My first interaction with A. Wiin Nielsen come through a note that he, while General Secretary of WMO, wrote in Tellus about a paper of mine: Benzi et al. (1982). He wrote: “ The model is therefore unsatisfying even as a simple climate model from a physical point of view.” To say the least, the opinion expressed in such a plain language hardly would be a good omen for the start of a conversation of any kind let alone of a friendship. Things radically changed in 1983 when we shared a period of visit at ECMWF. At that time, I was interested in estimating of the surface temperature inter-annual variance, a parameter that, in my view, would render more satisfying the model mentioned above at least from a physical point of view. I had noticed that in the Northern hemisphere winter the temperature distribution was not Gaussian at all especially at large scale. Discussing these matters with Wiin Nielsen, he presented me with a paper: Wiin Nielsen et al. (1964). The structure of the covariance fields there presented convinced both of us that the blocking events of 1963 may be distinguished from other type of flows for the anomalous behavior of a few gravest zonal waves, and in particular zonal waves centered on wave number 3. The present paper wish to further discuss this issue by using ERA40 reanalysis and the associated 10 days forecast. It will be shown that there is a considerably systematic error in the forecasts that can be related to the onset, duration and decay of blocking events, especially when these flow have global nature. I hope, needless to say, that Wiin Nielsen will look this time to my effort less critically than he did in the other occasion.