A subjective assessment of the health of individual plants in similar site and growing conditions; or a more specific measure based upon a specific facet of growth, such as seed stalk or tiller production per plant or per unit area.

Generally, wind speeds and wind directions at various levels in the atmosphere above the domain of surface weather observations.

An obstruction-free circle around the (helicopter) landing pad.

Person whose principal function is fire suppression.

An agent that extinguishes the flaming and glowing phases of combustion by direct application to the burning fuel.

Applies to radio frequencies primarily used for air operations.

Stage of growth or degree of flammability of vegetation that forms part of a fuel complex. Herbaceous stage is at times used when referring to herbaceous vegetation alone. In grass areas minimum qualitative distinctions for stages of annual growth are usually green, curing, and dry or cured. 

The 24-hour clock system where midnight is 2400, one minute after midnight is 0001 and progresses to 2400 daily.

The fuels that support the flaming front of the moving fire.

Total allowable weight of a loaded aircraft for takeoff or landing, adjusted for altitude differences.