1. Sources of Weather Data How do we measure and predict the weather?

2. Traditional Methods Wherever humans have settled around the world, being able to predict the weather has been an advantage. Many methods have been used throughout the ages to try to predict the weather. An open cone is supposed to mean dry weather and a closed cone indicates damp weather. If the ash tree has leaves first then it will be a summer of rain; if it is the oak tree first then it will be a fine summer. Red sky at night, shepherd's delight / Red sky in the morning, shepherd's warning

3. Modern Methods Most information about the weather is collected now by small automated land-based weather stations around the world. Most modern weather stations are fully automated installations, often powered by solar energy. Readings are relayed to forecasting centres by communications satellites.

4. Weather data from around the world Data comes in from weather balloons, aircraft, ships and buoys. Helium-filled weather balloons are released several times a day in many parts of the world to collect information from the upper atmosphere. These balloons, known as radiosonde devices, carry temperature, pressure and humidity sensors and the observations are transmitted to the ground by radio. Specially- equipped aircraft are used to obtain temperature and humidity readings, and to study the physics of clouds.

5. Loaded with sensitive instruments, and sometimes powered by solar energy, weather buoys either moored, or drifting with ocean currents, provide valuable data for forecasters.

6. Satellites Satellite-derived data helps improve the accuracy of weather forecasts. The information and pictures we can get help us to understand how weather works. They also help us to anticipate weather events better: for example, hurricane warnings.

7. All kinds of different information can be read by satellites. Synthetic aperture radar mapping equipment can penetrate cloud cover. Some images are sensitive to water vapour in the Earth's atmosphere. They can be colour coded to show the differences between clouds, rain and snow. Others measure wave height, sea temperature, even sea-ice thickness. In fact they are so sensitive that they can even measure wind speed.

8. Computers Weather forecasters try to predict what the future weather will be. Hundreds of thousands of pieces of data are collected every day from weather stations, radiosondes, satellites, and observers. To process this amount of information requires ever more powerful computers to perform the millions of calculations per second needed to model and predict the world's ever changing weather. But even the most powerful computer cannot predict the weather more than about five days in advance.

9. The Weather Forecast Looking forward to the future

10. The 1970s Weather Forecast Symbols have been featured on BBC weather charts since the earliest days of television in 1936. The first weathermen had to hand-draw their charts with wax crayons. With the introduction of colour television in 1967, the BBC brought in a new range of symbols which, after discussion with the Met Office, were based on international standards - with triangles for showers, and round dots for rain. Magnetic rubber was employed for the symbols and isobars, which could be stuck to steel wall charts. They could also fall off again!

11. Weather Forecasting Today On Monday, February 18, 1985, magnetic rubber made way for new technology when the most advanced computerised weather display system in the world came into operation using the latest in computer graphics.

12. The Weather Forecast of the Future Early in 2005 the BBC will be using a new style of computer graphics to deliver their forecasts. The new graphics are said to be very much like PS2 or X-box graphics and will be even more detailed than at present.