If the prevailing visibility is two and one-half statute miles, how is it reported?

When reporting prevailing visibility, the standardized format is typically a numerical value followed by the abbreviation "SM," which stands for statute miles. In this case, "2 1/2SM" is the correct representation because it explicitly conveys the visibility in fractions, which can help clarify the measurement to those who are familiar with aviation and meteorological reporting.

Using "2 1/2SM" adheres to the conventions established by organizations such as the National Weather Service and the Federal Aviation Administration, ensuring that the report is clear and unambiguous. The usage of fractions is common in meteorological observations, allowing for precise reporting that can easily be understood by pilots, air traffic controllers, and other weather observers.

The other formats presented, while conveying the same numerical information, do not fit the conventional style. "2.5SM" is not incorrect but may be less preferred in some contexts where fraction format is standard. "2.5 miles" does not follow the abbreviation guidelines, and "2SM" understates the visibility reported. Therefore, the preference for "2 1/2SM" for reporting this specific measure is rooted in established meteorological conventions.