To further enhance the predictability of NCEP global ensemble forecast system, we introduce the initial perturbations generated by the Ensemble Transform

(ET) and ET with rescaling methods and compare with operational breeding ensemble in NCEP operational environment. Different rescaling strategies

are experimented and compared.

Both ET and ET with rescaling belong to the second generation methods and generate the initial perturbations that are consistent with the operational data assimilation (DA) system. The best possible initial analysis error variance from DA is used to restrain the initial perturbations

that are orthogonal with respect to an inverse analysis error variance norm. The simplex transformation (ST) imposed ensures that the initial perturbations are centered and span a subspace with maximum number of degrees of freedom.