Notes on the upcoming stratospheric warming

   Posted by Levi at 11:46pm on January 5, 2012

The above video explores stratospheric warming events that have occurred since 1979 during El Nino and La Nina winters. We are likely facing a stratospheric warming event forecasted to develop during the rest of January, and it is already being proclaimed as the kick to the bucket that will allow cold to pour into the eastern United States. While the pattern may turn colder overall for the U.S., the video shows how many strato-warming events never shove cold all the way into the eastern U.S. during La Ninas. The reason is that the stratosphere’s influence over the troposphere is not all-powerful, and is often overcome by other things happening within the troposphere itself, such as the PDO and ENSO signals which, when negative, often keep the southeast U.S. ridge intact, allowing warmth to remain. During El Nino winters, however, the Pacific pattern is aligned with what the stratospheric warming tries to do, and all of those events are very cold for the eastern United States.

It is not clear yet whether this upcoming warming event will work its way down to the troposphere and provide arctic blocking, but some models are supporting that idea along with a colder pattern for North America. If this happens, I have a feeling that the models will again overestimate the cold for the rest of the winter in the eastern U.S., and while a battleground may set up between warmth in the southeast and cold trying to invade the midwest and New England, overall the eastern seaboard will remain near normal to slightly above normal, rounding out the rest of the winter. Transient cold shots may still occur, such as the big one that just roared through the east during the last couple of days, bringing freezes to Florida. However, despite the potential development of arctic blocking, there may be more inviting places for the cold air to go than into the eastern United States, though overall the pattern will likely turn colder for the country as a whole.

We shall see what happens!

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