The upper tercile corresponds to the third of years with the highest variable values and the lower tercile corresponds to the third of years with the lowest values. Note that the colour scale for precipitation has been reversed.
The median value of the variable observed in the past.
This chart shows the prediction from the ECMWF prediction system for the next season. Overall, different simulations are run, resulting in a range of potential outcomes.
The upper tercile gives the predicted probability for the variable to have higher than normal values in the next season, the mid tercile gives the probability to have normal values, and the lower tercile the probability to have lower than normal values. Note that the colour scale for precipitation has been reversed.