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{{short description|Process by which a tornado forms}}
[[Image:Dimmit Sequence.jpg|thumb|200px|right|A sequence of images showing the birth of a [[supercell]]ular tornado. First, the rain-free cloud base lowers as a rotating [[wall cloud]]. This lowering concentrates into a [[funnel cloud]], which continues descending simultaneously as a circulation builds near the surface, kicking up dust and other debris. Finally, the visible funnel extends to the ground, and the tornado begins causing major damage.]]
[[Image:Dimmit Sequence.jpg|thumb|right|A sequence of images showing the birth of a [[supercell]]ular tornado. First, the rain-free cloud base lowers as a rotating [[wall cloud]]. This lowering concentrates into a [[funnel cloud]], which continues descending simultaneously as a circulation builds near the surface, kicking up dust and other debris. Finally, the visible funnel extends to the ground, and the tornado begins causing major damage.]]
[[File:Evolution of a Tornado.jpg|thumb|Composite of eight images shot in sequence as a tornado formed in [[Kansas]] in 2016]]
[[File:Tornado touching down in Falcon, Colorado.jpg|thumb|Tornadogenesis occurring in [[Falcon, Colorado]]. Note the faint dust swirl beneath the funnel cloud.]]
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'''Tornadogenesis''' is the process by which a [[tornado]] forms. There are many types of tornadoes and these vary in methods of formation. Despite ongoing scientific study and high-profile research projects such as [[VORTEX projects|VORTEX]], tornadogenesis is a volatile process and the intricacies of many of the mechanisms of tornado formation are still poorly understood.<ref name="Coffer">{{cite journal |last = Coffer |first = Brice E. |author2 = M. D. Parker |title = Volatility of Tornadogenesis: An Ensemble of Simulated Nontornadic and Tornadic Supercells in VORTEX2 Environments |journal = Mon. Wea. Rev. |volume = 145 |issue = 11|pages = 4605–4625 |date = 2017 |doi = 10.1175/MWR-D-17-0152.1 |bibcode = 2017MWRv..145.4605C |doi-access = free }}</ref><ref name="Trapp & Davies-Jones">{{cite journal |last = Trapp |first = R. Jeffrey |author2 = R. Davies-Jones |title = Tornadogenesis with and without a Dynamic Pipe Effect |journal = J. Atmos. Sci. |volume = 54 |issue = 1|pages = 113–133 |date = 1997 |doi = 10.1175/1520-0469(1997)054<0113:TWAWAD>2.0.CO;2
[[File:Tornado Alley Diagram.svg|thumb|A diagram showing the contributing weather systems to [[Tornado Alley]] in the United States, a loosely-defined area that is prone to tornadoes.]]
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|bibcode = 1997JAtS...54..113T |doi-access = free }}</ref><ref name="RDJ">{{cite conference |first = Robert |last = Davies-Jones |title = Tornadogenesis in supercell storms: What We Know and What We Don't Know |book-title = Symposium on the Challenges of Severe Convective Storms |pages = |publisher = American Meteorological Society |date = 28 January 2006 |location = Atlanta, GA |url = https://ams.confex.com/ams/Annual2006/techprogram/paper_104563.htm |doi = }}</ref>
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'''Tornadogenesis''' is the process by which a [[tornado]] forms. There are many types of tornadoes, varying in methods of formation. Despite ongoing scientific study and high-profile research projects such as [[VORTEX projects|VORTEX]], tornadogenesis is a volatile process and the intricacies of many of the mechanisms of tornado formation are still poorly understood.<ref name="Coffer">{{cite journal |last = Coffer |first = Brice E. |author2 = M. D. Parker |title = Volatility of Tornadogenesis: An Ensemble of Simulated Nontornadic and Tornadic Supercells in VORTEX2 Environments |journal = Mon. Wea. Rev. |volume = 145 |issue = 11|pages = 4605–4625 |date = 2017 |doi = 10.1175/MWR-D-17-0152.1 |bibcode = 2017MWRv..145.4605C |doi-access = free }}</ref><ref name="Trapp & Davies-Jones">{{cite journal |last = Trapp |first = R. Jeffrey |author2 = R. Davies-Jones |title = Tornadogenesis with and without a Dynamic Pipe Effect |journal = J. Atmos. Sci. |volume = 54 |issue = 1|pages = 113–133 |date = 1997 |doi = 10.1175/1520-0469(1997)054<0113:TWAWAD>2.0.CO;2
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|bibcode = 1997JAtS...54..113T |doi-access = free }}</ref><ref name="RDJ">{{cite conference |first = Robert |last = Davies-Jones |title = Tornadogenesis in supercell storms: What We Know and What We Don't Know |book-title = Symposium on the Challenges of Severe Convective Storms |publisher = American Meteorological Society |date = 28 January 2006 |location = Atlanta, GA |url = https://ams.confex.com/ams/Annual2006/techprogram/paper_104563.htm }}</ref>


