When reporting observations that include layers, the lowest ceiling is determined by what criteria?

The lowest ceiling is determined by the lowest broken layer reported because ceilings refer to the height of the lowest layer of clouds that cover more than half of the sky. When assessing cloud cover, the criteria focuses on broken clouds, which are defined as layers that have 5/8 to 7/8 coverage of the sky. This means that the presence of broken clouds indicates a more significant obstruction to vision than other types, such as scattered clouds or those labeled as overcast, which do not affect the ceiling definition in the same context.

In contrast, the other options relate to different criteria that do not effectively establish the ceiling. For example, the layer with the most overcast may not necessarily be the lowest layer if there are broken clouds below it. Similarly, the layer with the least obscured visibility doesn’t relate directly to defining ceilings, as it focuses on visibility rather than cloud cover. Lastly, reporting the highest cloud layer present may overlook the important aspect of depth and coverage of lower layers, which is critical for accurately defining the lowest ceiling.