In the case of multiple observations, which is the standard for documenting the prevailing visibility?

Documenting the prevailing visibility involves calculating the mean of all reported visibility values. This approach is used because it provides a comprehensive picture of visibility conditions over a certain area instead of relying on a single observation that might be affected by temporary conditions or localized phenomena. By averaging all observed values, you account for variations and ensure a more representative and objective assessment of the prevailing visibility. This method reflects the overall conditions experienced during the observation period and aligns with standard meteorological practices for documenting visibility.

Choosing only the best visibility could overlook significant variations, while relying on the latest observation might not capture the true character of visibility over time. Calculating the maximum reported value may also give a skewed view if the highest value was not indicative of the majority of conditions present. Thus, using the mean serves to balance these factors effectively.