If the station anemometer is not in operation, and the observer estimates that the wind speed is 10 knots, how will this be reported?

When reporting wind speed, the specific condition of the anemometer is crucial. In situations where the anemometer is not operational, the observer must rely on visual estimation. In this case, if the observer estimates the wind speed to be 10 knots, it will be reported simply as "10."

This is because, during an observation, if the wind speed is directly observed or estimated, it is conveyed in knots without any additional notation or modification, provided that the estimate was made with due diligence. The absence of any prefix or suffix in the report indicates that it was a direct observation or a reasonable estimate.

Other reporting formats, such as using "M" or "E" to indicate an estimated or missing value, come into play under different circumstances. For example, "M" often indicates a "missing" value, generally used in cases where no estimation is made, while "/M" denotes that the wind observation is below the threshold of measurable values. However, since the observer has made an estimation, the proper notation is the wind speed in knots alone. Thus, reporting it as "10" accurately reflects the observer's estimation of the wind conditions.