Glossary of tornado terms
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
A
Advanced Radar Research Center AdvectionAir parcelAmerican Geophysical Union American Meteorological Society Anticipated convection – A convective outlook.Angular momentumAnticycloneAnticyclonic rotationAnticyclonic tornadoAnticyclogenesisArcus cloudAtmosphereB
Baroclinity or baroclinicity – baroclinicBarotropity or barotropicity – barotropicBear's cage – The precipitation that wraps around a mesocyclone, possibly hiding a tornado on the ground.Beaufort scaleBernoulli's principleBlob – Informal term coined by Erik N. Rasmussen for a descending reflectivity core.BoundaryBounded weak echo region Bow echoBRN shearBulk Richardson Number Bulk shear'- ''Buoyancy''
C
Capping inversion Center for Analysis and Prediction of Storms Center for Severe Weather Research Chaser convention – Originally it referred to serendipitous meeting of chasers in the field akin to "chaser convergence", but now it mostly refers to the held annually in the Denver, Colorado area.Cloud tagCluster outbreakCold air funnel – Cold frontCollar cloudColorado lowCool air advection Condensation funnel – The area of a funnel cloud or tornado where cloud has condensed. This is not the same thing as a tornado, which is a vortex of wind.ConfluenceCooperative Institute for Mesoscale Meteorological Studies – Cooperative Institute for Meteorological Satellite Studies Cooperative Institute for Precipitation Systems Cooperative Institute for Research in the Atmosphere ConvectionConvective available potential energy Convective condensation level Convective inhibition Convective instabilityConvective outlookConvective stormConvective storm detectionConvective storm predictionConvective temperature ConvergenceCoreCore flow regionCore punching Corridor outbreakCumulonimbus cloud- Cycloidal marksCyclonic rotationCyclogenesisCyclone An area of cyclonic low pressure, from the scale of an extratropical or tropical cyclone to mesolow to a mesocyclone to a tornadocyclone or even to a tornado. – Historically, used in the US to a tornado.
D
Damage surveyDAPPL database – Short for Damage Area Per Path Length, this is one of three US tornado databases and was maintained by Ted Fujita at the University of Chicago including tornadoes from 1916 to 1992.Debris cloudDeepening lowDeep convectionDeep shearDenver Convergence Vorticity Zone DerechoDescending reflectivity core Dew point Dew point depressionDewpoint surge lineDiffluence – A pattern of wind flow in which air moves outward away from a central axis that is oriented parallel to the general direction of the flow. It is the opposite of confluence.Digging low or digging waveDirect hitDirectional shearDivergenceDoppler on Wheels Doppler weather radarDry convection – A vertical exchange of air without precipitation at the ground.Dry line Dryline bulgeDry punchDry thunderstormDust devilDownburst- ''Downdraft''
E
Earth System Research Laboratories EddyElevated mixed layer Energy-helicity index Energy scale – Wind speed scales proposed by Nikolai Dotzek for application to tornadoes, downbursts, tropical cyclones, other storms and wind in general.Enhanced Fujita scale Enhanced wordingEntrainmentEnvironment and Climate Change CanadaEnvironmental Modeling Center Environmental Research Laboratories Environmental Science Services Administration – The predecessor agency to NOAA.Equivalent potential temperature Extratropical cycloneF
Filling lowFire whirlForecast Decision Training Branch Forecast Systems Laboratory Forward-flank downdraft Fractus cloud FrontFrontogenesisFujita scale- ''Funnel cloud''
G
Gate-to-gate shearGMT Ground truthGust front- ''Gustnado''
H
Handoff – HelicityHigh-precipitation supercell High-pressure area High risk Hook echoHorseshoe vortex- ''Hurricane''
I
In situInflowInflow jetInflow notchInstabilityIntense tornado – A tornado rated F3-F5 or EF3-EF5.- '''Institute for Disaster Research'''
J
Jet max Jet streak- ''Jet stream''
K
KinematicsK-indexL
LandspoutLapse rateLee troughLemon techniqueLevel of free convection Lifted condensation level Lifted index Lifting mechanism Lightning Line echo wave pattern Long track tornado Low-precipitation supercell Low-pressure areaM
