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This article is about the weather phenomenon. For other uses, see Tornado (disambiguation).
A tornado in central Oklahoma. The tornado itself is the thin tube reaching from the cloud to the ground. The lower part of this tornado is surrounded by a translucent dust cloud, kicked up by the tornado\'s strong winds at the surface
A tornado is a violently rotating column of air which is in contact with both a cumulonimbus cloud or, in rare cases, a cumulus cloud base and the surface of the earth. Tornadoes come in many sizes but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris.
Most tornadoes have wind speeds of 110 mph(177 km/h) or less, are approximately 250 feet (75 m) across, and travel a few miles (several kilometers) before dissipating. Some attain wind speeds of more than 300 mph (480 km/h), stretch more than a mile (1.6 km) across, and stay on the ground for dozens of miles (more than 100 km). Doppler On Wheels. Center for Severe Weather Research (2006). Retrieved on 2006-12-29.Hallam Nebraska Tornado. Omaha/Valley, NE Weather Forecast Office (2005-10-02). Retrieved on 2006-09-08. Edwards, Roger (2006-04-04). The Online Tornado FAQ. Storm Prediction Center. Retrieved on 2006-09-08.
Although tornadoes have been observed on every continent except Antarctica, most occur in the United States.Perkins, Sid (2002-05-11). Tornado Alley, USA. Science News 296–298. Retrieved on 2006-09-20. They also commonly occur in southern Canada, south-central and eastern Asia, east-central South America, Southern Africa, northwestern and southeast Europe, Italy, western and southeastern Australia, and New Zealand.
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A tornado near Seymour, Texas.
The word "tornado" is an altered form of the Spanish word tronada, which means "thunderstorm". This in turn was taken from the Latin tonare, meaning "to thunder". It most likely reached its present form through a combination of the Spanish tronada and tornar ("to turn"); however, this may be a folk etymology.Harper, Douglas (November 2001). Online Etymology Dictionary. Retrieved on 2006-09-20. (1993) Merriam Webster\'s Collegiate Dictionary, 10th Edition, Springfield, MA: Merriam-Webster, Incorporated. ISBN 0-87779-709-9. Tornadoes are also commonly referred to as twisters.
A multiple-vortex tornado outside of Dallas, Texas on April 2, 1957.
A waterspout near the Florida Keys.
A landspout near North Platte, Nebraska on May 22, 2004.
Dust devil in Johnsonville, South Carolina.
A wedge tornado, nearly a mile wide. This tornado hit Binger, Oklahoma.
A rope tornado in its dissipating stage.
Most tornadoes take on the appearance of a narrow funnel, a few hundred yards (a few hundred meters) across, with a small cloud of debris near the ground. However, tornadoes can appear in many shapes and sizes.
Small, relatively weak landspouts may only be visible as a small swirl of dust on the ground. While the condensation funnel may not extend all the way to the ground, if associated surface winds are greater than 40 mph (64 km/h), the circulation is considered a tornado. Large single-vortex tornadoes can look like large wedges stuck into the ground, and so are known as wedge tornadoes or wedges. A wedge can be so wide that it appears to be a block of dark clouds, wider than the distance from the cloud base to the ground. Even experienced storm observers may not be able to tell the difference between a low-hanging cloud and a wedge tornado from a distance.Edwards, Roger. Wedge Tornado. National Weather Service Storm Prediction Center. Retrieved on 2007-02-28.
Tornadoes in the dissipating stage can resemble narrow tubes or ropes, and often curl or twist into complex shapes. These tornadoes are said to be roping out, or becoming a rope tornado. Multiple-vortex tornadoes can appear as a family of swirls circling a common center, or may be completely obscured by condensation, dust, and debris, appearing to be a single funnel.Edwards, Roger. Rope Tornado. National Weather Service Storm Prediction Center. Retrieved on 2007-02-28.
In addition to these appearances, tornadoes may be obscured completely by rain or dust. These tornadoes are especially dangerous, as even experienced meteorologists might not spot them.
