Supercell

Short answer: A supercell is a thunderstorm with a deep, persistent rotating updraft called a mesocyclone.

The National Weather Service (NWS) office in Amarillo says supercells are the least common type of thunderstorm but are especially prone to severe weather, including damaging winds, very large hail and sometimes tornadoes. NOAA's JetStream adds that they cause nearly all significant US tornadoes and most hailstones larger than a golf ball, and that their updrafts can exceed 100 mph (160 km/h). The key ingredient is vertical wind shear, a change in wind speed and direction with height. NWS Amarillo calls moderate to strong shear between the surface and about 20,000 ft the most critical factor. Shear creates horizontal spin, and a strong updraft tilts it upright and stretches it into a rotating column. Shear also tilts the storm, keeping its updraft and downdraft apart so rain-cooled air doesn't choke it off. That's why a supercell can last for hours. Wikipedia gives a typical life of 2–4 hours, sometimes more than 7. Fewer than about 30% produce tornadoes. In a 2017 study, Johannes Dahl showed that simple tilting of the environment's horizontal spin doesn't fully explain the rotation near the ground. Supercells are often classified as classic, low-precipitation and high-precipitation. The footage shows a time-lapse of a towering storm cloud over farm fields.