Propagating equatorial disturbances such as the Madden Julian Oscillation (MJO) and Convectively Coupled Equatorial waves (CCEW) are often seen as potentially useful for sub-seasonal predictions in the tropics and elsewhere via tropical-to-extratropical teleconnections. Quantifying this potential has been proven difficult in numerical weather prediction systems because tropical sub-seasonal variability tends to be poorly represented in such models. One possible exception is the European Centre for Medium-Range Weather Forecasts Integrated Forecast System (ECMWF), which has been recently shown to have much improved representation of sub-seasonal tropical variability. In this study, we use ECMWF reforecasts to investigate the predicted evolution of CCEW and the MJO and how they might relate to sub-seasonal practical and potential forecast skill.  It is shown that systematic model errors in the representation of their amplitude and propagation characteristics strongly limits their role as a deterministic pathway to improve sub-seasonal predictions.