A severe thunderstorm outbreak, also called a severe weather outbreak or simply a severe outbreak, is an event in which a weather system or combination of weather systems produces a multitude of

severe thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...

s in a region over a continuous span of time. A severe outbreak which is most notable for its

tornadoes A tornado is a violently rotating column of air that is in contact with the surface of Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the ...

is called a

tornado outbreak A tornado outbreak is the occurrence of multiple tornadoes spawned by the same Synoptic scale meteorology, synoptic scale weather system. The number of tornadoes required to qualify as an outbreak typically are at least six to ten, with at least ...

. The four kinds of severe weather produced in these outbreaks are

, severe wind, large hail, and

flash flooding A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash flo ...

Types

Tornado outbreak

A tornado outbreak is the occurrence of multiple tornadoes in a region over a relatively short span of time. Usually, a tornado outbreak is the result of multiple

supercell A supercell is a thunderstorm characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms (su ...

Derecho or other squall line

A squall line (commonly abbreviated SQLN) is a line of thunderstorms, most or all of which have attained

severe Severity or Severely may refer to: * ''Severity'' (video game), a canceled video game * "Severely" (song), by South Korean band F.T. Island See also

* * {{disambig ...

limits, traveling in an organized fashion. The greatest threats within a SQLN are damaging

winds Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

, large

hail Hail is a form of solid Precipitation (meteorology), precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailsto ...

, and

, though tornadoes are possible. A derecho is a squall line which is long-lived and consistently produces damaging winds across its entire track. Derechos almost exclusively cause flash flooding and wind damage, which can be very severe.

Mesoscale convective system

A mesoscale convective system is a mesoscale organized system which may produce severe weather along a relatively narrow area or path. The greatest threats in an mesoscale convective system are damaging

, large

, and

, though

are occasionally possible.

Mesoscale convective vortex

A mesoscale convective vortex is a

tropical cyclone A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...

-like, warm core, a feature which may develop in a squall line, derecho, or MCS. Severe MCVs can become what are essentially small tropical storms or hurricanes, and can in fact become such cyclones, as in the case of

Hurricane Barry The name Barry has been used for eight tropical cyclones worldwide: seven in the Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approxim ...

in July 2019.{{Cite web , last=Shepherd , first=Marshall , title=A Look Back At The Forecast For Hurricane Barry - Success Or Bust? , url=https://www.forbes.com/sites/marshallshepherd/2019/07/15/a-look-back-at-the-forecast-for-hurricane-barry-success-or-bust/ , access-date=2024-04-12 , website=Forbes , language=en An MCV will often trail a squall line on its south side. The greatest threats in an MCV are (in the center of circulation and south of the center) extreme

and (north of the center)

, in addition to

formation.

References

Weather hazards