Using global satellite imagery and data, Fromm suspected the large cloud – now appearing over the middle of the country – was a pyrocumulonimbus, or "pyroCb". It was a first for Western Europe since records began, although it would take months longer to confirm it with the help of Portuguese meteorologists. A pyroCb is a thunderstorm generated by fire that creates its own positive feedback loops, including winds, lightning and sometimes deadly downdrafts that spread the fire outwards.