Balloons that help balloonists

It is somewhat ironic that when predicting the weather for hot air balloon flights, the Met Office uses another type of balloon, commonly known as the weather balloon.

These helium filled balloons are fitted with a radiosonde, a unit that measures atmospheric conditions and relays them to a fixed receiver on the ground.

There is an average of 4 to 5 weather balloons launched from each of the hundreds of weather stations UK wide, and consist of a balloon, parachute and various instruments used to measure temperature and humidity.

Initially the weather balloons were filled with hydrogen, but this is highly flammable and the Met Office now uses helium which is much less hazardous.

When a weather balloon is launched it is tracked by radar and wind speed and direction is measured as it rises through the atmosphere. The balloon expands as it rises and when it reaches about 7000 feet the pressure bursts the balloon and the instruments float back down to the ground on the end of the parachute.

The data is then collected, wind speed and direction is calculated and the temperature and humidity are used to determine how much cloud is likely to form throughout the day. This in turn is relayed to the hot air balloon team that will decide if the weather conditions are right for the balloon flight to go ahead.