The rear-inflow jet is a component of

bow echo A bow echo is the characteristic radar return from a mesoscale convective system that is shaped like an archer's bow. These systems can produce severe straight-line winds and occasionally tornadoes, causing major damage. They can also become ...

es in a

mesoscale convective system A mesoscale convective system (MCS) is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than extratropical cyclones, and normally persists for several hours or more. A mesoscale conv ...

that aids in creating a stronger cold pool and

downdraft In meteorology, an updraft (British English: ''up-draught'') is a small-scale current of rising air, often within a cloud. Overview Vertical drafts, known as updrafts or downdrafts, are localized regions of warm or cool air that move vertically ...

. The jet forms as a response to a convective circulation having upshear tilt and horizontal

pressure gradient In hydrodynamics and hydrostatics, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular locat ...

s. The cold pool that comes from the outflow of a storm forms an area of

high pressure In science and engineering the study of high pressure examines its effects on materials and the design and construction of devices, such as a diamond anvil cell, which can create high pressure. ''High pressure'' usually means pressures of thousan ...

at the surface. In response to the surface high and warmer temperatures aloft due to

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

, a mid-level mesolow forms behind the leading edge of the storm. With a mid-level area of

low pressure In meteorology, a low-pressure area (LPA), low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. It is the opposite of a high-pressure area. Low-pressure areas are commonly associated with inclem ...

, air is drawn in under the trailing stratiform region of

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

. As air is drawn in on the rear side of the storm, it begins to descend as it approaches the front line of the cells. Before reaching the leading edge, the jet descends to the surface as a strong downdraft, creating

straight-line winds In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. It originate ...

. Any mature mesoscale convective system is capable of developing its own rear-inflow jet, but questions remain as to what influences the strength of the jet. While the diabatic effects of sublimation,

melting Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which inc ...

and

evaporation Evaporation is a type of vaporization that occurs on the Interface (chemistry), surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evapora ...

play a role in influencing jet strength, these effects do not account for cases with strong rear-inflow jets. However, the diabatic effects are responsible for the jet subsiding behind the leading edge of the MCS. The sinking of the jet first starts when the mid level inflow goes under the trailing stratiform cloud before descending to the melting layer. There are other factors that contribute to the strength of any rear inflow jet. The strength of a rear inflow jet can be greatly increased with induced

vortices In fluid dynamics, a vortex (: vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...

at the end of the line, called "line-end vortices" or "book-end vortices." These vortices at either end of the line will help reinforce the rear inflow towards the center of the line. The other factor that can help strengthen the jet is an environment in which the large scale flow is feeding/forcing mid-level air into the rear end of the storm.

References

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See also

References

Further reading