This paper reviews some general characteristics of atmospheric observations and numerical weather prediction methods which provide most of the fundamental data used by meteorologists providing operational environmental support. In general, these data have temporal, spatial, and informational shortfalls for providing real-time inputs for atmospheric transmission support. Meteorological models have improved significantly since first conceived back at the turn of the century and this trend is expected to continue. Improvements are a direct result of gains in the quantity and quality of observational data as well as rapid increases in computer technology which allow for more complete and higher resolution models. However, there still remain a number of deficiences with current observations and models that need to be considered by those concerned with electro-optical or other electro-magnetic transmission through the atmospheric environment.