Using ECMWF's Forecasts (UEF2019)

Typical map based ensemble visualisations have various shortcomings. Plotting the ensemble members in separate small postage stamp maps reveals all the information about the parameters shown, but it is difficult to compare the locations of weather phenomena between the maps. Probability plots make it easy to see how many ensemble members predict a phenomenon at any map location, but require choosing a single threshold, such as temperature below zero. Choosing a threshold discards information about all the other possible values a parameter may have. It also requires mental effort to think about weather in terms of probabilities, rather than in the familiar terms of weather parameters such as temperature or precipitation. We present a map visualisation, which can show multiple values of a parameter from all the ensemble members at the same time, and in addition manages to be highly intuitive. The visualisation is especially powerful when animated as a function of time and beautifully reveals the evolving uncertainties in the prediction.