Amesovortex is a small-scalerotational feature found in aconvective storm, such as a quasi-linear convective system (QLCS, i.e.squall line), asupercell, or theeyewall of atropical cyclone.[1][2] Mesovortices range in diameter from tens of miles to a mile or less[3] and can be immensely intense.
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Aneyewall 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 inmultiple-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,[2] experimentally,[4] and theoretically.[5]
Eyewall mesovortices are a significant factor in the formation oftornadoes after tropical cyclone landfall. Mesovortices can spawn rotation in individual thunderstorms (amesocyclone), 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.
On 15 September 1989, during observations forHurricane Hugo, Hunter NOAA42 accidentally flew through an eyewall mesovortex measuring 320 km/h (200 mph) and experienced cripplingG-forces of +5.8Gs and -3.7Gs. The winds ripped off the propeller de-icing boot and pushed the flight down to a perilous 1,000 ft (300 m) above sea level. The ruggedizedLockheed WP-3D Orion was only designed for a maximum of +3.5Gs and −1G.[citation needed]
Amesocyclone is a type of mesovortex, approximately 1 to 10 km (0.6 to 6 mi) in diameter (themesoscale of meteorology), within aconvectivestorm.[6] 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 asevere 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 thesynoptic scale (hundreds of kilometers) and small scale (hundreds of meters). Radar imagery is used to identify these features.
Amesoscale convective vortex (MCV) is alow-pressure center (mesolow) within amesoscale convective system (MCS) that pulls winds into a circling pattern, or vortex. With a core only 30 to 60 mi (48 to 97 km) wide and 1 to 3 mi (1.6 to 4.8 km) deep, an MCV is often overlooked in standardsurface observations.[7] They have most often been detected onradar andsatellite, particularly with the higher resolution and sensitivity ofWSR-88D, but with the advent ofmesonets, thesemesoscale features can also be detected insurface 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 ofthunderstorm formation. Associated low-levelboundaries left behind can themselves causeconvergence andvorticity that can increase the level of organization and intensity of any storms that do form.
An MCV that moves into tropical waters, such as theGulf of Mexico, can serve as the nucleus for a tropical cyclone (as in the case ofHurricane Barry in 2019, for instance). MCVs, like mesovortices, often cause an intensification of convectivedownburst winds and can lead totornadogenesis.[7] One form of MCV is the "comma head" of aline echo wave pattern (LEWP).
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 106 mph (171 km/h) were reported inCarbondale, Illinois.[8][9][10][11]
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