9. The following illustration (figure 9) shows a grid-based model of fire progression. The darkest cells in the grid represent the area where a fire is currently underway. A fire probability model which incorporates fire behavior in response to environmental conditions such as wind and topography delineates areas that are most likely to burn in the next two stages. These areas are represented by lighter shaded cells. Fire probability models are especially useful to fire fighting agencies for developing quick-response, effective suppression strategies.