A long-range forecast is a forecast for a period of 1 month to 2 years. The subject of long-range forecasting is not the weather, but generalized statistical characteristics of the atmosphere, for example, averaged values of meteorological elements or their anomalies.
A long-range forecast provides useful information for various sectors of the economy in terms of long-range planning and implementation of risk management activities.
In long-range forecasts, a coupled “atmosphere-surface” system is considered. The system takes into account the influence of external slow impacts on the atmosphere, for example, anomalies in ocean surface temperature, soil moisture, and temperature, in the extent and thickness of sea ice and snow cover. These parameters change much more slowly than the weather, but bring signals into long-range atmospheric changes. Currently, the basis of long-range forecasts is physically complete multi-component global numerical models, such as general circulation models of the atmosphere, ocean, land surface, sea ice, small gas components, etc.