In the United States, on average tornadoes are around 500 feet (150 m) across, and stay on the ground for 5 miles (8 km). Yet, there is an extremely wide range of tornado sizes, even for typical tornadoes. Weak tornadoes, or strong but dissipating tornadoes, can be exceedingly narrow, sometimes only a few feet across. A tornado was once reported to have a damage path only 7 feet (2 m) long. On the other end of the spectrum, wedge tornadoes can have a damage path a mile (1.6 km) wide or more. A tornado that affected Hallam, Nebraska on May 22, 2004 was at one point 2.5 miles (4 km) wide at the ground."Hallam Nebraska Tornado." National Weather Service Weather Forecast Office, Omaha/Valley, NE. November 2, 2005.
In terms of path length, the Tri-State Tornado, which affected parts of Missouri, Illinois, and Indiana on March 18, 1925, was officially on the ground continuously for 219 miles (352 km). Many tornadoes which appear to have path lengths of 100 miles (160 km) or longer are actually a family of tornadoes which have formed in quick succession; however, there is no substantial evidence that this occurred in the case of the Tri-State Tornado.Grazulis, Thomas P (1993 July). Significant Tornadoes 1680–1991. St. Johnsbury, VT: The Tornado Project of Environmental Films. ISBN 1-879362-03-1. In fact, modern reanalysis of the path suggests that the tornado began 15 miles (24 km) further west than previously thought.Doswell, Dr. Charles A, III. The Tri-State Tornado of 18 March 1925 Reanalysis Project (Powerpoint Presentation). Retrieved on 2007-04-07.
Tornadoes can have a wide range of colors, depending on the environment in which they form. Those which form in a dry environment can be nearly invisible, marked only by swirling debris at the base of the funnel. Condensation funnels which pick up little or no debris can be gray to white. While travelling over a body of water as a waterspout, they can turn very white or even blue. Funnels which move slowly, ingesting a lot of debris and dirt, are usually darker, taking on the color of debris. Tornadoes in the Great Plains can turn red because of the reddish tint of the soil, and tornadoes in mountainous areas can travel over snow-covered ground, turning brilliantly white.
Photographs of the Waurika, Oklahoma tornado of May 30, 1976, taken at nearly the same time by two photographers. In the top picture, the tornado is front-lit, with the sun behind the east-facing camera, so the funnel appears nearly white. In the lower image, where the camera is facing the opposite direction, the tornado is back-lit, with the sun behind the clouds.Edwards, Roger. Public Domain Tornado Images. National Severe Storms Laboratory. Retrieved on 2006-10-20.
Lighting conditions are a major factor in the appearance of a tornado. A tornado which is "back-lit" (viewed with the sun behind it) appears very dark. The same tornado, viewed with the sun at the observer\'s back, may appear gray or brilliant white. Tornadoes which occur near the time of sunset can be many different colors, appearing in hues of yellow, orange, and pink.Lloyd, Linda Mercer. (1996). Target: Tornado [Videotape]. Atlanta, Georgia: The Weather Channel Enterprises, Inc..The Tornado Project\'s Terrific, Timeless and Sometimes Trivial Truths about Those Terrifying Twirling Twisters!. The Tornado Project (1999). Retrieved on 2007-03-21.
Dust kicked up by the winds of the parent thunderstorm, heavy rain and hail, and the darkness of night are all factors which can reduce the visibility of tornadoes. Tornadoes occurring in these conditions are especially dangerous, since only weather radar observations, or possibly the sound of an approaching tornado, serve as any warning to those in the storm\'s path. Fortunately most significant tornadoes form under the storm\'s rain-free base, or the area under the thunderstorm\'s updraft, where there is little or no rain. In addition, most tornadoes occur in the late afternoon, when the bright sun can penetrate even the thickest clouds. Also, night-time tornadoes are often illuminated by frequent lightning.
