United Weather Centres West (UWC-West) is a consortium of the four national meteorological and hydrological services (NMHSs) of Denmark, Ireland, the Netherlands, and Iceland (DINI). Common numerical weather prediction (NWP) models have been running operationally since March 2024. The main configuration, DINI-EPS, is an ensemble prediction system based on HARMONIE-AROME, with hourly updates producing a 1+30 member ensemble, forecasting up to 60 hours ahead. The other common NWP configuration is the IG (Iceland–Greenland) domain producing 3-hourly deterministic forecasts for Iceland and Greenland. UWC-West utilises common high-performance computing facilities (HPCF) based in Iceland on the site of the Icelandic NMHS. In addition, high-availability clusters enable UWC-West to run ancillary products and services, including ECMWF's observation processing system SAPP (Scalable Acquisition and Pre-Processing). The observations assimilated by the NWP models are all processed by SAPP and include conventional observations, EMADDC (European Meteorological Aircraft Derived Data Centre) Mode-S aircraft observations, EARS (EUMETSAT ATOVS Retransmission Service) satellite radiances, and supplementary data streams from each of the four partner institutes.
History
SAPP is developed and used operationally by ECMWF. It handles the acquisition, processing, and extraction of meteorological observations of various types and sources into a format useable by NWP models.
In 2014, some NMHSs including Met Éireann, the Irish Meteorological Service, sent a request to ECMWF about the possibility of using SAPP for observation processing. Ireland's existing in-house processing system (Automatic Data Extraction, ADE) had become difficult to maintain given the ever increasing number and type of observations. Following a Member State visit from Enrico Fucile that year, ECMWF agreed to make SAPP available and development work began to replace ADE.
In December 2018, the ECMWF Council approved the Optional Programme supporting the provision of SAPP to participating States in response to interest in the NMHS community. Met Éireann became the first Member State to use SAPP operationally in November 2019. This participation in the Optional Programme has continued in UWC-West, where SAPP is used as the production system for providing observations in BUFR format to the NWP model for data assimilation. The ECMWF SAPP user forum has proved to be a useful source of help and information.
SAPP configuration in UWC-West
UWC-West currently uses the Virtual Machine (VM) version of SAPP v1.2 in a live/live configuration. This means that two VMs run in production mode, allowing a single VM to fail without any loss of data or any intervention required. An off-site VM is installed at Met Éireann, which provides UWC-West with a geo-resilient backup stream of observations should the two production clusters become degraded.
As the NWP model is run hourly, 24 extractions for conventional, satellite, Mode-S, and local observation streams are required daily, with a cutoff of 60 minutes.
The extraction scripts have been modified to perform a spatial check on the observations. Only observations contained within an area incorporating the NWP domains are used (see the figure). This has reduced the extraction time and improved the performance of the system for high-density observations types, such as EMADDC Mode-S aircraft observations.
CI/CD
As part of the requirements for UWC-West, all applications must be 'Continuous Integration and Continuous Deployment' (CI/CD) compliant. When any changes are made to the SAPP repositories, the user may trigger a deployment. This is sent to each of the SAPP virtual machines, where it is installed and SAPP services are restarted.
Future
A development VM has been installed using the latest version of the SAPP VM available from ECMWF, which is v1.3. This is based on Rocky Linux rather than CentOS and uses more up-to-date versions of Python 3 and ecFlow 5. Work is currently ongoing to carry out the customisations required for UWC-West, and it is anticipated that v1.3 will replace both v1.2 machines over the coming months.