In significant weather charts, the term OCNL indicates what about thunderstorm coverage?

In significant weather charts, the term OCNL stands for "occasional," which specifically refers to the occurrence of cumulonimbus clouds, or CBs, in a less dense and more sporadic manner. This notation indicates that the thunderstorms are not happening continuously but rather are present as well-separated instances.

The use of “well-separated” implies that while there might be thunderstorms occurring, they are not clustered tightly together; they are spaced out adequately, allowing for clear areas in between. This gives pilots and meteorologists a better understanding of the potential for isolated weather events rather than a widespread area of severe weather.

Understanding the designation is important for flight planning, as it helps assess potential turbulence and other weather-related impacts to flight safety. The other options would suggest different densities and distributions of thunderstorms, which would not align with the meaning of "OCNL."