I think you are getting closer to the way most of us think about models, but they are tools for forecasting (meteorologists literally use them as tools to do so) and they don't show every possible outcome. Without models, we would have no idea that it is going to get very cold next week, for example. Now, we don't know exactly what each shortwave is going to do 5-10 days away, but we do know the major players at 500 and the overall synoptic set-up that will drive the weather during this timeframe.