The Outputs
The output section of the NFDRS Structure chart is the components or simply the outputs that are based in fire behavior description, but expressed in the broader context of fire danger rating.
1. Spread Component (SC) - Displays a value numerically equivalent to the predicted forward rate of spread of a head fire in feet per minute. The SC is a function of fuel model characteristics, live fuel moistures, the 0 to 3-inch (76 mm) dead fuel moisture (heavily weighted to the 1-hour timelag fuels), wind speed and slope class. The SC is highly variable due to the effects of relative humidity, wind and live fuel moisture.
2. Ignition Component (IC) - Displays the probability of a firebrand causing an ignition requiring a suppression action.
3. KBDI - Keetch-Byram Drought Index
4. BI - The Burning Index (BI) is an NFDRS index relating to the flame length at the head of the fire. BI is an estimate of the potential difficulty of fire control as a function of how fast and how hot a fire could burn. It has been scaled so that the BI value divided by 10 predicts the flame length at the head of a fire. For example, a BI of 75 would predict a flame length of 7.5 feet (2.3 m). BI is a function of the Spread Component and the Energy Release Component, and has moderate variability. It is sensitive to fuel models, and can trace seasonal trends reasonably well for models with heavy dead or live components. Because it uses wind and relative humidity, it is also very sensitive to weather observation errors.
Read more about this topic: National Fire Danger Rating System