Supershot to limiter H-mode transitions have been studied on TFTR. In several cases an edge poloidal rotation was observed prior to the initial Dalpha drop at the transition. This spin-up is consistent with formation of a radial electric field, -Er. The Del pI contribution to Er is approximately 30 kV/m and the density fluctuation level is reduced by a factor of 1 to 1.5 over a 5 cm region at the plasma edge across the transition.