The near-surface temperature, humidity, and wind obtained from NWP models come from direct model forecasts of those variables.

Of course, the dynamics of NWP models are calculated at all levels of the model grid, but that is only part of the story. The model physics must also come into play, not only at upper levels, but also at the lower boundary surface. The surface physics package, through its calculation of skin temperature, for example, necessarily has a major effect on the near-surface air temperature. Dynamics alone cannot account for how the model surface, or skin, affects the near-surface temperature, humidity, and wind. Rather, values of these variables obtained from the model dynamics must be “merged” in some fashion with those obtained from the surface physics. This process is often referred to as the “diagnosis” of near-surface variables. In this sense, the model does generate the values of those variables, but it does not directly forecast them on its grid.