Ignition of several individual fires throughout an area, either simultaneously or in rapid succession, and so spaced that they add to and influence the main body of the fire to produce a hot, fast-spreading fire condition.

Trough, Trough Aloft, Upper Level [Cold] Low: An elongated area of relatively low pressure, at constant altitude, in the atmosphere. The opposite of an upper level ridge. Upper level troughs are usually oriented north-south with the north end open. That is, air currents moving from west to east around the earth flow around three sides of the trough then turn eastward rather than toward the west, as in the case of a closed circulation. A large upper level trough may have one or more small upper level closed low circulation systems within it. 

Small gasoline-driven pump that can be carried to a water source by one or two firefighters or other conveyance over difficult terrain.

Hard suction hose or discharge hose carried connected to pump, eliminating delay occasioned when hose and nozzles must be connected and attached at fire.

A qualitative assessment of the heat pulse directed toward the ground during a fire. Burn severity relates to soil heating, large fuel and duff consumption, consumption of the litter and organic layer beneath trees and isolated shrubs, and mortality of buried plant parts. 

Degree to which a site has been altered or disrupted by fire; loosely, a product of fire intensity and residence time.

See fire severity

An inversion caused by subsiding air, often resulting in decreased atmospheric mixing conditions.

The comparative differences of damage to objects resulting from the fire’s passage.

Any staffed ground vehicle capable of providing medical services.