{{Short description|Small-scale rotational weather feature}} A '''mesovortex''' is a small-scale rotational feature found in a convective storm, such as a quasi-linear convective system (QLCS), a supercell, or the eyewall of a tropical cyclone.<ref>{{Cite journal |last=Weisman |first=M. L. |author2=Trapp, R. J. |date=November 2003 |title=Low-Level Mesovortices within Squall Lines and Bow Echoes. Part I: Overview and Dependence on Environmental Shear |journal=Monthly Weather Review |volume=131 |issue=11 |pages=2779–2803 |doi=10.1175/1520-0493(2003)131<2779:LMWSLA>2.0.CO;2 |doi-access=free |bibcode=2003MWRv..131.2779W }}</ref><ref name="Vortical Swirls">{{Cite journal |last1=Kossin |first1=J. P. |last2=McNoldy|first2=B. D. |last3=Schubert | first3= W. H. |date=December 2002 |title=Vortical Swirls in Hurricane Eye Clouds |journal=Monthly Weather Review |volume=130 |issue=12 |pages=3144–3149 |doi=10.1175/1520-0493(2002)130<3144:VSIHEC>2.0.CO;2|doi-access=free|bibcode=2002MWRv..130.3144K }}</ref> Mesovortices range in diameter from tens of miles to a mile or less<ref>{{cite web|url=https://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm#types|title=Facts About Derechos|publisher=National Oceanic and Atmospheric Administration|access-date=June 12, 2013}}</ref> and can be immensely intense.
==Eyewall mesovortex== [[File:Hurricane emilia (1994) eye close-up.jpg|thumb|upright=0.75|Mesovortices visible in the eye of Hurricane Emilia in 1994.]]
An ''eyewall mesovortex'' is a small-scale rotational feature found in an eyewall of an intense tropical cyclone. Eyewall mesovortices are similar, in principle, to small "suction vortices" often observed in multiple-vortex tornadoes. In these vortices, wind speed can be up to 10% higher than in the rest of the eyewall. Eyewall mesovortices are most common during periods of intensification in tropical cyclones.
Eyewall mesovortices often exhibit unusual behavior in tropical cyclones. They usually revolve around the low pressure center, but sometimes they remain stationary. Eyewall mesovortices have even been documented to cross the eye of a storm. These phenomena have been documented observationally,<ref name="Vortical Swirls"/> experimentally,<ref name="Experimental Study">{{cite journal | author=Montgomery, M. T., V. A. Vladimirov, and P. V. Denissenko | title=An experimental study on hurricane mesovortices | journal=Journal of Fluid Mechanics | year= 2002 | volume=471 | issue=1 | pages=1–32 | publisher=Journal of Fluid Mechanics: Vol. 471, pp. 1–32 | doi=10.1017/S0022112002001647 | bibcode=2002JFM...471....1M | s2cid=6744823 | url = https://journals.cambridge.org/action/displayFulltext?type=1&fid=128928&jid=FLM&volumeId=471&issueId=-1&aid=128927| url-access=subscription }}</ref> and theoretically.<ref name="Mesovortices"> {{cite journal |last1=Kossin |first1=J. P. |last2=Schubert |first2=W. H. |date=August 2001 |title=Mesovortices, Polygonal Flow Patterns, and Rapid Pressure Falls in Hurricane-Like Vortices |url=https://journals.ametsoc.org/view/journals/atsc/58/15/1520-0469_2001_058_2196_mpfpar_2.0.co_2.xml |journal=Journal of the Atmospheric Sciences |volume=58 |issue=15 |pages=2196–2209 |doi=10.1175/1520-0469(2001)058<2196:MPFPAR>2.0.CO;2 |bibcode=2001JAtS...58.2196K |access-date=July 1, 2024}}</ref>
Eyewall mesovortices are a significant factor in the formation of tornadoes after tropical cyclone landfall. Mesovortices can spawn rotation in individual thunderstorms (a mesocyclone), which leads to tornadic activity. At landfall, friction is generated between the circulation of the tropical cyclone and land. This can allow the mesovortices to descend to the surface, causing large outbreaks of tornadoes.
<!--thumb|Illustration of mesovotices that resulted in damage to a hurricane hunter aircraft. Image from Aircrash Investigation Season 13, Episode 6--> On 15 September 1989, during observations for Hurricane Hugo, Hunter NOAA42 accidentally flew through an eyewall mesovortex measuring {{convert|320|km/h|mph|abbr=on}} and experienced crippling G-forces of +5.8Gs and -3.7Gs. The winds ripped off the propeller de-icing boot and pushed the flight down to a perilous {{convert|1000|ft|abbr=on}} above sea level. The ruggedized Lockheed WP-3D Orion was only designed for a maximum of +3.5Gs and −1G.{{citation needed|date=October 2022}}
==Mesocyclone== {{Main|Mesocyclone}} [[Image:Greensburg3 small.gif|thumb|A mesocyclone from the Greensburg, Kansas tornado indicated on Doppler weather radar.]]