A tornado is a violently rotating column of air in contact with the surface and a [[cumuliform]] [[cloud base]]. Tornado formation is caused by the stretching of environmental and/or storm-induced [[vorticity]] that tightens it into an intense [[vortex]]. There are various ways this may come about and thus various forms and sub-forms of tornadoes. Although each tornado is unique, most kinds of tornadoes go through a life cycle of formation, maturation, and dissipation.<ref name="French">{{cite journal |last = French |first = Michael M. |author2 = D. M. Kingfield |title = Dissipation Characteristics of Tornadic Vortex Signatures Associated with Long-Duration Tornadoes |journal = J. Appl. Meteorol. Climatol. |volume = 58 |issue = 2|pages = 317–339 |date = 2019 |doi = 10.1175/JAMC-D-18-0187.1 |bibcode = 2019JApMC..58..317F }}</ref> The process by which a tornado dissipates or decays, occasionally conjured as tornadolysis, is of particular interest for study as is tornadogenesis, longevity, and [[tornado intensity|intensity]].
A tornado is a violently rotating column of air in contact with the surface and a [[cumuliform]] [[cloud base]]. Tornado formation is caused by the stretching and aggregating/merging of environmental and/or storm-induced [[vorticity]] that tightens into an intense [[vortex]]. There are various ways this may come about and thus various forms and sub-forms of tornadoes. Although each tornado is unique, most kinds of tornadoes go through a life cycle of formation, maturation, and dissipation.<ref name="French">{{cite journal |last = French |first = Michael M. |author2 = D. M. Kingfield |title = Dissipation Characteristics of Tornadic Vortex Signatures Associated with Long-Duration Tornadoes |journal = J. Appl. Meteorol. Climatol. |volume = 58 |issue = 2|pages = 317–339 |date = 2019 |doi = 10.1175/JAMC-D-18-0187.1 |bibcode = 2019JApMC..58..317F |url = https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1605&context=usdeptcommercepub |doi-access = free }}</ref> The process by which a tornado dissipates or decays, occasionally conjured as tornadolysis, is of particular interest for study as is tornadogenesis, longevity, and [[tornado intensity|intensity]].


== Mesocyclones ==
== Mesocyclones ==
Classical tornadoes are [[supercell]]ular tornadoes, which have a recognizable pattern of formation.<ref name="Advanced Spotter Guide">{{cite web|url=http://www.weather.gov/os/brochures/adv_spotters.pdf |title=Advanced Spotters' Field Guide |accessdate=2006-09-20 |author=Doswell, Moller, Anderson |year=2005 |publisher=[http://www.commerce.gov/ US Department of Commerce] |display-authors=etal |url-status=dead |archiveurl=https://web.archive.org/web/20060823090940/http://www.weather.gov/os/brochures/adv_spotters.pdf |archivedate=2006-08-23 }}</ref> The cycle begins when a strong [[thunderstorm]] develops a rotating [[mesocyclone]] a few miles up in the atmosphere. As rainfall in the storm increases, it 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 rotating mesocyclone towards the ground with it. Storm relative [[Helicity (fluid mechanics)|helicity]] (SRH) has been shown to play a role in tornado development and strength. SRH is horizontal vorticity that is parallel to the [[Inflow (meteorology)|inflow]] of the storm and is tilted upwards when it is taken up by the updraft, thus creating vertical vorticity.
Classical tornadoes are [[supercell]]ular tornadoes, which have a recognizable pattern of formation.<ref name="Advanced Spotter Guide">{{cite web|url=http://www.weather.gov/os/brochures/adv_spotters.pdf |title=Advanced Spotters' Field Guide |accessdate=2006-09-20 |author=Doswell, Moller, Anderson |year=2005 |publisher=[http://www.commerce.gov/ US Department of Commerce] |display-authors=etal |url-status=dead |archive-url=https://web.archive.org/web/20060823090940/http://www.weather.gov/os/brochures/adv_spotters.pdf |archive-date=2006-08-23 }}</ref> The cycle begins when a strong [[thunderstorm]] develops a rotating [[mesocyclone]] a few miles up in the atmosphere. As rainfall in the storm increases, it 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 rotating mesocyclone towards the ground with it. Storm relative [[Helicity (fluid mechanics)|helicity]] (SRH) has been shown to play a role in tornado development and strength. SRH is horizontal vorticity that is parallel to the [[Inflow (meteorology)|inflow]] of the storm and is tilted upwards when it is taken up by the updraft, thus creating vertical vorticity.


