Probability throughout the simulations is handled using pre-rolled random numbers based on a fixed seed, so that simulation results are reproducible.

Probability is stored as 'thresholds' for a certain event on a day-by-day and hour-by-hour basis. If the calculated probability of that type of event matches or exceeds the threshold then the event will occur.

Each iteration of a scenario will have its own thresholds, and thus different behaviour can occur with the same input indices.

Thresholds are used to determine:

• extinction
• spread events