The same comparisons presented in this section were also performed with the ECMWF operational model, pro-vided at 0.25◦ x 0.25◦ spatial resolution and at the same 6-h intervals. The results are very similar to those shown in Fig. 3. The main difference is that the residuals with respect to the ECMWF operational model become slightly larger as we go back in time. This is in agreement with the fact that the ECMWF operational model has been suffering several improvements, being at present, very similar to ERA Interim. In fact, considering the lowest spatial resolution of ERA Interim when compared with the ECMWF operational model, its performance is remarkably good, since the present results suggest that, when considering the latest years, their performance is very similar.