Buckle Up: Stratospheric Warming Could Trigger Cold Outbreaks

Break out the longies.

Rumblings about some extreme cold outbreaks possible this winter.
If they occur, they will test electricity generators of all kinds, as well as the transmission grids that have been shaken in cold waves of recent years, but have been shored up recently, especially with new equipment and battery storage installations.

Arctic Oscillation and Polar Vortex Blog – Judah Cohen PhD, MIT:

Plain Language Summary

So far this fall it has been relatively mild across the Northern Hemisphere (NH) continents with the biggest exception of Siberia (see Figure). I do think that the fall temperature pattern across Eurasia has been supportive of a weaker polar vortex (PV) and is the focus of this week’s blog. The forecast does feature colder weather, mostly for Europe, Southeastern Europe and the Northeastern US this week and then Siberia and Western Canada next week (see Figures 3, 6). Eventually colder air spreads across much of Canada (see Figures 9). Longer term the weather will likely depend on the (almost) unprecedented disruption for late November. Potential is there for an interesting period of weather starting in December.

CNN:

High above the North Pole, in a slice of atmosphere rarely noticed and even less understood, a transformation is underway. Over the next 10 days, changes in the stratosphere will upend weather patterns and set the stage for a cold, snowy December across parts of the Northern Hemisphere.

It will mean a dramatic swing in weather for parts of the US that are currently simmering in record heat just a week before Thanksgiving.

It could also be one of the earliest significant polar vortex disruptionsrecorded since the dawn of the satellite era.

Think of the stratospheric polar vortex like a wall of wind, corralling the ultra-cold, Arctic air over the North Pole. When it weakens, cold air spills south into places like the Lower 48, Europe and Asia.

Right now, the air in the stratosphere — the layer of the atmosphere above where most weather occurs — is warming quickly and dramatically, in a phenomenon known as a sudden stratospheric warming event.

But the sudden warming in the far upper atmosphere is going to result in anything but warmth. It is causing the polar vortex winds to weaken, said Amy H. Butler, a meteorologist at the National Oceanic and Atmospheric Administration, and they could even reverse.

Scientists are still trying to figure out why these warming events happen, and for good reason: they can trigger the most intense “polar vortex” cold-air outbreaks in the US.

Over the next two weeks, these shifts could start to be felt in North America, Europe and Asia as the polar vortex weakens and tumbles south, like a spinning top that slows and wobbles off course.

—
I spoke to Judah Cohen, and then Nebraska State Climatologist Martha Shulski on this topic a few years ago.

Washington Post:

Sudden stratospheric warming events in November are uncommon, with only one occurring since the 1950s — and the one predicted this November may become the earliest on record.

They more typically occur in January and February and not in November or December. That’s because the polar vortex is still in its formative stages during late fall and early winter, making it less susceptible to warming events.

A major sudden stratospheric warming must include a rapid rise in stratospheric temperatures and sharp deceleration in winds. A minor warming event requires only a rapid rise in temperatures. These factors can disturb the polar vortex, with flow-on effects to weather patterns lower in the atmosphere.

“The reason we pay attention to sudden stratospheric warming events is not only because the weather impacts can occasionally be severe, but also because changes in the stratospheric winds can lead to persistent changes in weather for many weeks, giving us more time to prepare,” said Amy Butler, a research scientist at the National Oceanic and Atmospheric Administration’s Chemical Sciences Laboratory.