The Impact of Radar and Satellite Imagery in a Mesoscale NWP System

Summary

The UKMO Mesoscale Model is used routinely to predict the weather over the British Isles on a 15 km grid. Synoptic scale development is largely controlled by the time-dependent boundary conditions. However the mesoscale evolution is sensitive to the initial conditions within the domain, and especially to the humidity distribution. The Interactive Mesoscale Initialisation (IMI) allows a forecaster to monitor the use of surface observations, satellite and radar imagery in the production of a set of key analyses of surface variables and the cloud distribution. Conceptual models are then used to make the remaining model fields consistent with these analyses. Thus, an inverse of the model’s precipitation scheme is used to initialise cloud water content from the analysed cloud cover profile and the surface precipitation rate. The results are presented for two cases of interest, taken from an assessment programme which is currently underway: An anticyclonic stratocumulus forecast and a frontal precipitation forecast. It is illustrated how, in these cases, the use of satellite and radar data within the framework of the IMI produced a better set of initial fields which in turn resulted in improvements to the forecast.