https://www.aer.com/science-research/climate-weather/arctic-oscillation/Dr Judah Cohen just posted to his blog, week 2 of talking about this stratospheric polar vortex disruption, click on Archives to see previous entries.
How I see it
Strat PV disturbances usually come in 2 main types, the displacement and the split. Split stratospheric PV usually leads to a total collapse of the vortex. The strat PV spins right back up into a vortex again, unless it is the final warming of the winter pole, but at some point the vortex feature loses all power when there's a good split. These type of SSW give us our best chance of prolonged cold winters in the US East, for example. People are looking for Wave 2 split events so they get snow. So far we have seen more Wave 1.
There's a regularity to these events, a climatology of them, winds and heat & momentum fluxes, as well as a profile of the temperature changes throughout the polar atmosphere. However, as with anything dynamic, it is hard to define the phenomenon. 10hPa zonal wind reversal at a high latitude is one example of a definition, or a way to locate the events in the archives. This vortex disturbance has already achieved Major Midwinter Warming and negative zonal winds at 10hPa.
Funny thing is, the warming part: It has been very loudly anomalous that we see so far 2 SSW status warmings at 10hPa with a third in the forecast.
The vortex feature itself is there. It splits at lower levels but cannot unzip totally. Pictured below is the 2nd "split." Some symmetrical splitting has occurred, but instead of separating into two cores, there's an accelerated merge. You get what looks like PV pants.
If you page through the isentropic PV and other maps on
https://stratobserve.com/tht_pvstr_maps you can go back to January 9th currently and look at hour 0s. I believe the 1st MMW was the 4th or 5th of January, 2nd about 10 days later, and the 3rd we're looking at hour 300ish from now.
Each time the vortex is displaced and sheeted flat, even splitting/merging and shedding smaller vortices at different levels. It is creating a challenge for the definition of these meteorological events, in one respect, because the vortex gets strained into such a sheeted flat feature that zonal winds are negative at 10hPa 60N, without that spectacular loss of power that people are hoping for so they get snow.
Regular SSW are normal and kind of like playing Roulette for weenies during winter, they are semi-regular but with a hiatus in the 90's. A good SSW can fill in ozone over the poles.
Too strong vortex destroys ozone at the poles.
4 posts above is a relevant post from me, about Stratospheric Final Warmings being modeled occurring later by a few days in some WACCM-X style models.
Winter vortex were too strong at lower stratospheric levels late in the past 2 cold seasons, which is how I interpret those two charts
https://stratobserve.com/misc_vort3dhttps://www.cpc.ncep.noaa.gov/products/stratosphere/There is a lot going on in the stratosphere and the race is on to figure it out.