Verification of Precipitation Forecasts from the UK Operational Limited-area Model

Abstract

 Precipitation forecasts from the UK operational limited-area model have been verified and some results are presented here. Total forecast precipitation over 6-month summer and winter seasons is compared with high-resolution data obtained from the UK raingauge network. In general good agreement is found between the model and observations though some systematic errors are evident. In particular precipitation over high ground in the west and north of the UK is underforecast. Forecasts of 6-hour accumulations are assessed by comparing with observations from 369 stations over the European area covered by the model. Threat scores are given for threshold values of 0.05 and 2.0 mm and for various forecast periods. It is found that frontal rain is usually well forecast. A separate assessment was made of the representation of fronts in the model; 72 percent of 24-hour forecasts of frontal position over the UK are found to be within 100 km of the verifying position.