A low, or a low pressure area, is a region of rising atmospheric air. Active weather on Earth is defined by the presence of lows, which generally produce cloud, strong winds, and precipitation.
Low pressure areas may be formed in one of three ways. On Earth, they are most commonly found at the equator and at about 30°N/S latitude, where they come about as a result of the combination of the rising of hot, moist air and the convergence of global wind belts. Frontal lows are temperate zone phenomena, and develop along the polar front as a result of the interaction between cold and warm surface air masses. Thermal lows also form over areas such as Death Valley as the result of intense ground heating; they are much smaller in geographic extent than either convergence lows or frontal lows.
A low pressure area, or a low for short, is a region where the atmospheric pressure is lowest with relation to the surrounding area.
Lows are frequently associated with stronger winds and atmospheric lift.
Surface low pressure systems will tend to be smaller in area and have stronger surface winds than a given high pressure system, due to the addition of surface friction to the pressure gradient force and coriolis effect that drive the circulation.
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