The IFS models the dynamics of the atmosphere and the physical processes that occur, and also other processes that influence the weather e.g. atmospheric composition, surface energy fluxes, the marine environment and processes at the atmosphere/surface interface (then scroll down to soil/surface section). Several configurations of the atmospheric model are used, each tailored towards a specific aim (HRES for detail in the forecast during the first 10 days, Ensemble (ENS) to investigate uncertainty in the forecast during the first 15days, and extended ENS and Seasonal runs to give probability of general conditions at longer ranges). There are some slight differences, but generally the same model structure is used in each of the different model configurations. The relative skill of the models and their strengths have been investigated.