What does the code FU indicate?

The code FU indicates "Smoke." This code is part of the aviation weather reporting system and is used to signify the presence of smoke in the atmosphere, which can affect visibility and safety during flight operations. Smoke can arise from various sources, such as wildfires or industrial activities, and its presence is important for pilots and air traffic controllers to consider when assessing weather conditions.

Understanding these codes is essential for interpreting weather reports effectively, as they provide crucial information regarding specific weather phenomena that might impact flight operations or visibility. In this case, recognizing that FU specifically denotes smoke helps aviation personnel communicate and respond to potential hazards associated with reduced visibility.