Predicting Wildfire Behavior Using Weather Data
Predicting wildfire behavior is as much an art as it is a science and very much based on understanding weather conditions that influence wildfire. Even seasoned firefighters have trouble reading fire behavior and in predicting a forest fire's potential threat to property and lives. One tool at a fire bosses disposal is USDA Forest Service's Wildland Fire Assessment System.
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 an Internet connection to these sites. USDA Forest Service's Wildland Fire Assessment System provides the support and supplies fire weather and mapping sources.
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.
Live Fuel Moisture/Greenness Maps
A fuel moisture index is a tool that is widely used to understand the fire potential for locations across the country. Fuel moisture is a measure of the amount of water in a fuel (vegetation) available to a fire and is expressed as a percent of the dry weight of that specific fuel.
Living fuels play a major part in the potential of fire. Vegetative "Greenness" is a major determinant and predictor of fire spread. The greener the vegetation, the lower the fire potential. This map depicts the green you would expect to see from the air.
Dead Fuel Moisture
Fire potential is heavily dependent on dead fuel moisture in forest fuels. 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.
Wildfire Drought Maps
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.