What sign suggests the atmosphere might be unstable?

The indication of smoke rising straight up suggests that the atmosphere is unstable. In unstable atmospheric conditions, warm air rises rapidly, which is evident when smoke from a fire or other source rises vertically without dispersing sideways. This upward movement of smoke indicates strong convection currents, characteristic of instability in the atmosphere.

When smoke rises straight up, it demonstrates that the surrounding air is cooler and denser than the air column heated by the fire or source, facilitating this rapid vertical movement. Unstable air is crucial for wildland fire behavior because it can lead to increased fire intensity and rapid spread due to the high convection rates.

Uniform smoke dispersal would typically occur in a stable atmosphere, where air movement is downwards or laminar, and doesn’t favor vertical growth. Thick cloud cover can indicate moisture and stable air. Heavy rain generally results from stable atmospheric conditions, which can suppress fire activity.