Warming this early on is an extremely rare event, have to go back to November 1968 for the last full blown November SSW whilst the last November Canadian Warming was 2000.
A few days ago, models including the ECM and GFS were pointing towards a bit of warming in the stratosphere which would certainly help from the point where we are right now which is record breaking cold levels.
Here are the latest stratosphere temperature analysis charts for 10hPa and 30hPa. You can still clearly see that the temperatures are well below average in the stratosphere.
This is the latest ensemble prediction chart from the GFS and CFS ensembles. The green lines (the GFS ensembles) forecast a dip in the zonal wind speeds at 10hPa in the next week which usually would correlate with a slight risk of weak blocking around the North Pole - this is what is indeed happening. However, after this dip, they forecast the zonal wind speeds to go back to average with a good few of them even going back above average. This would be associated with a stronger westerly flow and the chance of some late Autumn windstorms if it were to verify.
Meanwhile, the CFS ensembles continue to reflect weak zonal wind speeds through the early Winter and in this particular run of them, two ensembles take the zonal winds to reversed levels at the start of December. This would be a SSW event. Most ensembles continue the same theme through January before February shows a recovery especially with one particular ensemble member which goes to very strong zonal wind speeds. Obviously still all speculation and little to no reliability but it's always interesting to see nonetheless.
Why are we seeing this slight drop in the zonal winds? At 1hPa, there is a warming taking place which is at the very top end of the stratosphere. You can see this on the cross-section. To get a SSW, you'd want to see these warm temperature anomalies filter down into lower levels of the strat including 10hPa and 30hPa. This will not happen this time and we'll see a recovery in the Polar Vortex regaining strength (as shown from the above diagram and another below).
So, all in all, quite a healthy Polar Vortex for now with westerly patterns likely to dominate for the foreseeable future. The stratosphere is coupling up with the troposphere after a recent disconnection.
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