I have a set of data which histogram looks like this:
The values are not normally distributed since the distribution is not simetric.
For another set of data that is normally distributed, I have used a Ornstein-Uhlenbeck stochastic process to generate representative values.
Since OU processes only work with normally distributed data, what can I use to represent the depicted data set?
Thanks.

If the forecasts are generated separately and independently, then you shouldn't try to model the errors with a time series. You should simply fit a distribution to them - perhaps a composite normal or something.
– zab Dec 06 '16 at 14:53