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Inserting random perturbations to winds at open lateral boundaries

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I am interested in running the em_quarter_ss idealized case, but creating an ensemble of simulations. One thing I'll be doing is perturbing the input sounding, which I know how to do. I'm also interested in introducing random perturbations at the lateral boundaries, which is commonly done in ensemble sensitivity analysis (ESA). Most of the time when lateral boundaries are perturbed for ESA, they boundary conditions are specified, so it's a matter of modifying the wrfbdy file. However, the em_quarter_ss case has open lateral boundaries and I don't think it would make sense to even try to specify the lateral boundaries for this case.

I'd like to perturb the u- and v-winds at the lateral boundaries. They're open lateral boundaries, so I know it'll require some modification to the WRF code to make this happen. I'm thinking that perhaps I just add a small random value to the u- and v-winds at the lateral boundaries at every time step. I'm looking for assistance in which array(s) I would need to add these random perturbations to, and where in the WRF code I would want to insert my code to add random perturbations.

I will really appreciate any suggestions and assistance with how to implement this in WRF.