As the mesocyclone lowers below the cloud base, it begins to take in cool, moist air from the downdraft region of the storm. This convergence of warm air in the updraft, and this cool air, causes a rotating wall cloud to form. The RFD also focuses the mesocyclone's base, causing it to siphon air from a smaller and smaller area on the ground. As the updraft intensifies, it creates an area of low pressure at the surface. This pulls the focused mesocyclone down, in the form of a visible condensation funnel. As the funnel descends, the RFD also reaches the ground, creating a gust front that can cause severe damage a good distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within a few minutes of the RFD reaching the ground.{{citation needed|date=April 2014}}
As the mesocyclone lowers below the cloud base, it begins to take in cool, moist air from the downdraft region of the storm. The convergence of this cool air and the warm air in the updraft causes a rotating wall cloud to form. The RFD also focuses the mesocyclone's base, causing it to siphon air from a smaller and smaller area on the ground. As the updraft intensifies, it creates an area of low pressure at the surface. This pulls the focused mesocyclone down, in the form of a visible condensation funnel. As the funnel descends, the RFD also reaches the ground, creating a gust front that can cause severe damage a good distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within a few minutes of the RFD reaching the ground.<ref>{{Cite web |title=Tornado Basics |url=https://www.nssl.noaa.gov/education/svrwx101/tornadoes/ |access-date=2023-10-19 |website=NOAA National Severe Storms Laboratory |language=EN-US}}</ref>


Field studies have shown that in order for a supercell to produce a tornado the RFD needs to be no more than a few Kelvin cooler than the updraft. Also the FFD ([[Forward flank downdraft#Forward Flank Downdraft (FFD)|forward flank downdraft]]) seems to be warmer within tornadic supercells than in non-tornadic supercells.{{citation needed|date=March 2018}}
Field studies have shown that in order for a supercell to produce a tornado, the RFD needs to be no more than a few kelvin cooler than the updraft. The [[Forward flank downdraft#Forward flank downdraft (FFD)|forward flank downdraft]] (FFD) also seems to be warmer within tornadic supercells than in non-tornadic supercells.<ref>{{Cite journal |last1=Shabbott |first1=Christopher J. |last2=Markowski |first2=Paul M. |date=2006-05-01 |title=Surface In Situ Observations within the Outflow of Forward-Flank Downdrafts of Supercell Thunderstorms |journal=Monthly Weather Review |language=EN |volume=134 |issue=5 |pages=1422–1441 |doi=10.1175/MWR3131.1 |issn=1520-0493|doi-access=free |bibcode=2006MWRv..134.1422S }}</ref>


Although many envision a top-down process in which a mid-level mesocyclone first forms and couples with a low-level mesocyclone or tornadocyclone and a vortex then forms below the cloud base and becomes a concentrated vortex due to convergence upon reaching the surface, it has long been observed and there is now more rapidly growing evidence that many tornadoes form first near the surface or simultaneously from the surface to low and mid levels aloft.<ref name="Houser">{{cite conference |first = Houser |last = Jana |author2 = H. Bluestein |author3 = A. Seimon |author4 = J. Snyder |author5 = K. Thiem |title = Rapid-Scan Mobile Radar Observations of Tornadogenesis |book-title = AGU Fall Meeting |pages = |publisher = American Geophysical Union |date = Dec 2018 |location = Washington, DC |url = https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/432399 |doi = }}</ref><ref>{{cite journal |last = Trapp |first = R. J. |author2 = E. D. Mitchell |title = Descending and Nondescending Tornadic Vortex Signatures Detected by WSR-88Ds |journal = Wea. Forecasting |volume = 14 |issue = 5|pages = 625–639 |date = 1999 |doi = 10.1175/1520-0434(1999)014<0625:DANTVS>2.0.CO;2 |bibcode = 1999WtFor..14..625T }}</ref>
Many envision a top-down process in which a mid-level mesocyclone first forms and couples with a low-level mesocyclone or tornadocyclone, with a vortex then forming below the cloud base and becoming a concentrated vortex due to convergence upon reaching the surface. However, observation history and more modern research indicates that many tornadoes form first near the surface or simultaneously from the surface to low and mid levels aloft.<ref name="Houser">{{cite conference |first = Houser |last = Jana |author2 = H. Bluestein |author3 = A. Seimon |author4 = J. Snyder |author5 = K. Thiem |title = Rapid-Scan Mobile Radar Observations of Tornadogenesis |book-title = AGU Fall Meeting |publisher = American Geophysical Union |date = Dec 2018 |location = Washington, DC |url = https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/432399 }}</ref><ref>{{cite journal |last = Trapp |first = R. J. |author2 = E. D. Mitchell |title = Descending and Nondescending Tornadic Vortex Signatures Detected by WSR-88Ds |journal = Wea. Forecasting |volume = 14 |issue = 5|pages = 625–639 |date = 1999 |doi = 10.1175/1520-0434(1999)014<0625:DANTVS>2.0.CO;2 |bibcode = 1999WtFor..14..625T |doi-access = free }}</ref>

