The Met Office (originally an abbreviation for Meteorological Office, but now the official name in itself), which has its headquarters at Exeter in Devon, is the United Kingdom's national weather service and a subsidiary of the Ministry of Defence. Part of the Met Office complex in Exeter is the Met Office College, which handles the training for internal personnel and many forecasters from around the world. The current chief executive is John Hirst who replaced Mark Hutchinson on 17 September, 2007.
The development of the electric telegraph in the 1870's led to the more rapid dissemination of warnings and also led to the development of an observational network which could then be used to provide synoptic analyses.
In 1879 the Met Office started providing forecast to Newspapers.
Following the First World War the Met Office later became part of the Air Ministry in 1920. In 1936 the Met Office split with services to the Royal Navy being provided by their own forecasting services.
It currently holds a quasi-governmental role, being required to act commercially but also remaining an executive agency of the Ministry of Defence. A little known branch of the Met Office known as the Mobile Met Unit (MMU) accompany forward units in times of conflict advising the armed forces of the prevailing conditions for battle, particularly the RAF. The Hadley Centre for Climate Prediction and Research is also part of the Met Office.
In 2003 the Met Office moved its headquarters to Exeter, in Devon from its previous location of Bracknell in Berkshire and it has a worldwide presence including a forecasting centre in Aberdeen and offices in Gibraltar and on the Falklands. Other outposts lodge in establishments such as the Joint Centre for Mesoscale Meteorology (JCMM) at University of Reading in Berkshire, the Joint Centre for Hydro-Meteorological Research (JCHMR) site at Wallingford in Oxfordshire and there is also a Met Office presence at many Army and Air Force bases within the UK and abroad. Royal Navy weather forecasts are generally provided by naval officers, not Met Office personnel.
Their main role is to produce forecast models by gathering all the information from satellites in space and observations on earth, then processing it using supercomputers which produce a variety of models, collectively known as the Unified Model. If necessary, forecasters may then make adjustments to the forecasts. This main bulk of data is then passed on to companies who acquire it. In particular, two of the main media companies, the BBC and ITV produce forecasts using the Met Office's data. At the BBC Weather Centre, they are continuously updated on the latest information arriving by computer, or by fax and e-mail. The BBC's new graphics are used on all of their television weather broadcasts, but ITV use animated weather symbols. This is mainly how the public are informed of weather events which may affect day-to-day life.
In the air quality forecasts, the level of pollution is described either as an index (ranging from 1 to 10) or as a banding (low, moderate, high or very high). These levels are based on the health effects of each pollutant as shown just below.
|1–3||Low||Effects are unlikely to be noticed even by individuals who know they are sensitive to air pollutants.|
|4–6||Moderate||Mild effects, unlikely to require action, may be noticed amongst sensitive individuals.|
|7-9||High||Significant effects may be noticed by sensitive individuals and action to avoid or reduce these effects may be needed (e.g. reducing exposure by spending less time in polluted areas outdoors). Asthmatics will find that their 'reliever' inhaler is likely to reverse the effects on the lung.|
|10||Very High||The effects on sensitive individuals described for 'High' levels of pollution may worsen.|
The forecast is produced for a number of different pollutants and their typical health effects are shown in the following table.
|Pollutant||Health Effects at High Level|
| These gases irritate the airways of the lungs, increasing the symptoms|
of those suffering from lung diseases.
|Particulates|| Fine particles can be carried deep into the lungs where they can cause|
inflammation and a worsening of heart and lung diseases
|Year||Computer||Calculations a second||Horizontal Resolution (Global/local)||Number of Vertical levels|
|1959||Ferranti Mercury||3Kflops||(N.A./320 km)||2 levels|
|1965||English Electric KDF9||50Kflops||(N.A./300 km)||3 levels|
|1972||IBM System/360 195||4Mflops||(300 km/100 km)||10 levels|
|1982||CDC Cyber 205||200Mflops||(150 km/75 km)||15 levels|
|1991||Cray Y-MP C90/16||10Gflops||(90 km/17 km)||19 levels|
|1997||Cray T3E 900/1200||430Gflops||(60 km/12km)||38 levels|
|2004||NEC SX-6||2.0Tflops||(40km/4km)||50 levels|
Some stations have limited reporting times, while other report continuously, mainly RAF and Army Air Corps stations where a manned met office is provided for military operations. The "standard" is a once-hourly reporting schedule, but automatic stations can often be "polled" as required, while stations at airfields regularly report twice-hourly, with additional (often frequent in times of bad weather) special reports as necessary to inform airfield authorities of changes to the weather that may affect aviation operations.
Some stations report only CLIMAT data (e.g maximum and minimum temperatures, rainfall totals over a period, etc.) and these are usually recorded at 0900 and 2100 hours daily. Weather reports are often performed by Observers not specifically employed by the Met Office, e.g. Air traffic control staff, Coastguards, University staff, etc.