Stratospheric Warming Event Commences

A temperature animation of the upper stratosphere shows that East Asia is now experiencing a stratospheric warming event, something that could be a sign of things to come this winter.

As the animation shows, the last few days have seen a big jump in stratospheric temperatures in Eurasia as a result of a persistent rise in mountain torque values. Without going too in-depth, high values of mountain torque in certain regions of the world (in this case, East Asia) can lead to sudden stratospheric warming (SSW) events. This is the first such warming event this winter, and one can only question if this is a sign of things to come.

Observed mountain torque values (Note the elevated East Asian mountain torque values in red on the right side of the graph).

This warming event could help to weaken the polar vortex in the short and medium term, despite projections for the polar vortex to strengthen in the next several days. Implications on the winter could range from nothing to this warming event being a big blow to the polar vortex this winter. My money's on this warming event having little effect on the winter's polar vortex, especially because we are still in a positive Quasi-Biennial Oscillation (QBO) phase, which favors a stronger polar vortex. However, a stratospheric warming event in January or February would have a very different impact on the winter, and this is something I will address in my Final 2013-2014 Winter Forecast, which comes out this Thursday at 5:00 PM Central Time.

Andrew