What drives the initial movement of wind across isobars?

The initial movement of wind across isobars is primarily driven by the pressure gradient force. This force arises due to differences in atmospheric pressure between adjacent areas. When there is a pressure difference, air moves from areas of high pressure to areas of low pressure, creating wind. The greater the pressure difference over a given distance, the stronger the wind will be.

Isobars on a weather map connect points of equal atmospheric pressure. When these lines are closely spaced, it indicates a steep pressure gradient and thus a stronger pressure gradient force, leading to faster winds. This foundational principle of meteorology explains why the pressure gradient force is critical in initiating and determining the direction of wind flow across isobars.

While factors such as the Coriolis effect, Earth's rotation, and friction with the ground do influence wind patterns and ultimately affect wind direction and speed, they do so after the initial movement dictated by the pressure gradient. Understanding the pressure gradient force is essential for grasping how wind begins to move across isobars in the atmosphere.