See the dynamics, thermodynamics and energy source.<ref>Ben-Amots N (2016) “Dynamics and thermodynamics of tornado: Rotation effects” Atmospheric Research, v. 178-179, pp. 320-328 https://doi.org/10.1016/j.atmosres.2016.03.025</ref>{{clarify|date=October 2024}}


== Misocyclones ==
== Misocyclones ==
{{Further information|Misoscale meteorology}}
=== Waterspouts ===
=== Waterspouts ===
{{Main|Waterspout}}
{{Main|Waterspout}}
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=== Landspouts ===
=== Landspouts ===
{{Main|Landspout}}
{{Main|Landspout}}
Landspouts are tornadoes that do not form from supercells and are similar in appearance and structure to fair-weather waterspouts with the exception that they form over land instead of water. They are thought to form in a manner similar to that of weaker waterspouts<ref name="NWS-Landspout">{{cite web|url=https://www.weather.gov/grr/summary20170630|last=National Weather Service|date=June 30, 2017|accessdate=20 March 2018|title=EF-0 Landspout Tornado near Grand Junction, MI, on June 30, 2017}}</ref> in that they form during the growth stage of convective clouds by the ingestion and tightening of [[atmospheric boundary layer|boundary layer]] [[vorticity]] by the [[cumulus cloud|cumuliform]] tower's updraft.
Landspouts are tornadoes that do not form from mesocyclones. They are similar in appearance and structure to fair-weather waterspouts, except that they form over land instead of water. They are thought to form similarly to weaker waterspouts<ref name="NWS-Landspout">{{cite web|url=https://www.weather.gov/grr/summary20170630|last=National Weather Service|date=June 30, 2017|accessdate=20 March 2018|title=EF-0 Landspout Tornado near Grand Junction, MI, on June 30, 2017}}</ref> in that they form during the growth stage of convective clouds by the ingestion and tightening of [[atmospheric boundary layer|boundary layer]] [[vorticity]] by the [[cumulus cloud|cumuliform]] tower's updraft.


== Mesovortices ==
== Mesovortices ==


=== QLCS ===
=== QLCS ===
Tornadoes sometimes form with mesovortices within [[squall line]]s (QLCS, quasi-linear convective systems), most often in [[middle latitudes]] regions. Mesocyclonic tornadoes may also form with embedded supercells within squall lines.
Tornadoes sometimes form from mesovortices within [[squall line]]s (QLCS, quasi-linear convective systems), most often in [[middle latitudes]] regions. Mesocyclonic tornadoes may also form from embedded supercells within squall lines.


=== Tropical cyclones ===
=== Tropical cyclones ===
Mesovortices or mini-swirls within intense tropical cyclones, particularly within eyewalls, may lead to tornadoes. Embedded supercells may produce mesocyclonic tornadoes in the right front quadrant or particularly in certain situations with outer rainbands.
Mesovortices or mini-swirls within intense tropical cyclones, particularly within eyewalls, may lead to tornadoes. Embedded supercells may produce mesocyclonic tornadoes in the right front quadrant of the cyclone, or in certain situations within its outer rainbands.


