The mean over the latitude band at each longitude, through time: oldest at the top. Above the line,
ECMWF's analysis (the T+0 of its deterministic run) at 00Z and 12Z; below it, the chosen run's ensemble mean every
6 hours. The archive keeps 60 days. In bias mode each row is one forecast minus the analysis
at the time it was for, and the chart beneath gives the mean error, the RMS error and the spread at each longitude.