What is an Anticyclonic Tornado?
An anticyclonic tornado is a tornado that rotates in the opposite direction of most tornadoes in a given hemisphere. In the Northern Hemisphere, where tornadoes usually rotate counterclockwise (cyclonic rotation), an anticyclonic tornado instead spins clockwise. In the Southern Hemisphere, where typical tornadoes rotate clockwise, an anticyclonic tornado rotates counterclockwise.
These tornadoes are uncommon and often form under specific atmospheric conditions, such as within the outer edges of supercell thunderstorms or along boundaries where winds shift direction. They are usually weaker and shorter-lived than their cyclonic counterparts but can still cause significant damage.
How Do Anticyclonic Tornadoes Form?
Anticyclonic tornadoes typically develop in association with:
- Non-supercell thunderstorms: These tornadoes can form in storm environments where local wind patterns create small-scale rotation.
- Supercells with strong rear-flank downdrafts (RFDs): In rare cases, an anticyclonic tornado can form near the RFD of a supercell, often in the storm’s left flank.
- Mesoscale convective systems (MCS): Some anticyclonic tornadoes develop along squall lines or within mesoscale convective vortices (MCVs), particularly in the wake of large storm systems.
Are Anticyclonic Tornadoes Dangerous?
While typically less intense than cyclonic tornadoes, anticyclonic tornadoes can still be destructive. If they reach EF2 or higher on the Enhanced Fujita (EF) Scale, they can cause damage similar to traditional tornadoes, including:
- Roof damage or destruction of buildings.
- Downed trees and power lines.
- Flying debris, posing risks to people and vehicles.
Because they are rare, meteorologists carefully study them to understand their formation and potential threats better.