The maps now tracks the Eyjafjallajokull volcano's ash cloud, as per the Met Office's volcanic ash advisory. The volcano is marked by 4 false NOTAMs. The current ash cloud is delineated in red, the +6 hour forecast in yellow, the +12 hour in dark grey, the +18 hour in light grey. It's updated every 6 hours.
As of 13 May 2010, the current forecast is now included on the RSS and email feeds.