I googled QBO while trying to understand what WebHubTel is doing and found this: [Predictability of the quasi-biennial oscillation and its northern winter teleconnection on seasonal to decadal timescales](http://onlinelibrary.wiley.com/doi/10.1002/2013GL059160/full), Scaife et al

They say

> The skill of these QBO predictions remains high at very long lead times and is higher than other highly predictable modes of climate variability such as El Niño–Southern Oscillation [Fedorov et al., 2003; Barnston et al., 2012]. Correlation scores exceed 0.8 at prediction times up to 6 months. At 12 months lead time the correlations are still above 0.7, and positive correlations are maintained out to years ahead in both forecast systems (Figure 2), remaining significant out to 4 years ahead in the MiKlip forecasts [c.f. Pohlmann et al., 2013].

That's quite long but it's not very long. WebHubTel appears to be using a simple method to project the QBO back from 1953-2015 all the way to 1880. I cannot make sense of this.