The way NWP data is retrieved, interpolated and presented can affect the indicated value of the parameters as forecast by the IFS models at a given location. ECMWF forecast products can be retrieved on a wide range of spatial resolutions, from regular and rotated latitude-longitude grids to the original. The data can be retrieved from the IFS models on pressure, theta (isentropic) or potential vorticity (PV) levels, depending upon the parameter. Forecast temperature, wind, specific humidity, geopotential etc are stored in spectral components but can be interpolated to any specified latitude-longitude grid. This interpolation can also be applied to near-surface parameters. However the native storage method for the near surface parameters is a (cubic octahedral) grid, and so direct use of these, particular gridded values, is strongly recommended, especially for precipitation and other surface fluxes to avoid the undesired effects of interpolation.