Which data types are needed to perform an S-390 calculation?

• A. All of these
• B. Fuel data (fuel model/type and loading)
• C. Weather data (wind, temperature, humidity)
• D. Topography data (slope, aspect)

Answer: (A)

In this type of fire behavior calculation, inputs from multiple domains are essential because each one drives a different aspect of how a fire behaves. Fuel data, including the fuel model or type and how much fuel is present (loading), determine how much energy is released and how quickly fuels can burn. That directly affects the rate of spread, flame length, and intensity.

Weather data, such as wind, temperature, and humidity, shape how heat and flames are transported and how fuels dry out or resist ignition. Wind pushes flames and preheats fuels ahead of the fire, while temperature and humidity influence fuel moisture and ignition likelihood, all of which influence how fast and in what direction the fire moves.

Topography data, including slope and aspect, affects how fire climbs hills and how solar heating varies with exposure. Slopes often accelerate upslope spread and can channel winds, altering the fire’s behavior in ways not captured by fuels and weather alone.

Because these inputs interact—wind with slope, moisture with temperature, fuel type with wind—omitting any one of them would leave out a critical driver of fire behavior. Therefore, all of these data types are needed for a complete S-390 calculation.