Mechanistic models for complex atmospheric and hydrological processes are often used to simulate extreme natural events, usually in order to quantify the risks associated with these events. In this paper we use novel extreme value methods to analyse the statistical properties of output from a numerical storm surge model for the North Sea. The 'model data' constitute a reconstruction of the storm surge climate for the period 1955-2000 based upon a high quality meteorological dataset, and constitute the only available source of information on surge elevations at offshore and unmonitored coastal locations over this period. Previous studies have used extreme value methods to analyse storm surge characteristics, but we are able to extend and improve upon these analyses by using a local likelihood approach to provide a nonparametric description of temporal and spatial variations in the magnitude and frequency of storm surge events.