== Fire whirls and pyro-tornadogenesis ==
== Fire whirls and pyro-tornadogenesis ==
{{Main|Fire whirl}}
{{Main|Fire whirl}}
Most fire or volcanic eruption induced whirlwinds are not tornadic vortices, however, on rare occasion circulations with large wildfires, conflagrations, or ejecta do reach an ambient cloud base, and in extremely rare cases [[pyrocumulonimbus]] with tornadic mesocyclones have been observed.
Most fire or volcanic eruption–induced whirlwinds are not tornadic vortices. However, on rare occasion, circulations with large wildfires, conflagrations, or ejecta do reach an ambient cloud base. In extremely rare cases, [[pyrocumulonimbus|pyrocumulonimbi]] with tornadic mesocyclones have been observed.{{citation needed|date=August 2024}}
<!-- == Continuing research ==
<!-- == Continuing research ==
Though these are widely accepted hypotheses for how most tornadoes form, they do not explain the formation of 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 these ones.<ref name="downdraft transport">{{cite journal |last=Markowski |first=Paul M. |authorlink=Paul M. Markowski |author2=J.M. Straka |author3=E.N. Rasmussen |title=Tornadogenesis Resulting from the Transport of Circulation by a Downdraft: Idealized Numerical Simulations |journal=J. Atmos. Sci. |volume=60 |issue=6 |pages=795–823 |date=March 2003 |url=http://ams.allenpress.com/amsonline/?request=get-document&doi=10.1175%2F1520-0469(2003)060%3C0795:TRFTTO%3E2.0.CO%3B2 |doi=10.1175/1520-0469(2003)060<0795:TRFTTO>2.0.CO;2 |bibcode=2003JAtS...60..795M }}{{Dead link|date=September 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> There are still many aspects about the formation of tornadoes which remain a mystery.<ref name="VORTEX book">"[http://www.nssl.noaa.gov/noaastory/book.html VORTEX: Unraveling the Secrets]." ''[http://www.nssl.noaa.gov/ National Severe Storms Laboratory]''.</ref> Research programs, including [[VORTEX]], deployment of [[TOtable Tornado Observatory|TOTO]] (the TOtable Tornado Observatory), and dozens of other programs, hope to solve many questions that still plague meteorologists about this topic.<ref name="tornado forecasting">{{cite web|last=Rasmussen |first=Erik |title=Tornado Forecasting |date=31 December 2000 |url=http://cimms.ou.edu/~erik/Tornadoes/Forecasting/Detailed/Detailed.htm |accessdate=2000-11-04 |url-status=dead |archiveurl=https://web.archive.org/web/20040919195117/http://cimms.ou.edu/~erik/Tornadoes/Forecasting/Detailed/Detailed.htm |archivedate=19 September 2004 }}</ref> -->
Though these are widely accepted hypotheses for how most tornadoes form, they do not explain the formation of 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 these ones.<ref name="downdraft transport">{{cite journal |last=Markowski |first=Paul M. |author-link=Paul M. Markowski |author2=J.M. Straka |author3=E.N. Rasmussen |title=Tornadogenesis Resulting from the Transport of Circulation by a Downdraft: Idealized Numerical Simulations |journal=J. Atmos. Sci. |volume=60 |issue=6 |pages=795–823 |date=March 2003 |url=http://ams.allenpress.com/amsonline/?request=get-document&doi=10.1175%2F1520-0469(2003)060%3C0795:TRFTTO%3E2.0.CO%3B2 |doi=10.1175/1520-0469(2003)060<0795:TRFTTO>2.0.CO;2 |bibcode=2003JAtS...60..795M }}{{Dead link|date=September 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> There are still many aspects about the formation of tornadoes which remain a mystery.<ref name="VORTEX book">"[http://www.nssl.noaa.gov/noaastory/book.html VORTEX: Unraveling the Secrets]." ''[http://www.nssl.noaa.gov/ National Severe Storms Laboratory]''.</ref> Research programs, including [[VORTEX]], deployment of [[TOtable Tornado Observatory|TOTO]] (the TOtable Tornado Observatory), and dozens of other programs, hope to solve many questions that still plague meteorologists about this topic.<ref name="tornado forecasting">{{cite web|last=Rasmussen |first=Erik |title=Tornado Forecasting |date=31 December 2000 |url=http://cimms.ou.edu/~erik/Tornadoes/Forecasting/Detailed/Detailed.htm |accessdate=2000-11-04 |url-status=dead |archive-url=https://web.archive.org/web/20040919195117/http://cimms.ou.edu/~erik/Tornadoes/Forecasting/Detailed/Detailed.htm |archive-date=19 September 2004 }}</ref> -->


