Frontal waves normally form on which types of fronts?

Frontal waves typically develop on slow-moving cold fronts or stationary fronts. This is because these types of fronts create atmospheric conditions conducive to the development of vortices, or secondary low-pressure areas, which enhance upward motion and result in cloud and precipitation formation.

In slow-moving cold fronts, the relatively warm and moist air is forced to rise over the cooler, dense air, leading to instability and the potential for storm development. Similarly, stationary fronts, where neither air mass is moving significantly, can also allow for the gradual build-up of low pressure, leading to the formation of frontal waves.

The options involving fast-moving warm fronts and high-pressure systems are less relevant when discussing the formation of frontal waves. Fast-moving warm fronts typically progress through more stable atmospheres, while high-pressure systems generally lead to clear and stable weather conditions, thus reducing the likelihood of wave formation. Therefore, the presence of slow-moving cold fronts or stationary fronts is crucial for the development of these frontal waves.