Forest Fire Watch: Fire Danger

Fire Danger ( click for map ) is a relative index of how easy it is to ignite vegetation, how difficult a fire may be to control, and how much damage a fire may do.

Low		Fires likely to be self-extinguishing and new ignitions unlikely. Any existing fires limited to smoldering in deep, drier layers.
Moderate		Creeping or gentle surface fires. Fires easily contained by ground crews with pumps and hand tools.
High		Moderate to vigorous surface fire with intermittent crown involvement. Challenging for ground crews to handle; heavy equipment (bulldozers, tanker trucks, aircraft) often required to contain fire.
Very High		High-intensity fire with partial to full crown involvement. Head fire conditions beyond the ability of ground crews; air attack with retardant required to effectively attack fire's head.
Extreme		Fast-spreading, high-intensity crown fire. Very difficult to control. Suppression actions limited to flanks, with only indirect actions possible against the fire's head.

The Canadian Forest Fire Weather Index (FWI) System is a model that predicts the potential fire danger within the forest. This is achieved by modeling the dryness of the forest fuels (those parts of the forest that burn) and the potential fire behaviour (how fast and intense a fire may become).

The FWI system consists of six components that account for the effects of fuel moisture and fire behaviour. The first three components are fuel moisture codes and are numerical ratings of the moisture content of litter and other fine fuels, the average moisture content of loosely compacted organic layers of moderate depth, and the average moisture content of deep, compact organic layers.

• Fine Fuel Moisture Code (click for map)
  The Fine Fuel Moisture Code (FFMC) is a numerical rating of the moisture content of litter and other cured fine fuels. This is made up mostly of dead and down needles and leaves, as well as lichens, mosses and other small, loose debris. The FFMC is an indicator of the relative ease of ignition and flammability of fine fuel.
  
  
• Duff Moisture Code (click for map)
  The Duff Moisture Code (DMC) is a numerical rating of the average moisture content of the duff layer: a layer of loosely compacted organic layers of moderate depth on the ground. The DMC gives an indication of fuel consumption in moderate duff layers and medium-size woody material.
  
  
• Drought Code (click for map)
  The Drought Code (DC) is a numerical rating of the average moisture content of deep, compact, organic layers in the floor of the forest. The DC is a useful indicator of seasonal drought effects on the forest fuels, and amount of smouldering in deep duff layers and large logs.

The remaining three components are fire behavior indexes which represent the rate of fire spread, the fuel available for combustion, and the frontal fire intensity; their values rise as the fire danger increases.

• Initial Spread Index (click for map)
  The Initial Spread Index (ISI) is a numerical rating of the expected rate of fire spread. It combines the effects of wind and the Fine Fuel Moisture Code on rate of spread without the influence of different fuel types.
  
  
• Buildup Index (click for map)
  The Buildup Index (BUI) is a numerical rating of the total amount of fuel available for combustion that combines the Duff Moisture Code and the Drought Code.
  
  
• Fire Weather Index (click for map)
  The Fire Weather Index (FWI) is a numerical rating of fire intensity that combines the Initial Spread Index and the Buildup Index. It is suitable as a general index of fire danger throughout the forested areas of Canada.Structure of the FWI System

Information courtesy of Natural Resources Canada.