Gandolf

Gandolf is a thunderstorm warning system, developed in partnership with the UK's Environment Agency, which uses radar, satellite and Met Office model data to predict the development and decay of heavy showers on a 2 km grid.

• A neural network cloud classifier analyses the latest satellite data to pick out convective clouds
  
• Radar and model data are used to produce forecasts of the movement and development or decay of each shower, and the amount of precipitation likely to fall

The forecasting section contains an idealised model of a shower cloud, following five stages of growth. Depending on the speed at which the cloud grows, new showers can be produced from existing developing showers.

In this way, the rainfall characteristics can be preserved to forecast high-intensity rain accurately.

• The model runs every 15 minutes when the showers are detected
  
• Forecasts of instantaneous rain rates are produced in 10-minute steps, out to three hours ahead
  
• Forecasts of the rainfall accumulations over every 15 minutes are also produced for the same period

The main difference between Gandolf and Nimrod is that Gandolf only runs when convective cloud is detected, so there may be differences in the output from both systems.

For further information about working with the Met Office on weather solutions please contact our 24-hour Customer Centre or contact water@metoffice.gov.uk.