An anticyclonic storm is a

storm A storm is any disturbed state of the natural environment or the atmosphere of an astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstorm), ...

with a high-pressure center, in which winds flow in the direction opposite to that of the flow above a region of low pressure. These storms can create powerful mesoanticylonic

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 ( ...

storms that can generate anticyclonic

tornado A tornado is a violently rotating column of air that is in contact with both the surface of the 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, altho ...

es. Examples include the anticyclonic blizzard of 2018, Hartmut, and Neptune's anticyclonic cloud system.

Description

Anticyclonic An anticyclone is a weather phenomenon defined as a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere as viewed from abov ...

storms usually form around high-pressure systems where air moves apart and sinks. Air at the center of these storms is forced away from the high pressure zones and replaced by a downdraft of air from higher altitudes. Anticyclonic storms have fewer clouds than cyclonic storms, due to a lower humidity. This lower humidity is caused by the air compressing and heating up as it moves downward. Anticyclonic storms, as high-pressure systems, usually accompany cold weather and are frequently a factor in large

snowstorm A winter storm is an event in which wind coincides with varieties of precipitation that only occur at freezing temperatures, such as snow, mixed snow and rain, or freezing rain. In temperate continental climates, these storms are not necessar ...

s. Along a

cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. It often forms behind an extratropical cyclone (to the west in the Northern ...

, an anticyclonic storm is called a

wave In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (re ...

, frontal, or

mid-latitude The middle latitudes (also called the mid-latitudes, sometimes midlatitudes, or moderate latitudes) are a spatial region on Earth located between the Tropic of Cancer (latitudes 23°26'22") to the Arctic Circle (66°33'39"), and Tropic of Capric ...

anticyclonic storm when they are connected to a

weather front A weather front is a boundary separating air masses for which several characteristics differ, such as air density, wind, temperature, and humidity. Disturbed and unstable weather due to these differences often arises along the boundary. For in ...

. Due to the

Coriolis effect In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the ...

, anticyclonic storms involve clockwise flow in the Northern Hemisphere and counterclockwise flow in the Southern Hemisphere.

Antimesocyclonic supercells

Supercells are long-lasting convective storms that are formed when

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

are accompanied by strong vertical

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizont ...

. For an antimesocyclone to form, there must be strong convective energy for cloud systems to be heavily reinforced with moist air. A supercell has a rotating

updraft In meteorology, an updraft is a small-scale current of rising air, often within a cloud. Overview Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding regi ...

(mid-altitude mesocyclone) and a

downdraft In meteorology, an updraft is a small-scale current of rising air, often within a cloud. Overview Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, ...

. The rotating updraft typically moves to the right. When it moves to the left (anticyclonically), mesoanticylonic super-cells are created. Anticyclonic supercells can produce hail storms, but rarely produce anticyclonic tornados.

Anticyclonic tornadoes

Tornadoes'

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 ...

are low-pressure regions, but tornadoes rotate anticyclonically because tornadoes occur on a small enough scale that Coriolis effect is negligible. Anticyclonic supercells can go through

tornadogenesis 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, tornadogenesis is a volatile pro ...

to develop into

anticyclonic tornado An anticyclonic tornado is a tornado which rotates in a clockwise direction in the Northern Hemisphere and a counterclockwise direction in the Southern Hemisphere. The term is a naming convention denoting the anomaly from normal rotation which is ...

es.

Examples

* Hartmut, Scandinavia: From 25 February – 4 March 2018, a

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive region, geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a ...

n airmass triggered a rare instance of an "anticyclonic blizzard" during an exceptionally strong anticyclone with hurricane-force maximum gusts of 187 km/h (116 mph) and peak central pressure of 1056

hPa HPA may refer to: Organizations * Harry Potter Alliance, a charity * Halifax Port Authority, Canada * Hamburg Port Authority, Germany * Hawaii Preparatory Academy, a school in Hawaii, US * Health Protection Agency, UK * Heerespersonalamt, the Ger ...

. It caused the ''Beast from the East'', a deadly

cold wave A cold wave (known in some regions as a cold snap, cold spell or Arctic Snap) is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in tem ...

that channeled freezing air and large amounts of snow over Europe. The interaction of Anticyclone Hartmut and Cyclone Emma intensified the wind and snowfall threat in Western Europe, particularly the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

. * Neptune: In 1989,

Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, '' Voyager 1'', o ...

discovered an anticyclonic cloud system (DS2) in

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

at 55°S on Neptune. There were bright and high clouds associated with this system with an anticyclonic

vortex 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 ...

. These cloud systems on Neptune are known as 'companion clouds' because they are formed similarly to the cloud structures on Earth that can lead to anticyclonic storms. Voyager 2 discovered

where one of which resembled anticyclonic behavior. This convective storm was located in the DS2 anticyclone located at 55°S. There were bright and high clouds associated with this system with an anticyclonic

References

External links