The European and other Weather Forecast Centres

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. It is supported by 31 States. Its Member States are:

Belgium, Denmark, Germany, Greece, Spain, France, Ireland, Italy, Luxembourg, the Netherlands, Norway, Austria, Portugal, Switzerland, Finland, Sweden, Turkey, United Kingdom .

There are co-operation agreements with:

Czech Republic, Montenegro, Estonia, Croatia, Iceland, Latvia, Lithuania, Hungary, Morocco, Romania, Serbia, Slovenia, Slovakia,

and with:

The World Meteorological Organisation (WMO), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), the African Centre of Meteorological Applications for Development (ACMAD), the Joint Research Centre (JRC), the Preparatory Commission for the Comprehensive Nuclear Test-Ban Treaty Organisation (CTBTO), the Executive Body of the Convention on Long-Range Tran boundary Air Pollution (CLRTAP) and the European Space Agency (ESA)

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:

• the development of numerical methods for medium-range weather forecasting;
• the preparation, on a regular basis, of medium-range weather forecasts for distribution to the meteorological services of the Member States;
• scientific and technical research directed at the improvement of these forecasts;
• collection and storage of appropriate meteorological 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, the main suite is producing daily global analyses for the four main synoptic hours 00, 06, 12 and 18 UTC, and global 10-day forecasts based on 00 and 12 UTC analyses. Charts are available from 3 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.

The operational weather services eg the UK Met Office , Offenbach etc amend their forecast output subjectively and put fronts onto their forecast charts. In other words, they do allow experienced forecasters to modify the computer output. 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 uses a data cut off of about 3 hours ie they start their forecast computer runs at about H + 3 hours; they run them to 6 days ahead twice a day ie from 00 and 12 hours UTC. They also run their models at 06 and 18 hours UTC but only out to 48 hours, All the data, regardless of time and type, and received before the analysis times, are used in a 4-D analysis scheme. The object is to get the best data analysis possible. Weather forecasting, like medical prognoses, depends on a good diagnosis.

In addition, the UK uses earlier cut off times for a UK area very high

resolution model that rune out to 48 hours or so only. (Known as the Meso-scale model)

At about 1215 and 0015 the Met Office issues to the Internet forecast charts (based on the previous 0000 or 1200 UTC data) to 6 days ahead (144 hours from initial data time). These charts are a little difficult to use at first because they are output straight from the computer and contain, in effect, three charts on each page. However, the surface isobars can be seen fairly easily.

ECMWF output is very clear; it is high quality presentationally and scientifically. . Rather more "fussy" charts from the Met Office can be accessed from the USAF in Germany. These are, essentially, computer output with fronts added but no other subjective amendment. Charts that are easier to use are issued on the MetFax service. Similar charts are available also from the German Met service (DWD). Comprehensive lists of weather sites can be found on various web pages; see those sites of particular interest to sailors listed at my Essential Weather Sites for sailors which contains some notes on the various

forms of output. These should be of some help in deciding which to use and what are the differences between the different UK Met Office charts.

The national weather services and the HIRLAM outputs are likely to be as good with some benefits. UK Met Office charts via the USAF base and other sites are also very clear, they show fronts and isobars, are updated twice a day and extend to 5 days ahead.

The UK Met Office and the US National Weather Service, Washington are the two world centres for aviation (and many airlines prefer the UK - even for the southern hemisphere). The Met Office forecasts can be particularly useful during the hurricane season. The US Severe Storm Centre at Miami agrees that the UK Met Office model handles hurricanes better than any other forecasts system. In effect, the UK Met Office is regarded as one of the best world-wide.

That is not to imply that they are perfect. Their predictions are based upon the available data and using the best science available. But, in the final analysis, the

atmosphere is still more complex than the most complex numerical prediction models. Errors can and will occur. Never just take one forecast as gospel. 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.