How are squall lines indicated in a TAF report?

Squall lines in a TAF report are indicated by mentioning "TS" for thunderstorms, which often occur along these lines, or "OCNL," which refers to occasional occurrences of these phenomena. Squall lines are significant weather features that can produce severe thunderstorms, and TAF reports aim to provide pilots with essential information about conditions that may affect flight safety, including the presence of thunderstorms.

The mention of "TS" captures the intensity and nature of the severe weather that squall lines can bring. Additionally, "OCNL" suggests that these activities may not be continuous but can occur sporadically, which accurately reflects how squall lines can behave. Thus, recognizing these terms in a TAF is crucial for understanding the potential for adverse weather associated with squall lines.

The other options such as "WIND," "SHOWER," and "RAIN" do not specifically denote squall lines or the severe weather typically associated with them, as they are more general terms used for a variety of weather scenarios that may not indicate the presence or impact of squall lines directly.