Have you ever wondered how BBC Weather produce TV forecasts and what steps are required to transform a computer model weather forecast into the broadcast you see on television?
A TV forecast using the latest weather data
BBC Weather forecasters are equipped with computer-based weather information displays linked directly to the super-computers at Met Office HQ in Exeter.
These powerful computer forecast models take in data from around the world continuously and then simulate the world's atmosphere mathematically, from sea-level to the upper atmosphere, and predict what is going to happen.
Latest weather data
BBC forecasters therefore have access to up-to-date information arriving by computer, as well as by fax and email. They interpret this using their skills and experience in meteorology. In consultation with the Met Office chief forecasters, they select the details they wish to use to support the weather story for that day.
The BBC production team work with the forecasters to make sure that the editorial line 'fits' with the BBC's output for the day, and is consistent across all output, whether on television, radio or the website. They also help the forecaster to concentrate on the meteorology by managing the operational, scheduling, data and graphics issues of the day.
Data arrives regularly from the Met Office for the next five days forecast for pressure, temperature, rainfall, cloud cover. This data is processed by the 'Weatherscape XT' graphics system, which creates the graphics seen on television and website forecasts. In addition, satellite pictures for every continent, and hourly satellite images for the UK provide observational information. Half-hourly radar rainfall charts are also drawn up and forecasters can see where the rain is falling and compare this against what the computer forecast models are predicting will happen next.
Weather forecast graphics
The state-of-the-art graphics system uses virtual reality technology to present constantly updated weather data, which means real time forecasting. It allows forecasters to put together a the sequence of charts and other graphics which will give the audience the clearest weather forecast.
The graphics can include still or animated images, video clips, live weather cameras and text charts. They can be in or out of vision, and weather bulletins are customised for different channels and output such as the website or interactive TV.
The solo operation continues in the studio where the forecasters switch on the lights and put in their ear-piece so that they can listen to the programme before their broadcast and to any last-minute instructions from the director in the network control room.
Presenting in front of blue screen
The TV studios, designed for digital broadcasting and widescreen technology, incorporate a device which, at the touch of a button, adjusts the height of the camera, lighting configuration and microphone level to suit each of the presenters individually.
Broadcasting the forecast bulletin
The forecaster stands in front of a translucent screen on which is projected a faint image of the graphics. This gives the forecaster an idea of where to point. The back of the screen is flooded with blue or green light and an electronic system, known as Colour Separation Overlay (CSO), causes any area where the camera detects blue or green to be replaced by a 'clean feed' of the charts from the computer.
The forecaster can then call up a sequence of graphics at using a remote clicker. The forecasters can't dress in blue or green clothing as this would cause them to merge with the graphics.
Monitors next to the camera show the output of the graphics computer and the output of the studio. In front of the camera is an autocue screen, which shows the forecaster an image of themselves standing in front of the graphics - this is the image the audience will see. Superimposed on to this image is a countdown clock.
The forecaster starts their forecast when they receive their cue from the programme or network director and stops when the countdown clock reaches zero.