There is mounting evidence, including Doppler On Wheels mobile radar images and eyewitness accounts, that most tornadoes have a clear, calm center with extremely low pressure, akin to the eye of tropical cyclones. This area would be clear (possibly full of dust), have relatively light winds, and be very dark, since the light would be blocked by swirling debris on the outside of the tornado. Lightning is said to be the source of illumination for those who claim to have seen the interior of a tornado.R. Monastersky (1999-05-15). Oklahoma Tornado Sets Wind Record. Science News 308–309. Retrieved on 2006-10-20.Justice, Alonzo A (May 1930). Seeing the Inside of a Tornado (PDF). Monthly Weather Review 205–206. American Meteorological Society. Retrieved on 2006-10-20.Hall, Roy S. (2003). "Inside a Texas Tornado", Tornadoes. Farmington Hills, MI: Greenhaven Press, 59–65. ISBN 0-7377-1473-5.
Tornadoes normally rotate cyclonically in direction (counterclockwise in the northern hemisphere, clockwise in the southern). While large-scale storms always rotate cyclonically due to the Coriolis effect, thunderstorms and tornadoes are so small that the direct influence of Coriolis effect is inconsequential, as indicated by their large Rossby numbers. Supercells and tornadoes rotate cyclonically in numerical simulations even when the Coriolis effect is neglected.Davies-Jones, Robert (October 1984). "Streamwise Vorticity: The Origin of Updraft Rotation in Supercell Storms". Journal of the Atmospheric Sciences 41 (20): 2991–3006. American Meteorological Society. Retrieved on 2007-04-13. Rotunno, Richard; Joseph Klemp (February 1985). "On the Rotation and Propagation of Simulated Supercell Thunderstorms". Journal of the Atmospheric Sciences 42 (3): 271–292. American Meteorological Society. Retrieved on 2007-04-13. Low-level mesocyclones and tornadoes owe their rotation to complex processes within the supercell and ambient environment.Wicker, Louis J.; Robert B. Wilhelmson (August 1995). "Simulation and Analysis of Tornado Development and Decay within a Three-Dimensional Supercell Thunderstorm". Journal of the Atmospheric Sciences 52 (15): 2675–2703. American Meteorological Society. Retrieved on 2007-04-13.
Approximately 1% of tornadoes rotate in an anticyclonic direction. Typically, only landspouts and gustnados rotate anticyclonically, and usually only those which form on the anticyclonic shear side of the descending rear flank downdraft in a cyclonic supercell.Forbes, Greg. weather.com - Blog: The Weather Channel on weather news, hurricanes, tornadoes & meteorology. Retrieved on 2006-12-30. However, on rare occasions, anticyclonic tornadoes form in association with the mesoanticyclone of an anticyclonic supercell, in the same manner as the typical cyclonic tornado, or as a companion tornado—either as a satellite tornado or associated with anticyclonic eddies within a supercell.Monteverdi, John (2003-01-25). Sunnyvale and Los Altos, CA Tornadoes May 4, 1998. Retrieved on 2006-10-20.
Tornadoes emit widely on the acoustics spectrum and the sounds are cased by multiple mechanisms. Various sounds of tornadoes have been reported throughout time, mostly related to familiar sounds for the witness and generally some variation of a whooshing roar. Popularly reported sounds include a freight train, rushing rapids or waterfall, a jet engine from close proximity, or combinations of these. Many tornadoes are not audible from much distance; the nature and propagation distance of the audible sound depends on atmospheric conditions and topography.
The winds of the tornado vortex and of constituent turbulent eddies, as well as airflow interaction with the surface and debris, contribute to the sounds. Funnel clouds also produce sounds. Funnel clouds and small tornadoes are reported as whistling, whining, humming, or the buzzing of innumerable bees or electricity, or more or less harmonic, whereas many tornadoes are reported as a continuous, deep rumbling, or an irregular sound of “noise”.Abdullah, Abdul (April 1966). "The "Musical" Sound Emitted by a Tornado"". Monthly Weather Review 94 (4): 213–220. American Meteorological Society.
Since many tornadoes are audible only in very close proximity, sound is not reliable warning of a tornado. And, any strong, damaging wind, even a severe hail volley or continuous thunder in a thunderstorm may produce a roaring sound.Hoadley, David (March 1983). "Tornado Sound Experiences". Stormtrack 6 (3): 5-9.
