What does it indicate when the isobars on surface analysis charts are close together?

When isobars on surface analysis charts are close together, it indicates that the pressure gradient force is greater. This is because the pressure difference between two points is more pronounced when the isobars are in close proximity. A strong pressure gradient results in accelerated air movement from high to low pressure areas, leading to faster wind velocities.

The relationship between isobar spacing and wind speed is well established in meteorology: the closer the isobars, the stronger the forces acting on the air, which in turn causes more turbulent and high-velocity winds. Therefore, observing closely spaced isobars on a chart helps forecasters determine areas of potential storm activity, as these strong winds can contribute to severe weather conditions.

In contrast, when isobars are far apart, it usually signifies a weaker pressure gradient, which results in lighter winds, not the strong velocities indicated by the chosen answer. This understanding is crucial for both weather prediction and for pilots operating lighter-than-air craft, as they must navigate and respond to these wind conditions effectively.