What does "FM" indicate in a TAF?

In a Terminal Aerodrome Forecast (TAF), "FM" stands for "Forecast change beginning." This term is used to denote a specific point in time when a significant change in the forecast conditions is expected to start. Following the "FM," the TAF will typically specify the date and time along with the new weather conditions anticipated from that moment onward. This helps pilots and aviation personnel prepare for upcoming weather changes that could impact flight operations.

The other options do not accurately describe the meaning of "FM" in the context of TAFs. "Formulation of meteorology" does not relate to operational forecasting terminology, while "Forecast modification" implies an alteration to an existing forecast rather than the initiation of new conditions. Lastly, "Frequency of meteorological events" does not convey the intended meaning as it focuses on the occurrence of events rather than the timing of changes in forecast conditions. Thus, understanding that "FM" marks the beginning of a forecasted change is crucial for interpreting TAFs accurately in aviation meteorology.