Violent convection caused by a large continuous area of intense fire. Often characterized by destructively violent surface indrafts, near and beyond the perimeter, and sometimes by tornado-like whirls.

Any sudden acceleration in rate of spread or intensification of the fire. Unlike blowup, a flare-up is of relatively short duration and does not radically change existing control plans.

Sudden increase in fireline intensity or rate of spread of a fire sufficient to preclude direct control or to upset existing suppression plans. Often accompanied by violent convection and may have other characteristics of a fire storm.

The requirement to perform satisfactorily in a specified position within the last five years (three years for aviation and expanded dispatch positions) in order to maintain qualification for the position.

Setting fire to more than one strip of fuel and providing for the strips to burn together. Frequently done in burning out against a wind where inner strips are fired first to create drafts which pull flames and sparks away from the control line.

There are two subsets of the white ash fire indicator, deposits and exposure.

Objects displaying more white ash deposits on the exposed surface of the object as opposed to the protected surface of the object indicating the direction of fire progression at that location.
Objects displaying more attached white ash on the exposed surface of the object as opposed to the protected surface of the object indicating the direction of fire progression at that location.

One of the 11 NWCG categories of fire pattern indicators.

A physical object that displays changes (fire effects) from exposure to heat, flame, and combustion by-products that can reveal the direction of fire progression at a precise location with accurate analysis. A fire pattern indicator is a single component of the overall fire pattern.

The larger area where the fire first established itself and is identified by an analysis of the fire behavior context, macroscale fire pattern indicators, and witness statements.

A trial pass over the target area by a leadplane and/or an airtanker to pinpoint target areas and warn ground personnel of the impending retardant or extinguishing agent drop.

Stage of a fire at which all surfaces and objects within a space have been heated to their ignition temperature, and flame breaks out almost at once over the surface of all objects within the space.