Sudden Stratospheric Warming Begins
By Andrew at 3:17 PM

As expected, the sudden stratospheric warming has begun over Canada as of the day after Christmas. This sudden warming is signified by massive warm temperature anomalies flooding into the Arctic.

In these sudden stratospheric warmings (SSW), warm air penetrates the stratosphere and is forced up high into the stratosphere. When the warm air is forced up, cold air originally from the stratosphere is forced down to the surface. There is a couple week lag between sudden stratospheric warmings and cold air reaching the surface. I'm not confident of the exact number of days it takes for this cold to hit the surface, but I think we should see this SSW's effects by mid to late January, something that could bring downright frigid air to much of the nation IF the atmospheric pattern cooperates.

It should be mentioned that SSW's cause trough formation later on. Like we saw with the Dec. 1-6 SSW in the first several frames of the animation above, we are now seeing forecasts of low pressure building in the Bering Sea, right where that first SSW occurred. If the same rule applies, the end of January could see anomalous low pressure building over Canada, possibly extending into Greenland- something that could ignite the infamous, anti-cold-and-snow positive NAO. But that's a different post for a different time.

Andrew [link to theweathercentre.blogspot.de]