A ''mesocyclone'' is a type of mesovortex, approximately {{convert|1|to|10|km|sigfig=1|abbr=on}} in diameter (the mesoscale of meteorology), within a convective storm.<ref name="MesocyloneDef">{{cite web| title = American Meteorological Society Glossary - Mesocyclone| publisher = Allen Press| year = 2000| url = http://amsglossary.allenpress.com/glossary/search?id=mesocyclone1| access-date = 2006-12-07| archive-url = https://web.archive.org/web/20060709233434/http://amsglossary.allenpress.com/glossary/search?id=mesocyclone1| archive-date = 2006-07-09}}</ref> Mesocyclones are air that rises and rotates around a vertical axis, usually in the same direction as low pressure systems in a given hemisphere. They are most often associated with a localized low-pressure region within a severe thunderstorm. Mesocyclones are believed to form when strong changes of wind speed and/or direction with height ("wind shear") sets parts of the lower part of the atmosphere spinning in invisible tube-like rolls. The convective updraft of a thunderstorm is then thought to draw up this spinning air, tilting the air's axis of rotation upward (from parallel to the ground to perpendicular) and causing the entire updraft to rotate as a vertical column. Mesocyclones are normally relatively localized: they lie between the synoptic scale (hundreds of kilometers) and small scale (hundreds of meters). Radar imagery is used to identify these features. {{clear}}
== Mesoscale convective vortex == thumb|Radar loop from KDVN on the afternoon of June 16, 2024, depicting a strong mesoscale convective vortex with a clear eye.
A ''mesoscale convective vortex'' (MCV) is a low-pressure center (mesolow) within a mesoscale convective system (MCS) that pulls winds into a circling pattern, or vortex. With a core only {{convert|30|to|60|mi|km|abbr=on}} wide and {{convert|1|to|3|mi|km|abbr=on}} deep, an MCV is often overlooked in standard surface observations.<ref name=NSSL>{{cite web| url= http://www.nssl.noaa.gov/education/svrwx101/thunderstorms/types/| title= Thunderstorm Types | work = Severe Weather 101 | author= WFO Paducah, KY | publisher= National Weather Service | access-date= May 2, 2016}}</ref> They have most often been detected on radar and satellite, particularly with the higher resolution and sensitivity of WSR-88D, but with the advent of mesonets, these mesoscale features can also be detected in surface analysis.
An MCV can persist for more than 12 hours after its parent MCS has dissipated. This orphaned MCV will sometimes then become the seed of the next thunderstorm outbreak. Their remnants will often lead to an "agitated area" of increased cumulus activity that can eventually become an area of thunderstorm formation. Associated low-level boundaries left behind can themselves cause convergence and vorticity that can increase the level of organization and intensity of any storms that do form.
An MCV that moves into tropical waters, such as the Gulf of Mexico, can serve as the nucleus for a tropical cyclone (as in the case of Hurricane Barry in 2019, for instance). MCVs, like mesovortices, often cause an intensification of convective downburst winds and can lead to tornadogenesis.<ref name=NSSL/> One form of MCV is the "comma head" of a line echo wave pattern (LEWP).
=== Example of May 2009 Mid-Mississippi Valley MCV === {{main|May 2009 Southern Midwest derecho}} On Friday, May 8, 2009, a major MCV controversially dubbed an "inland hurricane" by local media moved through southern Missouri, southern Illinois, western Kentucky, and southwestern Indiana, killing at least six and injuring dozens more. Damage estimates were in the hundreds of millions. Top speeds of {{convert|106|mi/h|km/h|abbr=on}} were reported in Carbondale, Illinois.<ref>{{cite web| url=http://www.crh.noaa.gov/news/display_cmsstory.php?storyid=27320 | title= Updated: What was it that caused the May 8 windstorm? | author= NSSL | publisher= National Weather Service | access-date= May 2, 2016}}</ref><ref>{{cite web| url=http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2009/05/090508_g12_ir_anim.gif| title= Radar loop| author= CIMSS | publisher= University of Wisconsin | access-date= May 2, 2016}}</ref><ref>{{cite web| url=http://blogs.chron.com/sciguy/archives/2009/05/midwest_experie.html| title= Midwest experiences an inland hurricane| author= Eric Berger | author-link=Eric Berger (meteorologist) | publisher= Chron | date= May 10, 2009| access-date= May 2, 2016}}</ref><ref>{{cite news| url=https://www.nytimes.com/2009/05/10/us/10storm.html | work=The New York Times | title=Storms Cut Through Midwest, Killing 5 | date=May 10, 2009}}</ref>
== See also == * Convective storm detection * Wake low * Derecho * Mesoscale convective complex (MCC) * Rear-inflow jet (RIJ) * Bow echo
==References== {{reflist|2}} {{Cyclones}}
==External links== * [http://www.crh.noaa.gov/lsx/?n=My2404QLCS A National Weather Service case study on linear mesovortices] * [http://weather.gov/glossary/ NOAA Glossary] * {{cite journal |last1=Houze |first1=R.A. Jr. |year=2004 |title=Mesoscale convective systems |journal=Rev. Geophys. |volume=42 |issue=4 |page=RG4003 |doi=10.1029/2004RG000150 |bibcode = 2004RvGeo..42.4003H |s2cid=53409251 |doi-access=free }}
Category:Mesoscale meteorology Category:Radar meteorology Category:Severe weather and convection Category:Types of cyclone Category:Tornadogenesis