@nwindy
You have 2 types of weather forecast :
Deterministic
Ensemble
The first one is the one proposed by Windy models and gives you one forecast at a specific day and specific hour. There is no probability associated with this forecast because this is one single forecast calculated by the model deterministic.
Now, when we talk about ensemble weather forecasting, the model here doesn't calculate only one single forecast but a group of around 20 forecasts, each obtained by changing some parameters. From this ensemble of 20-21 forecasts at a specific day and specifc hour, you can extract data in this case with probabilities like 40% chance of rain for July the 15th at 3.00PM. This is very useful to be able to quantitify the incertitude on data
This ensemble approach looks great but because of the increase number of calculations (20-21), grid will be much bigger and therefore data will be less accurate