Which of the following best describes the term "TEMPO" in a TAF?

The term "TEMPO" in a Terminal Aerodrome Forecast (TAF) specifically refers to temporary weather changes that are expected to occur over a short period of time, typically lasting for less than one hour within the forecast period. This designation is used to indicate that certain weather conditions, which might significantly affect flight operations, are anticipated to arise intermittently and are not continuous throughout the forecast validity period.

The other options describe different aspects of weather forecasting: "weather conditions that are expected to last" would imply more stable phenomena rather than temporary changes, while "long-term forecasts" does not accurately align with the short-term focus of TAFs. Non-significant weather phenomena, on the other hand, would not warrant a specific mention in the TAF, as "TEMPO" specifically includes weather events that may be impactful, even if they are fleeting. Therefore, "temporary weather changes" best encapsulates the meaning of "TEMPO" in a TAF context.