Certified Flight Instructor - Flight Instructor Airplane Practice Exam

When is vertical visibility reported in Terminal Aerodrome Forecasts (TAF)?

1. When the sky is overcast

2. When the sky is obscured

3. When the sky is partially obscured

4. When visibility is greater than 3 miles

The correct answer is: When the sky is obscured

Vertical visibility is reported in Terminal Aerodrome Forecasts (TAF) specifically when the sky is obscured. This typically occurs in conditions where ground-based visibility is significantly reduced, such as during fog, heavy precipitation, or other atmospheric conditions that obscure the horizon and lower levels of the sky, rendering it challenging to determine the ceiling based on standard visibility measurements alone. In such scenarios, the visibility upwards—referred to as vertical visibility—gives an indication of the distance one can see vertically through the obscuring phenomenon. Reporting vertical visibility in these cases is crucial for pilots who need to assess the conditions for safe flight operations and navigation. In contrast, options describing conditions where the sky is overcast or partially obscured do not dictate that vertical visibility must be reported, as overcast typically refers to a cloud cover situation that does not obscure visibility altogether. Additionally, reporting visibility greater than 3 miles wouldn't necessitate vertical visibility being noted since such conditions are usually considered acceptable for flight operations without obscuring significant limitations. Therefore, the correct identification of when vertical visibility should be reported aligns closely with situations where visibility is impacted by obstructions that hinder both horizontal and vertical perspectives.