What causes surface winds to flow across isobars at an angle?

Surface winds flow across isobars at an angle primarily due to surface friction. Near the Earth's surface, friction interacts with the wind, slowing it down compared to the winds aloft. As a result, this frictional force alters the direction of the wind away from the geostrophic balance that is present at higher altitudes, where winds typically flow parallel to isobars. The surface friction decreases the wind speed, weakening the Coriolis effect, which would normally cause the wind to naturally curve. Consequently, the result is that winds flow across isobars toward lower pressure rather than parallel to them.

Understanding the role of surface friction is crucial in meteorology. This phenomenon becomes especially important in weather systems near the ground where terrain, vegetation, and other surface features can significantly influence wind patterns.