What is a key characteristic of a blocking anticyclone?

A blocking anticyclone is a high-pressure system that remains relatively stationary over a region for an extended period of time. This prolonged presence can obstruct or alter the normal progression of other weather systems, such as low-pressure areas or frontal systems, effectively "blocking" their movement.

The stability and persistence of a blocking anticyclone can lead to significant impacts on local weather patterns, including prolonged spells of fine weather or, conversely, the trapping of weather systems that could bring rain or storms. This characteristic of being stationary and effectively altering the flow of atmospheric conditions distinguishes blocking anticyclones from more transient weather systems.

The other choices reflect different phenomena or misconceptions about blocking anticyclones. For example, rapid weather changes are more typically associated with fronts or rapidly moving low-pressure systems, not the stable conditions brought by a blocking anticyclone. Similarly, blocking anticyclones do not enhance the development of cyclones; rather, they can inhibit their movement. Finally, blocking anticyclones can occur in any season, not solely during summer months. Thus, the defining characteristic of causing other systems to move less freely due to their stationary nature makes this option the correct answer.