Stratosphere Hinting at Long Range Cold Snap

The stratosphere is telling us that the Central and East US may be in line for some very cold weather in the second half of December, and verification from its last cold weather indication says that we should be monitoring this development.

Between October 30 and the first few days of November, the Central and East US experienced above normal temperatures in the upper stratosphere. This is displayed well in the Climate Prediction Center's reanalysis of the 30th in the image above. These few days between the end of October and the start of November also included slightly above normal stratospheric temperatures diving south from Canada, with below normal temperatures observed in the Pacific Northwest. Because the effects of stratospheric warmings are typically seen 2-4 weeks after the warming event, we took a look at surface temperatures from November 14-28 to see how well the surface temperatures matched up with the upper stratospheric temperature anomalies (note that this is a negative correlation relationship, meaning above-normal stratospheric temperatures will lead to cold surface temperatures, and vice versa).

Ground-level temperature verification from November 14th to November 28th, approximately 2-4 weeks after the height of this US upper stratospheric warming event, is nearly identical to the temperature anomalies experienced in the stratosphere. The regions that saw above normal stratospheric temperatures, including the Central and East US, as well as Canada, saw below normal temperatures during this timeframe. Similarly, the Pacific Northwest, which was bathed in slightly below normal upper stratospheric temperatures to kick off November, was included in slightly above normal surface temperatures from November 14th to November 28th. It would seem to me that the stratosphere had a direct involvement with these surface temperature anomalies, given how well the stratospheric and surface temperature anomalies line up.

In the last few days, the upper stratosphere has suddenly sprang to life, with a wide swath of much above-normal temperature anomalies extending from as far west as the Rockies to the Eastern Seaboard, through the Atlantic Ocean and off to far western Europe. This would seem to hint at colder than normal weather making a return to the nation somewhere in the December 14-28 timeframe, roughly 2-4 weeks after yesterday (November 30th). Normally, I wouldn't be putting so much faith in the stratosphere to dictate temperatures for the next few weeks. However, with its stellar verification in the prior event, I'm willing to give this stronger warming event a shot. That said, I'm going along with this colder than normal prognosis for December 14-28 with low confidence, as there are a few other factors that may try and intervene to bring about warmer temperatures for this timeframe than what the stratosphere is suggesting. But until those come to fruition, I'll go ahead with the stratosphere's call for cooler temperatures between December 14th and 28th.

Andrew