An illustration of generation of infrasound in tornadoes by the Earth System Research Laboratory\'s Infrasound Program.
Tornadoes also produce identifiable inaudible infrasonic signatures.Bedard, A. J. (January 2005). "Low-Frequency Atmospheric Acoustic Energy Associated with Vortices Produced by Thunderstorms". Monthly Weather Review 133 (1): 241–263. American Meteorological Society. Unlike audible signatures, tornadic signatures have been isolated; due to the long distance propagation of low-frequency sound, efforts are ongoing to develop tornado prediction and detection devices with additional value in understanding tornado morphology, dynamics, and creation. Tornadoes also produce a detectable seismic signature, and research continues on isolating it and understanding the process.Tatom, Frank; Kevin R. Knupp, and Stanley J. Vitto (February 1995). "Tornado Detection Based on Seismic Signal". Journal of Applied Meteorology 34 (2): 572–582. American Meteorological Society.
Tornadoes emit on the electromagnetic spectrum, for example, with sferics and E-field effects detected.Samaras, Tim M. (October 2004). "A Historical Perspective of In-Situ Observations within Tornado Cores". Preprints of the 22nd Conference on Severe Local Storms, Hyannis, MA: American Meteorological Society. The effects vary, mostly with little observed consistency.
Correlations with patterns of lightning activity have also been observed, but little in way of consistent correlations have been advanced. Tornadic storms do not contain more lightning than other storms, and some tornadic cells never contain lightning. More often that not, overall cloud-to-ground (CG) lightning activity decreases as a tornado reaches the surface and returns to the baseline level when the tornado lifts. In many cases, very intense tornadoes and thunderstorms exhibit an increased and anomalous dominance in positive polarity CG discharges.Perez, Antony H.; Louis J. Wicker, and Richard E. Orville (September 1997). "Characteristics of Cloud-to-Ground Lightning Associated with Violent Tornadoes". Weather and Forecasting 12 (3): 428-437. Electromagnetics and lightning have little to nothing to do directly with what drives tornadoes (tornadoes are basically a thermodynamic phenomenon), though there are likely connections with the storm and environment affecting both phenomena.
Luminosity has been reported in the past, and is probably due to misidentification of external light sources such as lightning, city lights, and power flashes from broken lines, as internal sources are now uncommonly reported and are not known to ever been recorded.
In addition to winds, tornadoes also exhibit changes in atmospheric variables such as temperature, moisture, and pressure. For example, on June 24, 2003 near Manchester, South Dakota, a probe measured a 100 mbar (hPa) (2.95 inHg) pressure deficit. The pressure dropped gradually as the vortex approached then dropped extremely rapidly to 850 mbar (hPa) (25.10 inHg) in the core of the violent tornado before rising rapidly as the vortex moved away, resulting in a V-shape pressure trace. Temperature tends to decrease and moisture content to increase in the immediate vicinity of a tornado.Lee, Julian J.; Timothy P. Samaras, Carl R. Young (October 2004). "Pressure Measurements at the ground in an F-4 tornado". Preprints of the 22nd Conference on Severe Local Storms, Hyannis, Massachusetts: American Meteorological Society.
A sequence of images showing the birth of a tornado. First, the rotating cloud base lowers. This lowering becomes a funnel, which continues descending while winds build near the surface, kicking up dust and other debris. Finally, the visible funnel extends to the ground, and the tornado begins causing major damage. This tornado, near Dimmitt, Texas, was one of the best-observed violent tornadoes in history.
Tornadoes often develop from a class of thunderstorms known as supercells. Supercells contain mesocyclones, an area of organized rotation a few miles up in the atmosphere, usually 1–6 miles (2–10 km) across. Most intense tornadoes (EF3 to EF5 on the Enhanced Fujita Scale) develop from supercells. In addition to tornadoes, very heavy rain, frequent lightning, strong wind gusts, and hail are common in such storms.
Most tornadoes from supercells follow a recognizable life cycle. That begins when increasing rainfall drags with it an area of quickly descending air known as the rear flank downdraft (RFD). This downdraft accelerates as it approaches the ground, and drags the supercell\'s rotating mesocyclone towards the ground with it.
