 The horizontal domain of a model is either global , covering the entire Earth , or regional , covering only part of the Earth . Regional models ( also known as limited @-@ area models , or LAMs ) allow for the use of finer ( or smaller ) grid spacing than global models . The available computational resources are focused on a specific area instead of being spread over the globe . This allows regional models to resolve explicitly smaller @-@ scale meteorological phenomena that cannot be represented on the coarser grid of a global model . Regional models use a global model for initial conditions of the edge of their domain in order to allow systems from outside the regional model domain to move into its area . Uncertainty and errors within regional models are introduced by the global model used for the boundary conditions of the edge of the regional model , as well as errors attributable to the regional model itself . 
