A forecast based on a systematic statistical examination of data representing past observed behaviour of the system to be forecast, including observations of useful predictors outside the system. In short-term climate forecasting, CCA (canonical correlation analysis), as described by Barnston (1994), is a good example of a statistical forecast. Depending on method and scope, the limitations of statistical forecasts are related to shortness of record, danger of overfitting, assumptions of linearity (often), absence (often) of physical considerations, etc. Purely statistical forecasts in weather forecasting have become rare; however, a combination of dynamical model output and statistics is very common in weather forecasting. Some statistical methods are guided by physical principles to such an extent that they resemble dynamical models. An example of the latter is empirical wave propagation described by Qin and van den Dool (1996). See perfect prognosis method, MOS.