Within a body of air, there may be pockets that have a certain characteristic and behavior of their own. These are known as “eddies”. The activities of the eddies can influence the activity of the larger air mass. Eddies are most commonly noticed around structures. Just as water changes its behavior as it moves around rocks, so does air as it moves around buildings. Other factors that influence eddies can be temperature differences. The driving force is the pressure irregularities in the system. These eddies can be important, whether you are considering the water demands in various parts of your garden, or how a fly ball will respond in a corner of the baseball stadium.
Mary Knapp, Weather Data Library