Eric Webb says:

First want to say Levi, I have been watching your videos for years and I have learned so much from you, and you do a fantastic job, and hope to see more videos soon. I do have a concern I want to address to you regarding something I have been taking note of in regards to the stratospheric warming event and the cold over northwestern North America, which could lead to some forecasting headaches, and I want to get your take on this.
Here’s what I said on another blog on this issue

“After reading Joe D’Aleo’s post and looking at the stratosphere, my concern is growing for a significant stratospheric warming event later in the winter. Joe D’Aleo makes a good point about how the warming is coming up from the surface, which I find interesting, because would make sense given how cold the surface temperatures compared have been in the higher latitudes for the last several weeks, the air pressures would likely be rising near the surface due to cold air’s natural property to sink. Over time as more cold air builds up, the pressures rise further, and this naturally would force the air pressures above this general layer in the atmosphere to drop in response to that, and with a drop in air pressure, the air molecules will have a tendency to move more freely about, thus the expanding the layer of air. Like a disease, this cold air spreads even further, the effects of the expanding atmospheric layer forces its way upward and into the stratosphere, which is what we seem to be seeing at this point in time. The 100 millibar charts that Joe D’Aleo put out showed the warmth at that layer in the atmosphere, and looking at the 10 millibar level, I don’t see anything yet, but the GFS model begins to hint at some more significant warming taking place in a little over a week from now. I think that it will take more time, probably on the order of at least 2-3 weeks before the 10 millibar level begins to warm substantially, given the lower concentration of air molecules at this level, thus, a longer response to the same changes being currently experienced in the troposphere and lower stratosphere is likely to occur. With the temperatures already warm below the stratosphere, this makes a stratospheric warming event all the more likely.

With the pattern at the 500 millibar level being eerily similar to 2010-11 with two dominant blocks of high pressure over the higher latitudes, (both current highs being in almost the exact same positions as in that year as well).], I’m inclined to think, just like Joe Bastardi, that much of the US will experience a white christmas this year. The one major difference is that the water temperatures surrounding Greenland are not as warm as they were in 2010-11, which would imply to me that the AO & NAO, although it should go negative, probably not to the degree of that winter.

This is the concern I have in this instance, as we have seen for the past few months, even with some decent blocking and large troughs into the US, the “motherload of arctic air” over Alaska and NW Canada has stayed intact, and even intensified further. I think that if we don not see the NAO and AO tank deeply into the negative within the next month or so, I think the only way this cold airmass is ever going to come down and deplete that area of cold air is through a major stratospheric warming event. Also considering how last year was predominantly positive and a decent amount of cold air over the arctic remained relatively untouched last winter, makes me even more concerned that the majority cold air will likely have to be forced out by some kind of significant event, and these hand-off scenarios and decently strong troughs into the US probably are not going to cut it, most likely a stratospheric warming event will be necessary to deplete the cold air sitting over NW Canada and Alaska. We all know how these events can turn out, 1985 is a good example of how cold it can really get. (although a little bit on the extreme side of things for now)”

Eric Webb says:

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/gif_files/gfs_t100_nh_f00.gif
There are clear signs of warming here, aligned directly near the Rossby wave that has persisted over the Pacific for the last several weeks with a trough near western North America and blocking over the North Pacific. This warming though is unusual, and appears to be originating from the surface, unlike what usually occurs, where the warming tries to work its way down to the troposphere, and this probably due to the abnormally strong amount of cold air that has been residing near Alaska and NW Canada. Theoretically, this cold air would naturally be forcing pressure rises near the surface due to colder air’s naturally property to sink and take up less space than warm air, and at the same time this allows for the layers above to expand and warm, and over longer periods of time, this is able to work its way up through the troposphere and into the stratosphere. Although in this instance, the warming is not too terribly significant above 100 millibars.
The vortex itself appears to become somewhat misaligned at different levels of the atmosphere as time progresses, and like any region of low pressure, centers need to be vertically stacked throughout the atmospheric column for significant strengthening to occur. Along with some warming evident in the lower stratosphere, this reveals that the vortex is in a weakened state, especially in comparison to last year.
http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwf1f240.gif http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwf10f240.gif http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwf100f240.gif