How would you classify an observation reporting that visibility is "varies rapidly”?

The classification of visibility as "varies rapidly" indicates that the visibility conditions are changing frequently and can fluctuate significantly within a short time frame. This is consistent with the definition of variable visibility, where the observer notes that visibility is not steady and can change dramatically due to factors such as fog, precipitation, or obstruction by nearby features.

In contrast, steady visibility would imply that the visibility remains constant over time, consistent visibility suggests uniform conditions without significant changes, and unmeasurable visibility indicates that visibility is so poor that it cannot be quantified. Since "varies rapidly" does not fit any of those definitions, classifying it as variable visibility accurately conveys the nature of the observation.