== See also ==
== See also ==
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== Further reading ==
== Further reading ==
* {{cite journal |last = Markowski |first = Paul M. |authorlink = Paul M. Markowski |author2=Y.P. Richardson |title = Tornadogenesis: Our current understanding, forecasting considerations, and questions to guide future research |journal = Atmos. Res. |volume = 93 |issue = 1–3 |pages = 3–10 |date = Jul 2009 |url = http://bricker.met.psu.edu/~marko/pubs/2009/MR09ATMOSRES.pdf |doi = 10.1016/j.atmosres.2008.09.015 |bibcode = 2009AtmRe..93....3M }}
* {{cite journal |last = Markowski |first = Paul M. |author-link = Paul M. Markowski |author2=Y.P. Richardson |title = Tornadogenesis: Our current understanding, forecasting considerations, and questions to guide future research |journal = Atmos. Res. |volume = 93 |issue = 1–3 |pages = 3–10 |date = Jul 2009 |url = http://bricker.met.psu.edu/~marko/pubs/2009/MR09ATMOSRES.pdf |doi = 10.1016/j.atmosres.2008.09.015 |bibcode = 2009AtmRe..93....3M }}
* {{cite journal |last = Davies-Jones |first = Robert |author-link = Robert Davies-Jones |title = A review of supercell and tornado dynamics |journal = Atmos. Res. |volume = 158-159 |issue = |pages = 274–291 |date = 2015 |doi = 10.1016/j.atmosres.2014.04.007 |bibcode = 2015AtmRe.158..274D }}
* {{cite journal |last = Davies-Jones |first = Robert |author-link = Robert Davies-Jones |title = A review of supercell and tornado dynamics |journal = Atmos. Res. |volume = 158-159 |pages = 274–291 |date = 2015 |doi = 10.1016/j.atmosres.2014.04.007 |bibcode = 2015AtmRe.158..274D }}


== External links ==
== External links ==
* {{cite journal |last= Markowski |first= Paul |authorlink= Paul Markowski |author2= Y. Richardson |title= What We Know and Don't Know About Tornado Formation |journal= Phys. Today |volume= 67 |issue= 9 |pages= 26–31 |date= 2014 |doi= 10.1063/PT.3.2514 |bibcode = 2014PhT....67i..26M }}
* {{cite journal |last= Markowski |first= Paul |author-link= Paul Markowski |author2= Y. Richardson |title= What We Know and Don't Know About Tornado Formation |journal= Phys. Today |volume= 67 |issue= 9 |pages= 26–31 |date= 2014 |doi= 10.1063/PT.3.2514 |bibcode = 2014PhT....67i..26M |doi-access= free }}
* {{cite journal |last= Markowski |first= Paul |authorlink= Paul Markowski |author2= Yvette Richardson |title= How to Make a Tornado |journal= Weatherwise |volume= |issue= |pages= 12–19 |date= July–August 2013 |url= http://www.meteo.psu.edu/~pmm116/pubs/2013/howtomakeatornado.pdf |doi= }}
* {{cite journal |last= Markowski |first= Paul |author-link= Paul Markowski |author2= Yvette Richardson |title= How to Make a Tornado |journal= Weatherwise |volume= 66|issue= 4|pages= 12–19 |date= July–August 2013 |url= http://www.meteo.psu.edu/~pmm116/pubs/2013/howtomakeatornado.pdf |doi= 10.1080/00431672.2013.800413|bibcode= 2013Weawi..66d..12M |s2cid= 191649696 }}
* [https://www.crh.noaa.gov/lmk/soo/presentations/tornadogenesis.pdf Tornadogenesis in Supercells: The Three Main Ingredients] (NWS)
* [https://www.crh.noaa.gov/lmk/soo/presentations/tornadogenesis.pdf Tornadogenesis in Supercells: The Three Main Ingredients] (NWS)
* {{cite web |last = Rasmussen |first = Erik |authorlink = Erik N. Rasmussen |author2 = J. Straka |author3 = K. Kanak |title = Tornadogenesis: Unknowns. What's Left to Learn About Tornadoes? |publisher = Rasmussen Systems |year = 2009 |url = http://rasmsys.com/resources/Talks/SeCAPS2010.ppt |format = ppt |accessdate = 2012-02-14 |display-authors = etal }}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}
* {{cite web |last = Rasmussen |first = Erik |author-link = Erik N. Rasmussen |author2 = J. Straka |author3 = K. Kanak |title = Tornadogenesis: Unknowns. What's Left to Learn About Tornadoes? |publisher = Rasmussen Systems |year = 2009 |url = http://rasmsys.com/resources/Talks/SeCAPS2010.ppt |format = ppt |accessdate = 2012-02-14 |display-authors = etal }}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}
* Tornadogenesis research by [https://web.archive.org/web/20120503014522/http://www.rasmsys.com/Publications/Publications.html Erik Rasmussen et al] and [https://sites.psu.edu/pmarkowski/ Paul Markowski et al], also [http://www.cswr.org/ Josh Wurman et al]
* Tornadogenesis research by [https://web.archive.org/web/20120503014522/http://www.rasmsys.com/Publications/Publications.html Erik Rasmussen et al] and [https://sites.psu.edu/pmarkowski/ Paul Markowski et al], also [http://www.cswr.org/ Josh Wurman et al]
* Dr. Leigh Orf's [http://orf.media/ Simulation and visualization of thunderstorms, tornadoes, and downbursts]
* Dr. Leigh Orf's [http://orf.media/ Simulation and visualization of thunderstorms, tornadoes, and downbursts]


