Pressure and Wind

Why do we care if the air pressure increases or decreases? What has that got to do with the weather?

Differences in air pressure lead to differences in forces, as the barometer shows us. If this difference occurs out around us, rather than in our barometer, it produces a pressure gradient across the land that leads to a pressure gradient force pointing from high pressure to low pressure. This pressure gradient force is the origin of wind.

On the Earth, the motion of air (wind) becomes more complicated due to the rotation of the Earth and the friction of moving air across the land surface. In part, these effects cause the air in high and low pressure centers to circulate around the center of the pressure system.