A rainband is a

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...

and

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 ...

structure associated with an area of rainfall which is significantly elongated. Rainbands in

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 ...

s can be either stratiform or

convective Convection is single or multiphase fluid flow that occurs spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

and are curved in shape. They consist of showers and thunderstorms, and along with the eyewall and the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

, they make up a tropical cyclone. The extent of rainbands around a tropical cyclone can help determine the cyclone's intensity. Rainbands spawned near and ahead of

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 (meteorology), trough of Low-pressure area, low pressure. It often forms behind an extratropica ...

s can be

squall line A squall line, or quasi-linear convective system (QLCS), is a line of thunderstorms, often forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front (which often are accompanied by abrupt a ...

s which are able to produce

tornado 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 ...

es. Rainbands associated with cold fronts can be warped by mountain barriers perpendicular to the front's orientation due to the formation of a low-level barrier jet. Bands of thunderstorms can form with

sea breeze A sea breeze or onshore breeze is a wind that blows in the afternoon from a large body of water toward or onto a landmass. By contrast, a land breeze or offshore breeze is a wind that blows in the night from a landmass toward or onto a large ...

and

land breeze A sea breeze or onshore breeze is a wind that blows in the afternoon from a large body of water toward or onto a landmass. By contrast, a land breeze or offshore breeze is a wind that blows in the night from a landmass toward or onto a large ...

boundaries, if enough moisture is present. If sea breeze rainbands become active enough just ahead of a cold front, they can mask the location of the cold front itself. Banding within the comma head precipitation pattern of an

extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of p ...

can yield significant amounts of

rain Rain is a form of precipitation where water drop (liquid), droplets that have condensation, condensed from Water vapor#In Earth's atmosphere, atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is res ...

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

. Behind extratropical cyclones, rainbands can form downwind of relative warm bodies of water such as the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

. If the atmosphere is cold enough, these rainbands can yield heavy

Extratropical cyclones

Rainbands in advance of warm

occluded front In meteorology, an occluded front is a type of weather front formed during cyclogenesis. The classical and usual view of an occluded front is that it starts when a cold front overtakes a warm front near a cyclone, such that the warm air is sepa ...

s and

warm front Warm, WARM, or Warmth may refer to: * A somewhat high temperature; heat * Kindness Music Albums * ''Warm'' (Herb Alpert album), 1969 * ''Warm'' (Jeff Tweedy album), 2018 * ''Warm'' (Johnny Mathis album), 1958, and the title song * ''Warm'' ( ...

s are associated with weak upward motion, and tend to be wide and stratiform in nature. In an atmosphere with rich low level moisture and vertical

wind shear Wind shear (; also written 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 ...

, narrow, convective rainbands known as

s form generally in the

cyclone In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an ant ...

's warm sector, ahead of strong cold fronts associated with extratropical cyclones. Wider rain bands can occur behind cold fronts, which tend to have more stratiform, and less convective, precipitation. Within the cold sector north to northwest of a cyclone center, in colder cyclones, small scale, or mesoscale, bands of heavy snow can occur within a cyclone's comma head precipitation pattern with a width of to . These bands in the comma head are associated with areas of frontogensis, or zones of strengthening temperature contrast. Southwest of

s, curved flow bringing cold air across the relatively warm

can lead to narrow

lake-effect snow Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer lake water. The lower layer of air, heated by the lake water, picks up water vapor from the lake and rises through colde ...

bands which bring significant localized snowfall.

Narrow cold-frontal rainband

A narrow cold-frontal rainband (NCFR) is a characteristic of particularly sharp cold frontal boundaries. These can usually be seen very easily on satellite photos. NCFRs are typically accompanied by strong gusty winds and brief but intense rainfall. Convection may or may not occur depending on the stability of the air mass being lifted by the front. Such fronts usually are also marked by a sharp wind shift and temperature drop.

Tropical cyclones

Rainbands exist in the periphery of tropical cyclones, which point towards the cyclone's center of low pressure. Rainbands within tropical cyclones require ample moisture and a low level pool of cooler air. Bands located to from a cyclone's center migrate outward. They are capable of producing heavy rains and

squall A squall is a sudden, sharp increase in wind speed lasting minutes, as opposed to a wind gust, which lasts for only seconds. They are usually associated with active weather, such as rain showers, thunderstorms, or heavy snow. Squalls refer to the ...

s of wind, as well as

es, particularly in the storm's right-front quadrant. Some rainbands move closer to the center, forming a secondary, or outer, eyewall within intense hurricanes. Spiral rainbands are such a basic structure to a tropical cyclone that in most tropical cyclone basins, use of the satellite-based

Dvorak technique The Dvorak technique (developed between 1969 and 1984 by Vernon Dvorak) is a widely used system to estimate tropical cyclone intensity (which includes tropical depression, tropical storm, and hurricane/typhoon/intense tropical cyclone intensities ...

is the primary method used to determine a tropical cyclone's maximum sustained winds.

University of Wisconsin–Madison The University of Wisconsin–Madison (University of Wisconsin, Wisconsin, UW, UW–Madison, or simply Madison) is a public land-grant research university in Madison, Wisconsin, United States. It was founded in 1848 when Wisconsin achieved st ...

(1998
Objective Dvorak Technique.
Retrieved on 2006-05-29. Within this method, the extent of spiral banding and difference in temperature between the

and eyewall is used to assign a maximum sustained wind and a central pressure. Central pressure values for their centers of low pressure derived from this technique are approximate. Different programs have been studying these rainbands, including the Hurricane Rainband and Intensity Change Experiment.

Forced by geography

Convective rainbands can form parallel to terrain on its

windward In geography and seamanship, windward () and leeward () are directions relative to the wind. Windward is ''upwind'' from the point of reference, i.e., towards the direction from which the wind is coming; leeward is ''downwind'' from the point ...

side, due to lee waves triggered by hills just upstream of the cloud's formation. Their spacing is normally to apart. When bands of precipitation near frontal zones approach steep topography, a low-level barrier

jet stream Jet streams are fast flowing, narrow thermal wind, air currents in the Earth's Atmosphere of Earth, atmosphere. The main jet streams are located near the altitude of the tropopause and are westerly winds, flowing west to east around the gl ...

forms parallel to and just prior to the mountain ridge, which slows down the frontal rainband just prior to the mountain barrier. If enough moisture is present,

and

fronts can form convective rainbands. Sea breeze front

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 ...

lines can become strong enough to mask the location of an approaching cold front by evening. The edge of

ocean currents An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours ...

can lead to the development of thunderstorm bands due to heat differential at this interface. Downwind of islands, bands of showers and thunderstorms can develop due to low level wind convergence downwind of the island edges. Offshore

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, this has been noted in the wake of cold fronts.Ivory J. Small (1999)
AN OBSERVATIONAL STUDY OF ISLAND EFFECT BANDS: PRECIPITATION PRODUCERS IN SOUTHERN CALIFORNIA.
Retrieved on 2008-12-26.

References

External links

* * * {{Cyclones Precipitation Extratropical cyclones Storm Weather hazards Tropical cyclone meteorology Mesoscale meteorology