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[[Category:Tornado]]
[[Category:Tornadogenesis| ]]
[[Category:Tornadogenesis| ]]
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[[Category:Tornado]]

Latest revision as of 00:55, 8 October 2024

A sequence of images showing the birth of a supercellular tornado. First, the rain-free cloud base lowers as a rotating wall cloud. This lowering concentrates into a funnel cloud, which continues descending simultaneously as a circulation builds near the surface, kicking up dust and other debris. Finally, the visible funnel extends to the ground, and the tornado begins causing major damage.
Tornadogenesis occurring in Falcon, Colorado. Note the faint dust swirl beneath the funnel cloud.
A diagram showing the contributing weather systems to Tornado Alley in the United States, a loosely-defined area that is prone to tornadoes.

Tornadogenesis is the process by which a tornado forms. There are many types of tornadoes, varying in methods of formation. Despite ongoing scientific study and high-profile research projects such as VORTEX, tornadogenesis is a volatile process and the intricacies of many of the mechanisms of tornado formation are still poorly understood.[1][2][3]

A tornado is a violently rotating column of air in contact with the surface and a cumuliform cloud base. Tornado formation is caused by the stretching and aggregating/merging of environmental and/or storm-induced vorticity that tightens into an intense vortex. There are various ways this may come about and thus various forms and sub-forms of tornadoes. Although each tornado is unique, most kinds of tornadoes go through a life cycle of formation, maturation, and dissipation.[4] The process by which a tornado dissipates or decays, occasionally conjured as tornadolysis, is of particular interest for study as is tornadogenesis, longevity, and intensity.

Mesocyclones

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Classical tornadoes are supercellular tornadoes, which have a recognizable pattern of formation.[5] The cycle begins when a strong thunderstorm develops a rotating mesocyclone a few miles up in the atmosphere. As rainfall in the storm increases, it 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 rotating mesocyclone towards the ground with it. Storm relative helicity (SRH) has been shown to play a role in tornado development and strength. SRH is horizontal vorticity that is parallel to the inflow of the storm and is tilted upwards when it is taken up by the updraft, thus creating vertical vorticity.

As the mesocyclone lowers below the cloud base, it begins to take in cool, moist air from the downdraft region of the storm. The convergence of this cool air and the warm air in the updraft causes a rotating wall cloud to form. The RFD also focuses the mesocyclone's base, causing it to siphon air from a smaller and smaller area on the ground. As the updraft intensifies, it creates an area of low pressure at the surface. This pulls the focused mesocyclone down, in the form of a visible condensation funnel. As the funnel descends, the RFD also reaches the ground, creating a gust front that can cause severe damage a good distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within a few minutes of the RFD reaching the ground.[6]

Field studies have shown that in order for a supercell to produce a tornado, the RFD needs to be no more than a few kelvin cooler than the updraft. The forward flank downdraft (FFD) also seems to be warmer within tornadic supercells than in non-tornadic supercells.[7]

Many envision a top-down process in which a mid-level mesocyclone first forms and couples with a low-level mesocyclone or tornadocyclone, with a vortex then forming below the cloud base and becoming a concentrated vortex due to convergence upon reaching the surface. However, observation history and more modern research indicates that many tornadoes form first near the surface or simultaneously from the surface to low and mid levels aloft.[8][9]

See the dynamics, thermodynamics and energy source.[10][clarification needed]

Misocyclones

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Further information: Misoscale meteorology

Waterspouts

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Main article: Waterspout

Waterspouts are defined as tornadoes over water. However, while some waterspouts are supercellular (also known as "tornadic waterspouts"), forming in a process similar to that of their land-based counterparts, most are much weaker and caused by different processes of atmospheric dynamics. They normally develop in moisture-laden environments with little vertical wind shear in areas where wind comes together (convergence), such as land breezes, lake effect bands, lines of frictional convergence from nearby landmasses, or surface troughs. Waterspouts normally develop as their parent clouds are in the process of development. It is theorized that they spin upward as they move up the surface boundary from the horizontal shear near the surface, and then stretch upward to the cloud once the low level shear vortex aligns with a developing cumulus or thunderstorm.[11] Their parent cloud can be as innocuous as a moderate cumulus, or as significant as a supercell.

