The dynamics of modulational interaction between short wavelength drift waves and long wavelength trapped ion convective cells are investigated. Modulational instability growth rates can exceed linear trapped ion mode growth rates. A simple set of envelope equations for this system has been derived and solved. A quasi-universal final state of dipolar anisotropic convective cells with trapped drift waves is indicated. Drift waves with kperpendicular to rho s>or=1 are trapped and undergo strong modulation.