Forest Fire Prediction and Analysis
| FOREST FIRES - Overview | FIRE PREVENTION | FIRE SUPPRESSION ||
FIRE BEHAVIOUR AND WEATHER
Predicting fire behavior is an art as much as it's a science. Even seasoned firefighters have trouble reading fire behavior and predicting fire's potential threat to property and lives. When they can't, the result may very well lead to tragedy.
Up-to-the-minute satellite mapping and weather information, remote sensing technologies, data evaluation, computer modelling, and internet communications have changed the face of fire behaviour analysis, thus putting the task of fire supression into a new dimension.
(See Mapping and Monitoring)
USDA Forest Service's Wildland Fire Assessment System
One tool kit at a fire bosses disposal is USDA Forest Service's Wildland Fire Assessment System. Daily bits of information are compiled at 1,500 weather stations throughout the United States and Alaska. The values of this data are used in assessing current wildfire conditions and you can find valuable information on the Internet. Every incident command center should have Internet connection to these sites.
Wildland Fire Assessment System
Fire Danger Maps - A fire danger rating map is developed using current and historical weather and fuel data. These data are transferred to models to give present condition information and also predicts what may happen tomorrow. Maps are developed to give a visual presentation of the potential danger of fire in a particular region.
Fire Weather Observations and Next Day Forecasts - Observation maps are developed from the fire weather network. The latest observations include the 10 minute average wind, the 24 hour rain total, the temperature, the relative humidity, and the dew point. There are next day forecasts displayed as maps as well.
Dead Fuel Moisture - Fire potential is heavily dependent on dead fuel moisture. There are four classes of dead fuel moisture - 10-hour, 100-hour, 1000-hour. When you have a drying of 1000-hour fuels, you have major potential for fire problems until a general soaking occurs.
Live Fuel Moisture/Greenness Maps - Live fuels also play a major part in the potential of fire. Vegetative "Greenness" determines fire spread. The greener the vegetation, the lower the fire potential. This map depicts the green you would expect to see from the air.
Drought Map - There are several maps that depict drought as determined by measuring soil and duff moisture. The Keetch-Byram Drought Index measures soil capacity to absorb water. Another index is the Palmer Drought Index which is linked to the National Climate Center Regional and updated weekly.
Atmospheric Stability Maps - The stability term is derived from the temperature difference at two atmosphere levels. The moisture term is derived from the dew point depression at a single atmosphere level. This Haines Index has been shown to be correlated with large fire growth on initiating and existing fires where surface winds do not dominate fire behavior.
Fire Weather Network - All the fire data used to create the above maps are retrieved from these stations throughout the continental United States.
The Canadian Forest Fire Weather Index (FWI) System
The Canadian Forest Fire Weather Index (FWI) System consists of six components that account for the effects of fuel moisture and wind on fire behavior.
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.
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.
Fine Fuel Moisture Code
The Fine Fuel Moisture Code (FFMC) is a numerical rating of the moisture content of litter and
other cured fine fuels. This code is an indicator of the relative ease of ignition and flammability of fine fuel.
Duff Moisture Code
The Duff Moisture Code (DMC) is a numerical rating of the average moisture content of loosely
compacted organic layers of moderate depth. This code gives an indication of fuel consumption in
moderate duff layers and medium-size woody material.
The Drought Code (DC) is a numerical rating of the average moisture content of deep, compact,
organic layers. This code is a useful indicator of seasonal drought effects on forest fuels, and amount of smouldering in deep duff layers and large logs.
Initial Spread Index
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 variable quantities of fuel.
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
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.
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