Skip navigation.
Home resources

What is the history behind lettering Bracknell fronts/centres?

(with effect from 1st April, 2000, the scheme whereby letters were assigned to fronts & centres on Bracknell analysis and short-range prognosis charts ceased. The 'tracking' of low pressure centres was also stopped. This was a direct consequence of withdrawal of one of the support rosters within the NMC. "NMC Bracknell" itself 'ceased to be' in 2003, when the Met Office HQ relocated to Exeter.

To avoid re-numbering the FAQ series though, I shall maintain this abbreviated entry for the time being, as there is some historical interest.)

[ the text below, and that for 2B.17, was kindly supplied by Martin Stubbs. ]

As far as is known the practice in the UK Met Office was always to allocate letters to the features on the charts (up to April, 2000) although it is thought that this may have been a numbering system which was started in about 1944 (Lettering of pressure centres, particularly areas of low pressure, may in fact date back to the latter part of the 19th century). In fact the WMO International Analysis Code (still in existence) actually caters for the identification of fronts or systems using a number defined by the code 'NN'. The actual code form is 99NNSS where NN is defined in the WMO Manual on Codes as the identity number of the system or front. Thus analyses prepared at the Central Forecasting Office in Dunstable in the 1940s and early 1950s for example, may well have had identification letters, but when coded a depression with the letter 'A' would be coded as 990100, and possibly referred to on the outstations as Depression '1'. The UK actually coded its analyses and forecasts in three different ways after the Second World War. The coded analysis/prebaratic that went out on the international circuits carried the identifier group 99NNSS (for example, a depression labelled 'A' would have been coded 990100 81297 59346 . . . etc.), the analyses that went out internally within the Met Office converted this to plain language (for example, LA 81297 59346 . . . etc.) and for the marine bulletin to the ships on the North Atlantic the identifier was dropped altogether (81297 59346 . . . etc.).