Introduction

The Lothar storm that swept across Europe during 24-27 December 1999 is provided as a sample case study to use with OpenIFS. This storm was one of several storms to hit Europe in December 1999 and Lothar severely affected northern France, Switzerland and Germany (for more details see: Ulbrich et al., 2001, Weather, 56, 70-80). These storms were characterized by record-breaking windspeed observations and rapid development across Europe. There was also a band of extremely high baroclinity near the cyclone track over the N. Atlantic and partly into Europe associated with Lothar. The ECMWF forecasting system of the time did not accurately capture the storm's intensity. More recently, Wedi et al, 2012, ECMWF Newsletter, have shown that very high resolution (T7999; ~2.5km) is necessary to model accurately the high wind speeds observed, particularly over the mountainous regions of Europe.