Landspouts

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Main article: Landspout

Landspouts are tornadoes that do not form from mesocyclones. They are similar in appearance and structure to fair-weather waterspouts, except that they form over land instead of water. They are thought to form similarly to weaker waterspouts[12] in that they form during the growth stage of convective clouds by the ingestion and tightening of boundary layer vorticity by the cumuliform tower's updraft.

Mesovortices

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QLCS

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Tornadoes sometimes form from mesovortices within squall lines (QLCS, quasi-linear convective systems), most often in middle latitudes regions. Mesocyclonic tornadoes may also form from embedded supercells within squall lines.

Tropical cyclones

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Mesovortices or mini-swirls within intense tropical cyclones, particularly within eyewalls, may lead to tornadoes. Embedded supercells may produce mesocyclonic tornadoes in the right front quadrant of the cyclone, or in certain situations within its outer rainbands.

Fire whirls and pyro-tornadogenesis

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Main article: Fire whirl

Most fire or volcanic eruption–induced whirlwinds are not tornadic vortices. However, on rare occasion, circulations with large wildfires, conflagrations, or ejecta do reach an ambient cloud base. In extremely rare cases, pyrocumulonimbi with tornadic mesocyclones have been observed.[citation needed]

See also

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References

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  1. ^ Coffer, Brice E.; M. D. Parker (2017). "Volatility of Tornadogenesis: An Ensemble of Simulated Nontornadic and Tornadic Supercells in VORTEX2 Environments". Mon. Wea. Rev. 145 (11): 4605–4625. Bibcode:2017MWRv..145.4605C. doi:10.1175/MWR-D-17-0152.1.
  2. ^ Trapp, R. Jeffrey; R. Davies-Jones (1997). "Tornadogenesis with and without a Dynamic Pipe Effect". J. Atmos. Sci. 54 (1): 113–133. Bibcode:1997JAtS...54..113T. doi:10.1175/1520-0469(1997)054<0113:TWAWAD>2.0.CO;2.
  3. ^ Davies-Jones, Robert (28 January 2006). "Tornadogenesis in supercell storms: What We Know and What We Don't Know". Symposium on the Challenges of Severe Convective Storms. Atlanta, GA: American Meteorological Society.
  4. ^ French, Michael M.; D. M. Kingfield (2019). "Dissipation Characteristics of Tornadic Vortex Signatures Associated with Long-Duration Tornadoes". J. Appl. Meteorol. Climatol. 58 (2): 317–339. Bibcode:2019JApMC..58..317F. doi:10.1175/JAMC-D-18-0187.1.
  5. ^ Doswell, Moller, Anderson; et al. (2005). "Advanced Spotters' Field Guide" (PDF). US Department of Commerce. Archived from the original (PDF) on 2006-08-23. Retrieved 2006-09-20. {{cite web}}: External link in |publisher= (help)CS1 maint: multiple names: authors list (link)
  6. ^ "Tornado Basics". NOAA National Severe Storms Laboratory. Retrieved 2023-10-19.
  7. ^ Shabbott, Christopher J.; Markowski, Paul M. (2006-05-01). "Surface In Situ Observations within the Outflow of Forward-Flank Downdrafts of Supercell Thunderstorms". Monthly Weather Review. 134 (5): 1422–1441. Bibcode:2006MWRv..134.1422S. doi:10.1175/MWR3131.1. ISSN 1520-0493.
  8. ^ Jana, Houser; H. Bluestein; A. Seimon; J. Snyder; K. Thiem (Dec 2018). "Rapid-Scan Mobile Radar Observations of Tornadogenesis". AGU Fall Meeting. Washington, DC: American Geophysical Union.
  9. ^ Trapp, R. J.; E. D. Mitchell (1999). "Descending and Nondescending Tornadic Vortex Signatures Detected by WSR-88Ds". Wea. Forecasting. 14 (5): 625–639. Bibcode:1999WtFor..14..625T. doi:10.1175/1520-0434(1999)014<0625:DANTVS>2.0.CO;2.
  10. ^ Ben-Amots N (2016) “Dynamics and thermodynamics of tornado: Rotation effects” Atmospheric Research, v. 178-179, pp. 320-328 https://doi.org/10.1016/j.atmosres.2016.03.025
  11. ^ Barry K. Choy and Scott M. Spratt. Using the WSR-88D to Predict East Central Florida Waterspouts. Retrieved on 2006-10-25.
  12. ^ National Weather Service (June 30, 2017). "EF-0 Landspout Tornado near Grand Junction, MI, on June 30, 2017". Retrieved 20 March 2018.

Further reading

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