About this page
Some sailors prefer to use ECMWF charts, others like the UK output, or that from Offenbach and, increasingly sailors are using GRIB output from the US. Not surprisingly, I get asked, from time to time about the differences between the various forecast centres that issue weather charts. The following may help to clear the air - or make it more foggy
On this page -
- National Met Services
- Met Office Output
- Comparison with other Centres
- How Good is the UK Met Office?
The European Centre for Medium-Range Weather Forecasts is an independent international organisation set up, initially, as a research organisation to develop forecasting in the medium range ie up to about two weeks ahead. Member States are:
Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom.
There are co-operation agreements with:
Bulgaria, Croatia, Czech Republic, Estonia, the former Yugoslav Republic of Macedonia, Hungary, Israel, Latvia, Lithuania, Montenegro, Morocco, Romania, Serbia and Slovakia.
- WMO - World Meteorological Organisation
- EUMETSAT - European Organisation for the Exploitation of Meteorological Satellites
- ACMAD - African Centre of Meteorological Applications for Development
- JRC - Joint Research Centre
- CTBTO - Preparatory Commission for the Comprehensive Nuclear Test-Ban Treaty Organisation
- CLRTAP - Executive Body of the Convention on Long-Range Tran boundary Air Pollution
- ESA - European Space Agency
The Centre has now taken on a more operational role although research is still a vital component. Now, the principal objectives of the Centre are:
- development and operation of global models and data-assimilation systems for the dynamics, thermodynamics and composition of the Earth's fluid envelope and interacting parts of the Earth-system, with a view to:
- preparing forecasts by means of numerical methods;
- providing initial conditions for the forecasts; and
- contributing to monitoring the relevant parts of the Earth-system;
- carrying out scientific and technical research directed towards improving the * quality of these forecasts;
- collection and storage of appropriate data.
ECMWF uses, and continues to develop, a state of the art numerical weather prediction model. Several forecasting suites are running operationally at ECMWF. Of interest to sailors global 10-day forecasts based on 00 and 12 UTC analyses. Charts are available from 1 to 10 days ahead. An interesting facility is to be able to look at previous forecasts verifying at the same time. Remember that consistency between successive forecasts implies that the forecast is on the right lines; vice versa for inconsistency.
These charts are very broad scale, even more so than UK Met Office charts. However, they do provide another "opinion" that sailors find useful for planning purposes.
Several European National Weather Services, the UK, France, Germany and Italy run their own numerical weather prediction models. So does a group of countries known as the HIRLAM group (Scandinavian and Low countries, Iceland, Ireland, and Spain). These centres are more concerned with the next 24 - 48 hours ahead and their models are likely to be optimised for their prime areas of interest.
In some operational weather services, notably the UK, experienced forecasters amend their forecast output subjectively and put fronts onto their forecast charts. This is done partly in the interests of making the charts look realistic and partly to take account of any later information not used by the computer. The forecasters can also look at models from the other centres and may decide that these are giving better guidance than the national model.
The UK runs it global Numerical Weather prediction model 4 times a day. Runs based on 00 and 12 UTC are the main runs with the best data analyses. The runs at 06 and 18 UTC are for updating purposes. The global model uses a grid length of about 17 km. The global model provides forecasts up to 6 days ahead.
Starting with the global model, the Met Office also runs a North Atlantic European model with a 4 km grid length for 48 hours for the area shown in the blue square
The data from this are then used to run a Limited Area Model (LAM) just for the British Isles. This model is run to 36 hours only using a 1.5 km grid.
The ECMWF model is probably the most advanced global model although there may not be much difference between the global models run by other countries. Which model does best on any particular occasion can vary.
Most European countries run meso-scale models. Some, such as the HIRLAM group start with the ECMWF data analysis. Others, primarily the UK and France, start with their own global models. In all cases, detailed analyses are used appropriate to the model scale. Terrestrial and space based data observing systems will be used, sometimes including radar data.
The Met Office is one of only two World Area Forecast Centres (WAFC) - the other is WAFC Washington (NOAA). Since 1984, WAFC London has provided international forecasting services to meet Annex 3 to the ICAO Convention on Civil Aviation.
However, the Met Office, like any other forecast servicre far from perfect. Never rely on one forecast in isolation; always keep updating with the latest information - your own eyes, your own barometer, the latest forecast from the BBC, the Coastguard, the Internet etc etc. Just as you continually check your navigation and pilotage, do the same with the weather. You will never guarantee not to be caught out but you will minimise the risks. On another page, I have place a very brief review of numerical weather prediction and how forecasting has evolved over the ages.