What is indicated by a squall on a TAF?

A squall on a Terminal Aerodrome Forecast (TAF) indicates a sudden increase in wind speed that can significantly impact flight operations. Squalls are characterized by intense and often brief bursts of wind that can lead to rapidly changing weather conditions. This sudden change can also be accompanied by precipitation, which may reduce visibility. Pilots need to be aware of squalls because they can create turbulent conditions and affect aircraft performance during takeoff, landing, and while in flight. Understanding the implications of a squall helps pilots make informed decisions regarding their flight plans and safety measures.

While other options mention aspects of weather conditions, they do not accurately represent what a squall entails. For example, consistent low visibility and reduced flight speed do not capture the suddenness and potential severity of a squall, nor do they reflect the dynamic and often fleeting nature of squall conditions. Similarly, extended calm periods and gradual changes in cloud cover do not align with the typically abrupt nature of squall events, thus making option B the most accurate interpretation of what a squall signifies in a TAF.