The level of mercury can be read against a scale that measures the change in atmospheric pressure in inches of mercury movement. Typical pressures on Earth's surface vary from 28 inches to 31 inches. As the air flows from high pressure systems toward low pressure systems, it is deflected by the Coriolis effect. The winds spiral toward the low pressure center. This is called cyclonic wind movement.
Cyclones are low pressure systems with an organized circulation pattern.
The air also is deflected by the Coriolis effect when flows away from a high pressure system. Air flow away from a high is called anticyclonic . Because it is deflected by the Coriolis effect to the right as it travels, in the Northern Hemisphere the winds move away from the high pressure center in a clockwise direction. In the Southern Hemisphere, the winds move from the highs in a counter-clockwise spiral.