As the mesocyclone approaches the ground, a visible condensation funnel appears to descend from the base of the storm, often from a rotating wall cloud. As the funnel descends, the RFD also reaches the ground, creating a gust front that can cause damage a good distance from the tornado. Usually, the funnel cloud becomes a tornado within minutes of the RFD reaching the ground.
Initially, the tornado has a good source of warm, moist inflow to power it, so it grows until it reaches the mature stage. This can last anywhere from a few minutes to more than an hour, and during that time a tornado often causes the most damage, and in rare cases can be more than one mile (1.6 km) across. Meanwhile, the RFD, now an area of cool surface winds, begins to wrap around the tornado, cutting off the inflow of warm air which feeds the tornado.
As the RFD completely wraps around and chokes off the tornado\'s air supply, the vortex begins to weaken, and become thin and rope-like. This is the dissipating stage; often lasting no more than a few minutes, after which the tornado fizzles. During this stage the shape of the tornado becomes highly influenced by the winds of the parent storm, and can be blown into fantastic patterns.
As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the inflow powering it. In particularly intense supercells tornadoes can develop cyclically. As the first mesocyclone and associated tornado dissipate, the storm\'s inflow may be concentrated into a new area closer to the center of the storm. If a new mesocyclone develops, the cycle may start again, producing one or more new tornadoes. Occasionally, the old (occluded) mesocyclone and the new mesocyclone produce a tornado at the same time.
Though this is a widely-accepted theory for how most tornadoes form, live, and die, it does not explain the formation of smaller tornadoes, such as landspouts, long-lived tornadoes, or tornadoes with multiple vortices. These each have different mechanisms which influence their development—however, most tornadoes follow a pattern similar to this one. Markowski, Straka, and Rasmussen (2002-10-14). Tornadogenesis Resulting from the Transport of Circulation by a Downdraft: Idealized Numerical Simulations. Journal of the Atmospheric Sciences: Vol. 60, No. 6 28. Retrieved on 2006-09-13.
An example of EF1 damage. Here, the roof has been substantially damaged, and the garage door blown outwards, but the walls and supporting structures are still intact.
The Fujita scale and the Enhanced Fujita Scale rate tornadoes by damage caused. The Enhanced Fujita Scale was an upgrade to the older Fujita scale, with engineered (by expert elicitation) wind estimates and better damage descriptions, but was designed so that a tornado rated on the Fujita scale would receive the same numerical rating. An EF0 tornado will likely damage trees but not substantial structures, whereas an EF5 tornado can rip buildings off their foundations leaving them bare and even deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler radar data, photogrammetry, and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and award a rating.
Tornadoes vary in intensity regardless of shape, size, and location, though strong tornadoes are typically larger than weak tornadoes. The association with track length and duration also varies, although longer track tornadoes tend to be stronger. Brooks, Harold E. (2004-04-01). On the Relationship of Tornado Path Length and Width to Intensity. Weather and Forecasting: Vol. 19, No. 2 310–319. Retrieved on 2007-04-06. In the case of violent tornadoes, only a small portion of the path is of violent intensity, most of the higher intensity from subvortices.
In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. The rate of occurrence drops off quickly with increasing strength—less than 1% are violent tornadoes, stronger than EF4, T8.Edwards, Moller, Purpura et al (2005). Basic Spotters’ Field Guide (PDF). US Department of Commerce, National Weather Service. Retrieved on 2006-11-01.
Outside the United States, areas in south-central Asia, and perhaps portions of southeastern South America and southern Africa, violent tornadoes are extremely rare. This is apparently mostly due to the lesser number of tornadoes overall, as research shows that tornado intensity distributions are fairly similar worldwide. A few significant tornadoes occur annually in Europe, Asia, southern Africa, and southeastern South America, respectively. Dotzek, Nikolai, Jürgen Grieser, Harold E. Brooks (2003-03-01). Statistical modeling of tornado intensity distributions (PDF). Atmospheric Research: Vol. 67–68 163–187. Retrieved on 2007-04-06.
