Overview

Meteorological evaluation of the OpenIFS outputs is demonstrated here on case studies. Two weather events have been chosen in order to show the model's capabilities on the one hand, and on the other hand, to provide reference cases for the users (to compare the results of their installed model version with the ones run at the ECMWF or to inter-compare the results of different model versions). Important aspects at selection of the cases were their geographical scope and their physical background, i.e., those storm events were preferred which had severe impact over Europe and were governed by large-scale dynamical forces. Cases both with weak and good operational forecast skill were considered.

Case studies

Storm Desmond

Storm Desmond caused severe flooding, travel disruption and a power outage across northern England, parts of Scotland and Ireland on 5 December 2015. Cumbria in northwestern part of England is one of the worst affected regions with more than 200 mm of rain in 24 hours recorded in that area. Storm Desmond broke the United Kingdom's 24-hour rainfall record, with 341.4 mm of rain falling in Honister Pass, Cumbria. On Saturday, 5 December, UK Met office issued a red warning of heavy rain for Cumbria. The cyclone also led to flooding in southern Norway.

Orographical enhancement of precipitation played a major role in the event and the operational model of the ECMWF picked well the highest rainfall amounts over the orographical barriers. However, the forecast underestimated the peak values of about 100 mm in 24 hours in Cumbria and overestimated the precipitation amount in lee of the hills (Figure 1).

Figure 1: 24-hour precipitation amount (mm) between 6 UTC 5 December and 6 UTC 6 December 2013, based on observations (top) and ECMWF operational IFS forecast (bottom).

users can check their model installation with a short acceptance test on T21 resolution. The meteorological evaluation framework makes it possible also to assess the meteorological performance of OpenIFS based on two sets of case studies.

We chose two weather events which had been predicted originally with different skill. Several model experiments were carried out Several OpenIFS experiments have been conducted for this case with the aim to test the effect of starting date and , forecast length, initial condition as well as spatial resolution to on the forecast quality. The details of experiments are summarized in Table 1.

Table 1:  Settings of the experiments achieved for Storm Desmond.

model outputs are visualized and evaluated using Metview.

After introduction of the two cases, this section guides the user step by step through running the selected experiments, post-processing the model outputs, downloading the reference data and visualising the model outputs with Metview. A catalogue from the prepared figures is also included. The input data and the namelists needed for the model runs, the scripts for the MARS retrieves of the re-analyses, the Metview macros for visualization and the output figures are available for download on the ECMWF download server.

- download from download.ecmwf.int/openifs/evalution

Storm Xavier

On the 5 December 2013 the cyclone swept from Scotland, over the North Sea and hit Denmark, Germany and Sweden. Problems were caused both by the wind and the following storm surge. The surged reached 6 metres in Hamburg for example and was the highest along the England east-coast for 60 years. In the aftermaths of the cyclone a blizzard hit Sweden. The cyclone was presented in the forecasts 8-9 days before the event and the forecasts indicated the very strong winds 3-4 days in advance.

Several OpenIFS experiments have been conducted for this case with the aim to test the effect of starting date and forecast length, initial condition as well as spatial resolution to the forecast quality. The details of experiments are summarized in Table 2.

Table 2: Settings of the experiments achieved for Storm Xavier.

Post-processing step

- how to prepare data for plotting

- precipitation.

Metview macros

- where they are, how to set them up .. etc