What would a well-defined head of a fire indicate?

A well-defined head of a fire indicates that the fire is in an active and aggressive phase of burning, which is typically characterized by rapid spread. The head of the fire is the leading edge where the flames are most intense and are moving forward, often driven by wind, slope, and fuel availability. This indicates that the fire is exhibiting strong combustion characteristics, which can create a fast-moving front that poses a significant threat to anything in its path.

In contrast to a well-defined head, a shallow flame would suggest a less active fire, indicating low intensity and likely slower spreading behavior. Similarly, if the fire were slowing down, we would expect to see a less defined head, and if it were smoldering, the flames would be minimal or absent altogether. Thus, the presence of a well-defined head is a clear indicator of a fire's rapid spread and dynamic behavior.