What is a Mesocyclone?

A mesocyclone is a large, rotating column of air inside a thunderstorm, typically associated with supercell thunderstorms. It is a storm-scale feature that can be 2-6 miles wide and is the source of rotation for a tornado. Detected by Doppler radar, a mesocyclone indicates the potential for severe weather, including large hail, strong winds, and tornadoes.

How a Mesocyclone Forms

Horizontal Rotation: Wind at different altitudes changes speed and direction, creating a horizontal spinning vortex.

Updraft Tilts the Vortex: The strong rising air current (updraft) within a thunderstorm tilts this horizontal vortex into a vertical orientation.

Formation: This tilted, rotating column of air is known as a mesocyclone.

Key Characteristics

Size: Typically 2 to 6 miles (3 to 10 km) in diameter.

Detection: Identified by Doppler weather radar as a signature of storm-scale rotation.

Association with Supercells: A persistent, deep mesocyclone is the defining feature of a supercell thunderstorm.

Significance

Tornado Potential: Mesocyclones are essential for tornado formation, as they provide the rotating updraft necessary for a tornado to develop.

Severe Weather Indicator: The presence of a mesocyclone indicates a storm capable of producing severe weather, and a strong, persistent one may lead to a tornado warning.

Longevity: The rotation within a mesocyclone can allow a thunderstorm to persist and organize for hours, leading to supercells.