenheit) above the average.

While these fluctuations were insufficient to trigger an SSW, they were followed by a second slowdown as temperatures rose once again in early August. This event has resulted in cold Antarctic air escaping from the polar region and blasting parts of Australia, New Zealand, and South America with wet and icy weather.

At the same time, warm air from the mid-latitudes has been able to push south into Antarctica, triggering a record-breaking heatwave.

It’s currently unclear how the situation will play out, with some predictions suggesting the southern polar vortex may soon stabilize, while other models hint at a drastic collapse. In the latter scenario, a destabilized jet stream will most likely disrupt another weather system called the southern annular mode, sending it into what’s known as a negative phase.

This would then result in an exceptionally dry and hot summer across Australasia and South America.

...

https://www.iflscience.com/somethings-going-on-with-the-polar-vortex-and-it-could-have-consequences-75509

[kassy]

Something’s Going On With The Polar Vortex, And It Could Have Consequences

The southern polar vortex is currently showing rare signs of extreme instability, leading to fears that it could collapse, bringing both icy blasts and extreme heatwaves to the southern hemisphere. Likewise, the northern polar vortex had yet another wild winter this year, and with climate change set to intensify these perilous polar patterns, we could be in for some increasingly dramatic weather in the years to come.

The polar vortices are strong stratospheric air currents that circulate over the Arctic and Antarctic during the winter months, trapping cold air above the poles. They are surrounded and enclosed by the jet streams, which act like barriers that prevent this icy polar air from spreading into the mid-latitudes.

However, every now and then, the stratosphere above the Arctic experiences a dramatic increase in temperature and pressure, destabilizing the northern polar vortex and causing it to split, change direction or collapse. When this occurs, the jet stream tends to become warped, allowing icy Arctic winds to encroach further south than they usually would, while warm air is drawn into the polar region.

Known as sudden stratospheric warming (SSW), this phenomenon caused the big freeze that gripped parts of the US in 2019. In early 2024, fluctuations in stratospheric pressure caused the northern polar vortex to change direction twice, bringing cold snaps to the northern hemisphere, although neither event was strong enough to significantly alter the shape of the jet stream.

Down in Antarctica, however, SSWs are much less common, with the only known instance occurring in 2002. Yet that could be about to change, with a series of stratospheric temperature increases since last month raising fears that the southern polar vortex could be about to split.

The first of these was detected in mid-July, when wind speeds in the vortex slowed from their typical velocity of 300 kilometers per hour to just 230 kilometers per hour (186 to 143 miles per hour). This was accompanied by a temperature spike of about 20 degrees Celsius (36 Fahrenheit) above the average.

While these fluctuations were insufficient to trigger an SSW, they were followed by a second slowdown as temperatures rose once again in early August. This event has resulted in cold Antarctic air escaping from the polar region and blasting parts of Australia, New Zealand, and South America with wet and icy weather.

At the same time, warm air from the mid-latitudes has been able to push south into Antarctica, triggering a record-breaking heatwave.

It’s currently unclear how the situation will play out, with some predictions suggesting the southern polar vortex may soon stabilize, while other models hint at a drastic collapse. In the latter scenario, a destabilized jet stream will most likely disrupt another weather system called the southern annular mode, sending it into what’s known as a negative phase.

This would then result in an exceptionally dry and hot summer across Australasia and South America.

...

https://www.iflscience.com/somethings-going-on-with-the-polar-vortex-and-it-could-have-consequences-75509

[gerontocrat]

Something’s Going On With The Polar Vortex, And It Could Have Consequences

Down in Antarctica, however, SSWs are much less common, with the only known instance occurring in 2002. Yet that could be about to change, with a series of stratospheric temperature increases since last month raising fears that the southern polar vortex could be about to split.

The first of these was detected in mid-July, when wind speeds in the vortex slowed from their typical velocity of 300 kilometers per hour to just 230 kilometers per hour (186 to 143 miles per hour). This was accompanied by a temperature spike of about 20 degrees Celsius (36 Fahrenheit) above the average.

While these fluctuations were insufficient to trigger an SSW,
It’s currently unclear how the situation will play out, with some predictions suggesting the southern polar vortex may soon stabilize, while other models hint at a drastic collapse. In the latter scenario, a destabilized jet stream will most likely disrupt another weather system called the southern annular mode, sending it into what’s known as a negative phase.

This would then result in an exceptionally dry and hot summer across Australasia and South America.

https://www.iflscience.com/somethings-going-on-with-the-polar-vortex-and-it-could-have-consequences-75509

As you can see from the ERA5  SATs graph daily SATs South of 66.5 are in record high territory.
The map shows that these high +ve te,perature anomalies are mainly on the Antarctic continent.

And you can see from the attached gif (click to start), cold is spreading even further North into the Weddell and Ross Seas and beyond.