Refer to figure.
Gradient Wind

The gradient wind is similar to geostrophic wind, but instead of straight isobars, they are curved, and therefore the wind moves in a curve also. It is therefore acted upon by a third force, instead of just pressure gradient force and coriolis force, it also has a centrifugal force component, which is a force pushing the air outwards from the bend. Now centrifugal force doesn't technically exist and is actually just inertia against centripetal force, but EASA seem incapable of admitting that very basic fact and have stuck with questions based around centrifugal force, so for this explanation we will also stick with this notion of centrifugal force.

For geostrophic wind, the pressure gradient force (PGF) always acts from high to low pressure, and the coriolis force (CF) always acts perpendicular to the wind (to the right in the Northern Hemisphere, left in the Southern Hemisphere). Eventually, these two even out until the wind flows directly along the isobars and the PGF=CF in magnitude, with the wind at a certain speed. (figure 1)

Importantly, the wind speed (and latitude) are what influence the coriolis force (CF); the faster the wind, the greater the CF (and vice versa).

Therefore, when isobars are curved around a low pressure (cyclonic) zone, the PGF is the same, but the coriolis force does not have to work as hard, as the centrifugal force is providing a helping hand in the same direction. As the coriolis force is weaker, this means that the wind will have a lower speed.

• Low pressure --> PGF = Coriolis Force + Centrifugal Force

The opposite is true for a high pressure (anticyclonic) region, where the coriolis force must equal the PGF + centrifugal force, and therefore the coriolis force is higher and the wind speed has to be stronger.

• High pressure --> PGF + Centrifugal Force = Coriolis Force

Therefore, high and low pressure regions have their named effects on gradient wind speed:

• A high pressure region causes a higher speed gradient wind; and
• A low pressure region causes a lower speed gradient wind.

Note: In most questions we will explain this in terms of centripetal force and an imbalanced PGF and CF, as that is the scientifically accurate (and slightly easier - in our opinion) way of understanding this.