Roll clouds are commonly formed along the leading edge of major frontal systems.

Counter-intuitively, as the front approaches forward, the leading cloud-front can be seen to be rising and apparently rolling backwards.

As a horizontally-aligned vortex, the roll cloud, especially over water, has massive potential to act as a temporary storage unit for truly vast quantities of energy but, due to its extreme instability, it has little application in any technology.

Despite their often calm, almost surreal outward appearance, internally each cloud contains extremely dangerous wind shear, with massive updrafts at the leading edge and downdrafts, squalls and virga falling at the rear. As they pass over land, they break into major squalls and often cause flash flooding. The ‘Morning Glory’s’ isolated roll clouds (above) are the only ones that generally break up without causing much rain.