[en] In case of nuclear power plant failure or any other accident that would produce the dispersion of volatile radioactive material in the atmosphere, the first and immediate concern relates to where the material is going to be transported by the atmospheric flow and deposited at the ground. Forecasting the dispersion of radioactive material in the atmosphere is normally demanded to national meteorological offices and radiation protection agencies, which make use of long-range, transport and dispersion models coupled with meteorological forecasts to support the national decision making process. When managing the trans-national character of a release at long range, there are aspects that are of crucial relevance: - The real time accessibility to several model results concerning the prediction of the dispersion in order to base counter action on a wider spectrum of forecasted scenarios. - The possibility to verify, during the accident, the reliability of the model predictions in quantitative and qualitative terms by estimating the overall consistency of the predictions and the forecast uncertainty. Towards the fulfilment of these tasks, the ENSEMBLE system has been developed and is presented in this paper