MILAGRO was a large inter-agency field campaign designed to evaluate the regional impact of the Mexico City urban plume. Detailed meteorological simulations are a necessary component in the analysis of the data collected. Mesoscale meteorological simulations from the Weather Research and Forecast model (WRF) are evaluated against both data and previous MM5 simulations. Detailed land surface information from satellite remote sensing is used to estimate the surface heat budget, which is a determining factor in the wind pattern in the Mexico City basin. The FLEXPART Lagrangian trajectory model is used to identify representative wind patterns and residence times. Verification is carried out by comparing with actual balloon trajectories as well as by analysis of carbon monoxide dispersion. This analysis provides a description of Lagrangian experiments and Lagrangian time scales for use by experimentalists at both fixed and mobile sites.