The Met Office convective-scale ensemble, MOGREPS-UK

Since 2012 the Met Office has been running a short-range convective-scale ensemble prediction system over the UK, known as MOGREPS-UK. In this paper we consider MOGREPS-UK in its past, present and future configurations. We describe the evolution of the system during its first few years as an operational model and explain the rationale behind its development. The operational configuration of MOGREPS-UK is evaluated using neighbourhood verification techniques which allow the comparison of ensemble and deterministic forecasts in a probabilistic sense. We compare the performance of MOGREPS-UK to that of the higher resolution UK deterministic convective-scale model, the UKV, and show that over a three-month long trial MOGREPS-UK performs better for all variables considered. Plans of future upgrade options of MOGREPS-UK that take advantage of the increased computing capacity at the Met Office are discussed. Three different options were compared: increasing the domain size (now implemented), decreasing the horizontal grid-spacing, and increasing the number of ensemble members. Objective verification results from month-long winter and summer trials show that all options have their benefits, with the most improvement seen with the increase in ensemble size, particularly for precipitation.