What is it?
The QBO measures equitorial zonal winds that fluctuate between westerly (positive) and easterly (negative). These winds are measure in the tropical stratosphere which impact the tropospheric circulation. In turn, the QBO can impact the Northern Hemisphere pattern via subsequent interruptions in the polar vortex and stratosphere.
More information can be found via the link below provide by the Free University of Berlin’s atmospheric sciences division: here
Current QBO Data
It is important to note that positive numbers suggest westerly winds and a westerly QBO and negative numbers are indicative of easterly winds and a negative QBO. The QBO is highly cyclical and therefore more predictable than some other indices.
Source: New England NAO