Intense tornado activity in the United States. The darker-colored areas denote the area commonly referred to as Tornado Alley.
The United States has the most tornadoes of any country, about four times more than estimated in all of Europe, not including waterspouts.Dr. Nikolai Dotzek (March 2003). "An updated estimate of tornado occurrence in Europe" (PDF). Atmospheric Research. Retrieved on 2007-03-11. This is mostly due to the unique geography of the continent. North America is a relatively large continent that extends from the tropical south into arctic areas, and has no major east-west mountain range to block air flow between these two areas. In the middle latitudes, where most tornadoes of the world occur, the Rocky Mountains block moisture and atmospheric flow, allowing drier air at mid-levels of the troposphere, and causing cyclogenesis downstream to the east of the mountains. The desert Southwest also feeds drier air and the dry line, while the Gulf of Mexico fuels abundant low-level moisture. This unique topography allows for many collisions of warm and cold air, the conditions that breed strong, long-lived storms many times a year. A large portion of these tornadoes form in an area of the central United States known as Tornado Alley. This area extends into Canada, particularly Ontario and the Prairie Provinces. Strong tornadoes also occasionally occur in northern Mexico.
The United States averages about 1,200 tornadoes per year. The Netherlands has the highest average number of recorded tornadoes per area of any country (more than 20, or 0.0013 per sq mi (0.00048 per km²), annually), followed by the UK (around 33, or 0.00035 per sq mi (0.00013 per km²), per year), but most are small and cause minor damage. In absolute number of events, ignoring area, the UK experiences more tornadoes than any other European country, excluding waterspouts.
Bangladesh and surrounding areas of eastern India suffer from tornadoes of equal severity to those in the US, and occurring more frequently than anywhere else in the world, but such events are under-reported due to the scarcity of media coverage in third-world countries. Tornados kill about 179 people per year in Bangladesh, many more than in the US. This is due to high population density, poor quality of construction, lack of tornado safety knowledge, and other factors.Paul, Bhuiyan (2004). The April 2004 Tornado in North-Central Bangladesh: A Case for Introducing Tornado Forecasting and Warning Systems. Retrieved on 2006-08-17. Other areas of the world that have frequent tornadoes include South Africa, parts of Argentina, Paraguay, and southern Brazil, as well as portions of Europe, Australia and New Zealand, and far eastern Asia.Encyclopædia Britannica. Tornado: Global occurrence. Retrieved on 2007-03-21.
Tornadoes are most common in spring and least common in winter. Since autumn and spring are transitional periods (warm to cool and vice versa) there are more chances of cooler air meeting with warmer air, resulting in thunderstorms. Tornadoes can also be caused by landfalling tropical cyclones, which tend to occur in the late summer and autumn. But favorable conditions can occur at any time of the year.
Tornado occurrence is highly dependent on the time of day, because of solar heating.Kelly, Schaefer, McNulty, et al. (1978-04-10). An Augmented Tornado Climatology (PDF). Monthly Weather Review 12. Retrieved on 2006-09-13. Worldwide, most tornadoes occur in the late afternoon, between 3 and 7 pm local time, with a peak near 5 pm.Tornado: Diurnal patterns. Encyclopædia Britannica Online pg. 6 (2007). Retrieved on 2007-02-27.Holzer, A. M. (2000). "Tornado Climatology of Austria". Atmospheric Research (56): 203–211. Retrieved on 2007-02-27. Dotzek, Nikolai (2000-05-16). "Tornadoes in Germany" (PDF). Atmospheric Research. Retrieved on 2007-02-27. South African Tornadoes. South African Weather Service (2003). Retrieved on 2007-05-21.Finch, Jonathan D.; Dewan, Ashraf M. Bangladesh Tornado Climatology. Retrieved on 2007-02-27. However, destructive tornadoes can occur at any time of day. The Gainesville Tornado of 1936, one of the deadliest tornadoes in history, occurred at 8:30 am local time.
