High above the surface near the equator is a band of strong winds which alternate between westerly and easterly flow on a regular cycle. Surprisingly, the cycle is not tied to the calendar year but switches between phases in a 28-month period. I’ve put a graph of the oscillation, which is called the Quasi-Biennial Oscillation or QBO, below, or you can view it here. Wikipedia has a good article about it here. The phenomenon has been known since the 1950s, and has been tracked regularly since then, with only small cycle-to-cycle changes in the length of the reversal. Until this year.
In February scientists noticed that instead of going through its regular cycle from positive to negative phases, the QBO reversed its usual shift and went back to the old positive pattern (see the far right end of the graph in the red dots). Since this has not ever happened in the period from 1960 to now, the scientists don’t know what is causing it and what impact it will have on our weather. This is more of a concern now that the La Niña is less likely to occur, leaving other global influences to have more important effects on Southeastern weather.
The State Climate Office of North Carolina published a blog post in 2014 discussing the impacts of a negative QBO on NC climate and showed that for a negative phase, North Carolina was more likely to experience a wintry winter than other years. But since the QBO reverted to its positive phase, does this mean that the Southeast may have a lower chance of a cold winter? It’s probably too early to say, since we don’t know how long this strange situation will continue, but it will definitely bear watching.
You can read more about this at Gizmodo https://gizmodo.com/a-60-year-old-pattern-in-the-stratosphere-just-reversed-1786158830 and at Sciencemag.org here.
