The one-level (one for the plasma cloud and neglect of cloud-background ionosphere interaction), two-dimensional fluid equations modeling striation development in large F region ionospheric plasma clouds have been numerically solved, by using an initial one-dimensional cloud geometry, for three different initial Pedersen conductivity gradient scale lengths L=3, 6, and 10 km. In the nonlinear regime, evidence is presented for an outer scale size of well-developed striations in a direction (y) perpendicular to the E¿B drift (&khgr;) of the plasma cloud whose initial Pedersen conductivity varies only along the drift direction. The perpendicular outer scale size 2&pgr;/k0y is proportional to the initial gradient scale length L through a constant of order unity, i.e., k0yL/2&pgr;?1. In addition, for the three scale lengths L studied, the one-dimensional &khgr; power spectra ∝k&khgr;-n&khgr; with n&khgr;?2 for 2&pgr;/k&khgr; between 1 and 80 km. while the y power spectra ∝ky-ny with ny?2--2.5 for 2&pgr;/ky between 1 and 10 km. These results are consistent with recent experimental and theoretical studies of plasma cloud striations.