MaxitornadoMegasupercellMesoanticyclone – An anticyclonic mesocycloneMesoscale meteorologyMesocycloneMesohighMesolowMesonetMesoscale convective complex Mesoscale convective discussion Mesoscale convective system Mesoscale convective vortex Mesoscale meteorologyMesovorticesMetadataMETARMicroburstMicronet – A weather observation network even denser than a mesonet, such as the Oklahoma City Micronet.Microscale meteorologyMini-supercell – A distinct kind of supercell that is smaller than a typical supercell. See low topped supercell.Mini-tornado – A fallacious term often used in European news media to refer to tornadoes occurring there; even large, strong, and/or long track tornadoes produced by supercells. This is apparently due to the erroneous perception that "real" tornadoes do not occur in Europe.MisocycloneMisoscale meteorology – Mixed air and mixed layerMixing ratioModerate risk Modified Fujita scale – A proposed update in 1992 by Ted Fujita to his original Fujita scale from 1971MoistureMoisture convergence Multicellular thunderstormMultiple-vortex tornado- '''Multivortex mesocyclone'''
N
National Center for Atmospheric Research National Centers for Environmental Prediction National Hurricane Center National Meteorological Center – The predecessor to NCEP.National Oceanic and Atmospheric Administration National Science Foundation National Severe Storms Forecast Center – A predecessor forecasting center to SPC that was located in Kansas City, Missouri.National Severe Storms Laboratory – A NOAA lab in Norman, Oklahoma tasked with researching severe weather.National Tornado Database – The official NOAA record of all known tornadoes within the US from 1950 to present.National Weather Center National Weather Service National Weather Service Training Center National Wind Institute Negative area- ''Negatively tilted''
O
Occluded frontOcclusionOvershooting topOutflow- ''Outflow boundary''
P
Particularly Dangerous Situation Path length – The distance a tornado traveled from formation to decay.Path width – The diameter of the tornado vortex winds capable of causing damage.Pearson scale – A tornado rating scale developed by Allen Pearson differentiating path length and path width to accompany NOAA Fujita scale ratings.PendantPhased array radarPositive areaPotential temperature Power flash – A sudden bright light caused when an overhead power line is severed or especially when a transformer explodes. These can be caused by intense winds from tornadoes or downbursts, but the most prominent example occurred in New York City during Hurricane Sandy when its storm surge flooded a Con Ed power plant.Precipitable waterPrefrontal troughPressure fallsPressure gradientPressure gradient force Pressure systemProbePROFS Pulse-Doppler radar- ''Pulse storm''
Q
R
Radar Operations Center Radius of maximum wind Rain-free base Rankine vortexRear flank downdraft RidgeRoll cloudRemote sensingRope tornadoRossby numberRossby wave- '''Rotation'''
S
Safe roomSatellite tornado – A smaller tornado that orbits a primary tornado associated with the same mesocyclone.Scouring – Term used when soil and dirt is pulled from the surface after a tornado.Scud Severe local storm – A thunderstorm presenting severe characteristics in a localized area.Severe Local Storms Unit – A team of National Weather Service experts tasked with forecasting convective weather. It was eventually included as a unit within the NSSFC.Severe thunderstorm – A hazardous thunderstorm capable of causing injury or damage. The U.S. National Weather Service defines a severe thunderstorm as one producing or greater winds, or larger hail, or producing a funnel cloud or tornado.Shallow convection – Occurs when convective instability exists, but no convection occursShear – Wind shear – Winds aloft, often measured in knots.Shear funnel – Brief, often weak funnel generated by shear in a thunderstorm.Shelf cloud – Generally associated with strong thunderstorms, found along the leading edge. Horizontal and dark in appearance.Shortwave trough – Embedded kink within seen in overall troughing patterns.Significant tornado – A substantial tornado, one that is rated F2-F5 or EF2-EF5. Grazulis also includes F0-F1 tornadoes that cause a fatality in his definition for The Tornado Project database.Significant tornado parameter – Model parameter calculated using shear values, Instability values, and vorticity values.Skipping tornado – Often considered a Multi-vortex tornado.Skywarn – The storm spotting program of the US National Weather Service. Skywarn organizations have also been formed in Europe. The Canadian program is Canwarn.Slight risk Space Science and Engineering Center Speed shearSpin-up – A small, ephemeral vortex. These can refer to tornadoes spawned by quasi-linear convective systems or tropical cyclones, which occasionally become strong and fairly long track. A spin-up may sometimes refer