Final answer:
Low-pressure systems occur when atmospheric pressure is lower than the surrounding environment. Movements of air masses influence global precipitation patterns. Pressure differences between areas can lead to strong winds and tornadoes.
Step-by-step explanation:
In terms of weather, low-pressure systems occur when the earth's surface atmospheric pressure is lower than the surrounding environment: Moist air rises and condenses, producing clouds. Movement of moisture and air within various weather fronts instigates most weather events.
The global pattern of precipitation is influenced by movements air masses. For example, there is a global belt of dry air masses and low precipitation at about 30° N and 30° S latitude.
The pressure in the atmosphere is an important factor in determining what the weather will be like. If the barometric pressure is high in an area, this will cause air to move to a region of lower pressure. The greater the difference in pressure between the two areas, the stronger the winds will develop. Under certain conditions, the winds can produce a tornado (a violent rotating column of air that reaches from a thunderstorm down to the ground).