Analysis

The Global Telecommunication System (GTS) was set up to transfer weather observations (and forecasts) around the world. The international circuit comprises a sequence of high-speed computer-to-computer links, using communication satellites as well as land lines.

The Telecommunications Centre at Met Office Headquarters in Exeter has the role of passing data between Washington and continental Europe via Paris and Offenbach. It also collects observations from the UK and transmits them around the world via the GTS. A complete set of observations from the UK is available around ten minutes past the hour of observation.

The observations taken from the GTS are stored on computer and are analysed in two different ways.

• The observations at a specific time are plotted on a chart and an analysis is produced by the computer. This involves isobars (lines of constant pressure) being drawn, which allows depressions and anticyclones to be identified. The analysis may be modified by the forecasters and fronts are added (with the aid of satellite and radar information) in order to understand what is going on in the atmosphere.
• The observations are used to define the starting conditions of the atmosphere for a computer forecast which can go as far as ten days ahead.