Impurity seeding of recycling impurities such as neon or argon, or non-recycling impurities such as nitrogen, is an essential element of power exhaust in future fusion reactors, including ITER. Aside from increasing the fraction of power radiated onto the main chamber, thus reducing the fraction carried by the plasma to the divertor, it also provides a viable method of ELM size reduction (mitigation) in ELMy H-mode plasmas. However, impurity seeding raises the risk of impurity accumulation in the core of the plasma, which degrades reactor performance and can lead to thermal collapse of the discharge. It is therefore imperative to understand the mechanisms of impurity transport in the boundary plasma, including the close field line (edge) region and the open field line (scrape-off layer or SOL) regions, and specifically, to quantify impurity influx across the magnetic separatrix and the 'screening' effect of the SOL. In this paper, we employ the two-dimensional transport code EDGE2D/NIMBUS to investigate the influence of (anomalous) parallel SOL flows, observed experimentally on JET and other tokamaks, on the 'screening' of a recycling impurity (neon). The parallel SOL flow is adjusted by external momentum injection, such that the Mach number at the top of the vessel varies from ∼0 to ∼0.5. Simulations indicate that the deuterium density in the plasma core increases by ∼50% over this range, in agreement with experimental findings (comparing normal and reversed field discharges). Notably, this density increase is associated with (caused by) plasma compression on the inboard side of the torus caused by the parallel SOL flow, thus leading to inverted radial density gradient and a recirculating flow pattern (convective cell) linking the inboard and outboard SOL regions. Simulations predict a 5% decrease in impurity (neon) concentration in the plasma core when the deuterium flow at the top of the vessel increases to Mach number, , with little change for higher Mach numbers.