DTC GSI/EnKF help desk does not have resources to support GEN_BE.

To use GEN_BE, please downlowd latest WRF version.
GEN_BE is located under PATH_TO_WRF/var/gen_be.

A good reference for GEN_BE:

Descombes, G., T. D. Auligne, F. Vandenberghe, D. M. Barker, and J. Barre, 2015: Generalized background error covariance matrix model (GEN_BE v2.0). Geoscientific Model Development, 8, 669-696, doi:10.5194/gmd-8-669-2015.

Published Version: http://dx.doi.org/10.5194/gmd-8-669-2015