This program will pick a random SimSig simulation for you to run, with the name of the simulation, and all parameters, such as ARS, TORR, and Adverse Weather, randomly chosen as appropiate. You can change the options prior to running the simulation itself as much as you like, this page only suggests the options for you.
Select the simulations you would like enabled in the rotation. Any simulation that is not checked will not be picked at random. All simulations are enabled by default; you can disable simulations you either do not own or do not want included in the rotation. (Ctrl+F to find a sim if you need to.)