A global perspective of the limits of prediction skill of NWP models has been published in Tellus A. 

It shows that the analysis uncertainties in a state-of-the-art NWP system are largest in the tropics and have biggest amplitudes at the large scales. The growth of forecast uncertainties (ensemble spread) takes place at all scales from the beginning of forecasts. The growth is nearly uniform in the zonal wavenumbers 1–5 and strongly scale-dependent in the larger wavenumbers.  The growth from initial uncertainties at large scales appears dominant over the impact of errors cascading up from small scales.  

Full paper is available at http://www.tandfonline.com/doi/full/10.1080/16000870.2017.1317573?scroll=top&needAccess=true