to a landspout or gustnado.Splitting storm Stability indexStacked lowSteam devilStorm chasing – Traveling with the intent to observe tornadoes and other severe weather.Storm interactionStorm mergerStorm relative environmental helicity or storm relative helicity Storm shelterStorm spotting – The observation of severe weather by individuals trained in weather and reporting. Spotters can be stationary or mobile.Storm Data – A National Climatic Data Center publication beginning in 1959 detailing quality controlled tornado and other severe weather summaries as the official NOAA record of such events.Storm Prediction Center – The NWS national guidance center that issues tornado, severe thunderstorm, and wildfire forecasts.Storm scaleStorm Track (magazine) – A science and hobby magazine on storm chasing published from 1977 to 2002.Stovepipe tornado – Storm chaser slang for a large cylindrically shaped tornado resembling a stovepipe.Straight-line windStreamlineStreamwise vorticityStriationsStrong tornado – A tornado rated F2-F3, EF2-EF3, T4-T7, or at least as strong as F2, EF2, T4.SubsidenceSubvortex – A smaller constituent vortex within a tornado.Suction spot – Older term for a subvortex. Supercell Supercell composite parameter – Model parameter calculated using Instability values, Helicity, and effective bulk wind difference.Supertornado – A colloquial term used to refer to a tornado achieving the maximum of some measurement, such as a F5/EF5 tornado.Surface weather analysisSurface weather observationT
Tail – A colloquial term for a tornado; most commonly used in the Southern U.S.Tail cloudTemperatureTerminal Doppler Weather Radar – ThermalThermodynamicsThunderstorm The Thunderstorm ProjectThunderstorm spectrumTilted updraftTornado Tornado Alley – A colloquial term referring to regions where tornadoes are perceived as striking more frequently than other areas. It may also be referred to as a tornado belt, especially when describing smaller areas.Tornado climatology – The study of geographical and temporal distribution of tornadoes and causes thereof.Tornado couplet – A primary cyclonic tornado and secondary anticyclonic tornado pair.Tornado Debris Project Tornado debris signature – A more formal term for a debris ball.Tornado emergency – Enhanced wording used by the U.S. National Weather Service in a tornado warning or severe weather statement when a large, intense tornado is expected to impact a highly populated area.Tornado family – A series of tornadoes spawned by successive mesocyclones of the same supercell thunderstorm in a process known as cyclic tornadogenesis. Multiple such supercells occurring on the same day in a common region results in a corridor outbreak of tornadoes.Tornado fogTornado Force scale Tornado Intercept Project Tornado outbreakTornado outbreak sequenceTornado preparednessThe Tornado Project – A concerted research effort from the 1970s-1990s by Thomas P. Grazulis that compiled tornado information for risk assessment. TP published exhaustive accounts, tabulations, and analysis of all known significant tornadoes in the US from 1680 to 1995, which comprises one of three tornado databases.Tornado pulseTornado rating – A subjective integer value assigned to a tornado differentiating its intensity, typically as a proxy inferred by damage analysis.Tornado roarTornado scaleTornado seasonTornado stagesTornado SymposiumTornado vortex signature Tornado watch – A forecast that atmospheric conditions within a designated area are favorable for significant tornado activity over the next 1–6 hours.Tornado warning – A tornado is occurring or is imminent as one is sighted or is suggested by radar.Tornadocyclone – The parent circulation of a tornado. This may refer to a low-level mesocyclone.Tornadogenesis – The process leading to tornado formation.Tornadolysis – The process leading to tornado decay and death.TORRO TORRO scale – A tornado rating scale developed by Terence Meaden of TORRO classifying tornadoes in the UK from T0-T10 based on intensity.TOTO Transverse rollsTrigger – Tropical cyclone TroughTube – A storm chaser term for a tornado.TurbulenceTwister – A colloquial term for a tornado. Also, a major theatrical film about storm chasing released in 1996.- ''TWISTEX''
U
UpdraftUniversity Corporation for Atmospheric Research- ''UTC''
V
VaultV notchVelocity coupletVent shear or vent windVery long track tornado Violent tornado – A tornado rated F4-F5, EF4-EF5, or T8-T11.VortexVortex breakdownVortex stretchingVORTEX projectsVorticityVorticity maximum- '''Vorticity minimum'''