Associations to various climate and environmental trends exist. For example, an increase in the sea surface temperature of source region (e.g. Gulf of Mexico and Mediterranean Sea) increases moisture content, potentially fueling an increase in severe weather and tornado activity, particularly in the cool season.Edwards, Roger; Steven J. Weiss (Feb 1996). "Comparisons between Gulf of Mexico Sea Surface Temperature Anomalies and Southern U.S. Severe Thunderstorm Frequency in the Cool Season". 18th Conference on Severe Local Storms, San Francisco, CA: American Meteorological Society.
Although insufficient support exists to make conclusions, evidence does suggest that the Southern Oscillation is weakly correlated with some changes in tornado activity; which vary by season and region as well as whether the ENSO phase is that of El Niño or La Niña.Cook, Ashton Robinson; Joseph T. Schaefer (2008-01-22). "The Relation of El Nino Southern Oscillation (ENSO) to Winter Tornado Outbreaks". 19th Conference on Probability and Statistics, New Orleans, LA: American Meteorological Society.
Climatic shifts affect tornadoes via teleconnections in shifting the jet stream and the larger weather patterns. The climate-tornado link is confounded by the forces affecting larger patterns and by the local, nuanced nature of tornadoes. Although it is reasonable that the climate change phenomenon of global warming may affect tornado activity, any such effect is not yet identifiable due to the complexity, local nature of the storms, and database quality issues. Any effect would vary by region.Solomon, Susan; et al (2007). Climate Change 2007 - The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK and New York, USA: Cambridge University Press for the Intergovernmental Panel on Climate Change. ISBN 9780521880091.
Probabilistic maps issued by the Storm Prediction Center during the heart of the April 6-8, 2006 Tornado Outbreak. The top map indicates the risk of general severe weather (including large hail, damaging winds, and tornadoes), while the bottom map specifically shows the percent risk of a tornado forming within 25 miles (40 km) of any point within the enclosed area. The hashed area on the bottom map indicates a 10% or greater risk of an F2 or stronger tornado forming within 25 miles (40 km) of a point.
Weather forecasting is handled regionally by many national and international agencies. For the most part, they are also in charge of the prediction of conditions conducive to tornado development.
Severe thunderstorm warnings are provided to Australia by the Bureau of Meteorology. The country is in the middle of an upgrade to Doppler radar systems, with their first benchmark of installing six new radars reached in July 2006.Severe Thunderstorm Warning Service in NSW and the ACT. Australian Government Bureau of Meteorology (2006). Retrieved on 2006-10-25.
The European Union founded a project in 2002 called the European Severe Storms virtual Laboratory, or ESSL, which is meant to fully document tornado occurrence across the continent. The ESTOFEX (European Storm Forecast Experiment) arm of the project also issues one day forecasts for severe weather likelihood.European Severe Weather Database. European Severe Storms Laboratory. Retrieved on 2006-10-25. In Germany, Austria, and Switzerland, an organization known as TorDACH collects information regarding tornadoes, waterspouts, and downbursts from Germany, Austria, and Switzerland. A secondary goal is collect all severe weather information. This project is meant to fully document severe weather activity in these three countries.TorDACH Homepage. TorDACH. Retrieved on 2006-10-25.
In the United Kingdom, the Tornado and Storm Research Organisation (TORRO) makes experimental predictions. The Met Office provides official forecasts for the UK.
In the United States, generalized severe weather predictions are issued by the Storm Prediction Center, based in Norman, Oklahoma. For the next one, two, and three days, respectively, they will issue categorical and probabilistic forecasts of severe weather, including tornadoes. There is also a more general forecast issued for the four to eight day period. Just prior to the expected onset of an organized severe weather threat, SPC issues severe thunderstorm and tornado watches, in collaboration with local National Weather Service offices. Warnings are issued by local National Weather Service offices when a severe thunderstorm or tornado is occurring or imminent.
In Japan, predictions and study of tornadoes in Japan are handled by the Japan Meteorological Agency. In Canada, weather forecasts and warnings, including tornadoes, are produced by the Meteorological Service of Canada, a division of Environment Canada.
A Doppler radar image indicating the likely presence of a tornado over DeLand, Florida. Green colors indicate areas where the precipitation is moving towards the r
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