A new ensemble design based on a set of analog forecasts is proposed (analog ensemble, AnEn).

The analog of a forecast for a given location and time is defined as the observation (or analysis grid point) that verified when a past prediction matching selected features of the current forecast was valid. The analogs are generated with the operational National Centers for Environmental Prediction (NCEP) North American Mesoscale model (NAM) and observations from hundreds of surface stations and tens of radiosondes over the continental U.S. for winds, surface pressure, and temperature, and over a period of one year. Attributes of the probabilistic prediction generated with AnEn are estimated, including reliability, resolution, sharpness, and spread-error consistency. The skill of AnEn is compared to a state-of-the-science operational system, the Environment Canada Regional Ensemble Prediction System (REPS), before and after calibration.