The purpose of a weather map is to give a graphical or pictorial image of weather to a meteorologist. As a forecasting tool, weather maps allow a meteorologist to see what is happening in the atmosphere at virtually any location on earth. Complex three-dimensional models of weather systems can be made by collecting weather data at multiple levels in the atmosphere. Computers then compile that information to produce the pictures that weather scientists analyze. In the early days of meteorology, these pictures were all drawn by hand!