Every important tornado-related term, from basic weather vocabulary to advanced meteorology - defined clearly and organized alphabetically. Use this glossary while reading other tornado content.
Anticyclonic
Rotating opposite to the Northern Hemisphere norm - clockwise. About 5% of tornadoes are anticyclonic.
Beaver Tail
A flat, elongated cloud extending east from a wall cloud, indicating strong low-level inflow into a supercell.
Bow Echo
A crescent-shaped or bow-shaped line of thunderstorms on radar, often associated with damaging straight-line winds. Different from a supercell.
CAPE (Convective Available Potential Energy)
A measure of atmospheric energy available for updrafts. Higher CAPE = more potential for severe storms.
Cyclone
Any large rotating weather system with low pressure at its center. Includes hurricanes and tornadoes as sub-types.
Cyclonic
Rotating in the direction of the Earth's rotation - counter-clockwise in the Northern Hemisphere. About 95% of tornadoes.
Debris Cloud
Cloud of dust and debris kicked up by a tornado - indicates the tornado has touched ground even when the funnel isn't visible.
Derecho
A long-lived, widespread straight-line windstorm from a squall line. 250+ mile path. Different from a tornado.
Dixie Alley
The Deep South tornado region: Mississippi, Alabama, Louisiana, Arkansas, Tennessee, Georgia. Deadlier per tornado than Tornado Alley. Details →
Doppler Radar
Radar that measures the motion of precipitation and rotation of storms. Essential for tornado detection.
Dryline
A boundary between dry desert air and moist Gulf air over Texas, Oklahoma, and Kansas. A major tornado trigger during spring.
EF Scale (Enhanced Fujita Scale)
The system used since 2007 to rate tornadoes based on damage. Runs from EF0 (65-85 mph) to EF5 (200+ mph). Full explanation →
Funnel Cloud
A rotating funnel extending down from a wall cloud but NOT touching the ground. Becomes a tornado when it reaches the ground.
Fujita Scale (F Scale)
The original tornado intensity scale, 1971-2007. Replaced by the EF Scale. Ran from F0 to F5. Details →
Ground Scouring
Grass, topsoil, and asphalt stripped from the ground by extremely violent tornado winds. A key EF5 damage indicator.
Gustnado
A small, ground-based vortex formed at the leading edge of a thunderstorm's outflow. Not a true tornado. Usually weak.
Hodograph
A meteorological diagram showing wind speed and direction at various altitudes. Used to assess tornado potential.
HP Supercell
High-precipitation supercell. A rotating thunderstorm with heavy rain that can obscure the tornado. Common in Dixie Alley. Very dangerous.
Landspout
A weak tornado forming from the ground up, without a supercell. Similar to a waterspout but over land.
LP Supercell
Low-precipitation supercell. Highly visible with little rain. Common in West Texas and Colorado. Photogenic but not always tornado-producing.
Mesocyclone
The rotating updraft inside a supercell, typically 2-6 miles wide. Produces virtually all violent tornadoes. Details →
Multi-Vortex Tornado
A tornado containing multiple smaller sub-vortices rotating within the parent circulation. Details →
NEXRAD
Next-Generation Weather Radar. The US national Doppler radar network deployed in the 1990s.
Nocturnal Tornado
A tornado occurring at night. 2.5x more likely to kill than daytime tornadoes. Details →
NOAA Weather Radio
A dedicated radio that receives NWS weather alerts. Essential for tornado warnings. Recommendations →
NWS (National Weather Service)
The US federal agency responsible for weather forecasts and warnings.
Outbreak
Six or more tornadoes from a single weather system in a 24-hour period. Details →
Overshooting Top
A dome-shaped protrusion above a thunderstorm's anvil, indicating a very strong updraft.
PDS Watch (Particularly Dangerous Situation)
An enhanced tornado watch issued when violent tornadoes are highly likely.
Rain-Wrapped Tornado
A tornado obscured by heavy precipitation. Common in Dixie Alley and hurricane-spawned tornadoes. Extremely dangerous.
Rear-Flank Downdraft (RFD)
A downdraft that wraps around the mesocyclone. Often involved in tornado genesis.
Rope Tornado
A thin, twisting tornado - often in the early or dissipating stages.
Skywarn
The NWS's volunteer storm spotter network. Trained citizens who report severe weather.
Squall Line
A long line of thunderstorms, often producing straight-line winds. Some produce embedded tornadoes.
Storm Prediction Center (SPC)
NOAA facility in Norman, OK responsible for national tornado watches and severe weather outlooks.
Storm Spotter
A trained observer who reports severe weather to the NWS. See Skywarn.
Stovepipe Tornado
A tornado that is roughly the same width from top to bottom - cylindrical shape.
Sub-Vortex
A smaller, intense vortex rotating within a multi-vortex tornado.
Supercell
A thunderstorm with a rotating updraft (mesocyclone). Produces nearly all violent tornadoes.
Tornadic Waterspout
A supercell-formed tornado over water. Can move onshore as a land tornado.
Tornado
A violently rotating column of air extending from a thunderstorm to the ground.
Tornado Alley
The central US region with the highest tornado frequency. Texas, Oklahoma, Kansas, Nebraska. Details →
Tornado Emergency
The NWS's highest tornado warning level. A confirmed violent tornado is approaching a populated area. Details →
Tornado Warning
Notification that a tornado has been detected or is imminent in your area. Take shelter immediately.
Tornado Watch
Notification that conditions are favorable for tornado development. Stay alert but no immediate action needed.
TVS (Tornado Vortex Signature)
A radar signature indicating a small area of intense rotation - often a tornado.
Updraft
A powerful rising column of warm, moist air inside a thunderstorm.
Wall Cloud
A lowered, rotating segment of a supercell's cloud base. Precedes tornadoes by 10-30 minutes. Details →
Waterspout
A tornado-like vortex over water. Can be tornadic (formed from supercells) or fair-weather (weaker, forms from surface heating).
WEA (Wireless Emergency Alerts)
Automatic phone alerts for tornado warnings and other emergencies. Enable in phone settings.
Wedge Tornado
A tornado wider than it is tall - looks like a black rectangle. Usually EF3+.
Wind Shear
Change in wind speed or direction with altitude. Essential for supercell formation.