Volcanic Ash Forecasting

• Once an eruption has occurred, the London VAAC initiates a run of the NAME atmospheric dispersion model, a modified version of the Met Office Nuclear Accident Model to forecast the behaviour and trajectory of the volcanic ash plume.
• The London VAAC forecaster provides the location, start time, release height and the top and bottom of the plume (if known) and the model is then run which takes about 15 minutes to complete.
• Output from this model is in a map-based graphical format, and can detail expected ash concentrations over a large region for up to 10 days after the initial volcanic activity.
• The forecaster then prepares the volcanic ash advisory message with the expected positions of the ash plume for up to 24 hours ahead.

Graphical output of the spread of a potential plume is also produced automatically each day for the Icelandic authorities. This is in order that the Icelandic Air Traffic Management authorities are aware of the general wind flow and contingency routes that might have to be deployed before an actual eruption takes place.

Example output from a daily run of the NAME model for Mt. Katla, Iceland

The Met Office has developed two products for the London VAAC that use satellite data to detect and track volcanic ash clouds.

• The Volcanic Ash Detection Tool uses the brightness temperature difference between two spectral channels to detect, monitor and track the movement of volcanic ash.
• The Volcanic Eruption Detection System uses a shape-matching technique to produce an automated alert that a suspected volcanic eruption cloud has been detected.