What is the only cloud type forecasted in TAF reports?

The correct answer is cumulonimbus. TAF (Terminal Aerodrome Forecast) reports provide vital aviation weather forecasts, typically covering a 24- or 30-hour period, and focus on significant weather phenomena that could affect flight operations. Cumulonimbus clouds are particularly important in these reports because they can indicate severe weather conditions such as thunderstorms, heavy precipitation, and turbulence. This specific cloud type is closely monitored and forecasted as it poses greater risks to aviation safety due to its association with intense weather events, making it essential information for pilots.

In contrast, the other cloud types mentioned, such as cumulus, stratus, and nimbus, are not specifically singled out in TAF reports as significant concerns for aviation operations in the same way as cumulonimbus. While these clouds can certainly affect flight conditions, the primary focus of TAF reports is on those clouds that have the highest potential to disrupt flying, which underlines why cumulonimbus is the correct choice for what is forecasted in TAF reports.