Alberta is bone-dry
The Canadian Forest Fire Weather Index (FWI) is a system for determining the fire danger in an area. Daily observations of temperature, relative humidity, wind speed and 24-hour rainfall are taken in order to calculate the relative moisture content of the soil and organic ground cover, which in turn is used to predict how a fire would behave.
Parts of Alberta, particularly in the northwest, have been exceptionally dry for the past 12 months. With drought conditions present even in deep, compact soil, fires are easily ignited.
An unwinnable fight?
The most effective way to suppress a large fire is by dropping water on it from the air; however, during peak burning, which usually occurs in the late afternoon, the heat from the flames is so intense that water can evaporate before it reaches the ground.
Fighting fires is easier at night, when winds are calmer and humidity is higher, but as water bombers cannot fly at night, suppression efforts must be undertaken by personnel on the ground.
Ultimately, a change in the weather is what is needed to bring the Fort McMurray fire under control, but current forecasts show it could be more than a week before the region sees any substantial precipitation.
Infographic: Alissa Dicaire/Alexandra Pope