The animation, produced on 23 May, shows the forecast positions of volcanic ash (total column in units of g/m2) from 20:00 GMT on 21 May to 06:00 on 27 May from the Grímsvötn volcanic eruption. The emission source varies in time and assumes a uniform height profile up to the reported plume heights measured by radar. It is also constrained by total fine ash mass determined by satellite.