A “supercell thunderstorm” has struck Morecambe Bay, compounding travel disruptions persisting due to Storm Gerrit. This weather phenomenon, as detailed by the Met Office, occurs when a thunderstorm is supplied with warm, humid air, initiating rotation.
The Met Office cautioned about heavy rain, hail, frequent lightning, and gusty winds, linking tornado formation typically to these significant thunderstorms referred to as supercells. Notably, an overnight “localised tornado” swept through Greater Manchester.
The storm severely impacted travel networks, including ScotRail, LNER, and Avanti West Coast, while leaving numerous homes without power. Scotland faced the brunt of high winds, heavy rain, and snow, causing damage to electricity networks and leading to train route cancellations due to fallen trees and debris disrupting power lines.
The Met Office confirmed the crossing of a ‘supercell thunderstorm’ across parts of the UK, bringing forth heavy rain, hail, and lightning, with reports suggesting ground vibrations and flickering lights. But what distinguishes a supercell thunderstorm?
Supercells, although less frequent, are notorious for wreaking havoc, generating damaging winds, large hail, and occasionally violent tornadoes. These storms originate from a rotating storm, typically two to six miles in diameter, creating a strong upward draft known as a mesocyclone.
The mesocyclone draws warm, humid air upwards while forcing down cool, dry air, generating powerful winds and sometimes resulting in golf-ball-sized hail. This cycle of warm and cold air sustains the storm, enabling it to persist longer than regular thunderstorms.
Supercells form when atmospheric winds induce turbulent weather, leading the storm to tip and begin spinning vertically. At ground level, supercells manifest as tall, anvil-shaped clouds, often spawning tornadoes at their base.
Explaining the mechanism, a Met Office spokesperson highlighted, “Strong wind shear induces horizontal spin, which the strong updraft then tilts into a vertical axis, much like a merry-go-round’s rotation. Thunderstorms exhibiting continual and profound rotation earn the title ‘supercells.'”