Weather occurs on all scales, from the smallest swirl of wind to the largest storm system. Global patterns of motion include jet streams. The jets streams control the movement of systems on the synoptic scale, such as high and low pressure systems. Low pressure systems contain thunderstorms. Thunderstorms contain many smaller motions, including microbursts and mini-cyclones. Each of these is a downward progession in weather scales. In session 5, we will discuss these phenomena scales, as well as time and grid scales, which are important in numerical modeling.