The images below show a high-level plume-like cloud extending downwind from Mount Etna for about 200 km to the east.
27 May 2022
11 April 2008
By Jochen Kerkmann (EUMETSAT)
The plume cloud is very cold and has a relatively high reflectance in channel IR3.9r, it appears with a strong yellow colour in the RGB composite (see also High level cloud spreading from Mount Etna (9 March 2007)).
Principally, there are two possible explanations for this plume-like cloud: a) a cloud from a volcanic eruption or b) a mountain wave cloud. The first possibility is unlikely because there are no reports of an eruption of Mount Etna on this day.
Also, there are no signs of volcanic ash or sulfur dioxide (see Met-9 RGB composites) and the cloud temperature of -55 °C speaks more for a wave cloud — a cloud from an eruption of Mount Etna would normally be lower, at 4–5km height, unless the eruption was very strong (which would have been reported on the news). Finally, the synoptic situation on 11 April, with strong westerly winds over Sicily, was favourable for the formation of lee wave clouds over Mount Etna.