Polar Vortex Blog

Because this is the Polar Vortex Blog, we would love to be able to tell you how the stratospheric polar vortex is doing super cool things that can explain how cold and snowy it’s been in many parts of the US this winter. But the truth is, in our opinion at least, while the stratosphere has been doing some interesting stretching and wobbling, there’s just not much evidence that this is really the main driver of our winter weather so far this year. Little typical communication between the stratosphere and troposphere As we have described before, one measure of “typical” downward coupling between the stratosphere and the troposphere are these plots showing the difference from average …   Read article

The phrase “polar vortex” is often associated with words and phrases like “cold”, “sweater”, and “please, please, please don’t let my furnace break down now.” The disruption and weakening of the polar vortex winds do increase the odds of a cold air outbreak across the eastern US and northern Europe/Asia (but they don’t guarantee it). However, the polar vortex is a multi-faceted phenomenon. Read on to learn about the less-hyped side of the polar vortex. There’s more to the polar vortex than just disruptions We spent much of last season talking about the repeated disruptions in the polar vortex. This is when the stratospheric winds at 60 degrees North weaken substantially (or reverse di…   Read article

We’re briefly popping in because another surge of very cold air looks to drop down from the Arctic over a large region of the central US this weekend and into early next week. We know that the question will be asked: is the cold related to the polar vortex this time? So here we are to provide some answers. There are two points we want to emphasize: 1. The polar vortex strength, as measured by the speed of the winds around the 60N latitude circle and 10 hPa pressure level, remains stronger than average, and is currently forecast by most models to return to near-record strong wind speeds into early February. Normally, if the polar vortex is communicating with the surface, which it…   Read article

Parts of the Midwest and East Coast have been blanketed by the first major snow of 2025, with temperatures dropping as fast as my New Year’s resolutions. Do we have the stratosphere, the polar vortex in particular [footnote #1],  to blame (or thank) for this recent cold air outbreak? We don’t think so. This seems like a case of the polar vortex getting blamed for being a trouble maker, when it was actually minding its own business. We’ll tell you why below. Our usual suspect has an alibi: the polar vortex has been strong  A common way in which the stratospheric polar vortex contributes to  cold air outbreaks over the eastern U.S. usually involves two key ingredients.…   Read article

When we launched this blog last winter, the atmosphere came through for us with not one, but two breakdowns of the stratospheric polar vortex. That was very considerate of it, given that many winters pass without even a single one. With all the excitement that occurs when the stratospheric polar vortex is disrupted during a sudden stratospheric warming, our readers might wonder whether there is any way to predict weeks or even months ahead of time the likelihood that one (or more!) will occur this upcoming winter. As we discussed last year, there are certain ingredients that need to come together to drive a sudden stratospheric warming. These can be boiled down to two main factors:  …   Read article