If the observed surface prevailing visibility is 10 statute miles and tower visibility is 4 statute miles, what value would be reported for the tower visibility?

In the context of aviation weather reporting, prevailing visibility refers to the greatest distance at which objects can be seen and identified across the majority of the horizon circle, while tower visibility pertains specifically to the visibility observed from the aerodrome control tower.

When reported values of visibility differ, the value of visibility that is used in official reporting is typically that which is less restrictive. This is because the lower visibility measurement is often more relevant for flight operations, particularly in or near the airport environment where operations on the ground and approach can be impacted by lower visibility levels.

In this scenario, with the prevailing visibility at 10 statute miles and the tower visibility at 4 statute miles, the tower visibility of 4 statute miles is the limiting factor for operations close to the aerodrome. However, if the requirement calls for selecting only one value to report, and that value must be relevant to aviation operations, the appropriate scenario might lead to a case where none would be explicitly reported in an official communication if both values were not used. This highlights the specificity and contextual use of visibility reports in aviation, which may lead to the option of reporting "none" under certain regulatory frameworks.

Understanding this context — how different visibility measurements apply to operational scenarios — is key to