Mackerel breeze-
(Also called mackerel gale.) A wind that ruffles the water, favoring the catching of mackerel.
Maestro-
A northwesterly wind with fine weather that blows, especially in summer, in the Adriatic; it is most frequent on the western shore and is equivalent to the etesians of the eastern Mediterranean. It is also found on the coasts of Corsica and Sardinia. Compare mistral.
Maloja wind-
A wind, named after the Maloja Pass between the Engadine and Bergall, Switzerland, that blows down the valley of the Upper Engadine by day and either up or down by night. This deviation from the usual nature of mountain and valley winds is attributed to the fact that the stronger daytime valley wind from the south overtops the ridge and continues down the Engadine.
Mamatele-
(Also called mamaliti, mamatili.) A light northwest wind of Sicily; a form of mistral.
Mamma cloud-
(Also called mammatus.) Hanging protuberances, like pouches, on the undersurface of a cloud. This supplementary cloud feature occurs mostly with cirrus, cirrocumulus, altocumulus, altostratus, stratocumulus, and cumulonimbus; in the case of cumulonimbus, mamma generally appear on the underside of the anvil (incus). See cloud classification.
Marin-
A warm moist southeast wind from the sea on the French Mediterranean coast and in the Maritime Alps, especially frequent in spring and autumn. In the Rhône delta it blows also from the south. The marin is associated with depressions that cross southern France or northern Spain and the Gulf of Lions. Generally, it is strong and regular, sometimes violent and turbulent in hilly country as the ayalas in the Massif Central; it is very humid, cloudy with hill fog, and often rainy (unless unaccompanied by fronts, when it is the marin blanc). The heavy rains, which may continue for one or two days on the mountain slopes, cause dangerous river floods. On the western slope of the Cévennes it becomes the autan. In the southern Cévennes the marin is called the aygalas. On the coast of Catalonia (northeast Spain) and Roussillon (southern France) it is the marinada and generally occurs with a depression centered over or south of the Gulf of Gascony. Compare sirocco.
Marine climate-
(Also called maritime climate, oceanic climate.) A regional climate under the predominant influence of the sea, characterized by relatively small seasonal variations and high atmospheric moisture content; the antithesis of a continental climate.
Maritime cloud-
A cloud forming in maritime air containing relatively low concentrations of cloud condensation nuclei. These clouds are characterized by a broader droplet size distribution and low droplet concentrations (some 1/100 cm3). See continental cloud.
Matanuska wind-
The local name, taken from the Matanuska River, for a strong, gusty, northeast wind that occasionally occurs during the winter in the vicinity of Palmer, Alaska.
Matinal-
The morning wind, that is, an east wind. In the Morvan Mountains and the center of the Massif Central in France, the matinal often blows for several days, especially in summer, and brings fine weather. On winter mornings a northeast or east wind descends the western slopes of the Alps (where it is known as the matinière) bringing cold and generally fine weather. Compare solaire.
Mechanical internal boundary layer-
(Abbreviated MIBL.) An internal boundary layer caused by advection of air across a discontinuity in surface roughness. When the new surface is rougher than the old one, the MIBL depth grows roughly as the 0.8 power of the ratio of the two roughness lengths. In this example, the MIBL grows to include the whole surface layer.
Mechanical turbulence-
Turbulence produced by shear flow.
Mediterranean front-
A front that forms in the low pressure zone that covers the Mediterranean between the cold air over Europe and the warm air over the Sahara.
Mei yu front-
(Also called baiu front). A quasi persistent, nearly stationary, east west oriented weak baroclinic zone in the lower troposphere that typically stretches from the east China coast, across Taiwan, and eastward into the Pacific, south of Japan. The term mei yu is the Chinese expression for plum rains. The mei yu front generally occurs from mid to late spring through early to midsummer. This low level baroclinic zone typically lies beneath a confluent jet entrance region aloft situated downstream of the Tibetan Plateau. The mei yu/baiu front is very significant in the weather and climate of southeast Asia as it serves as the focus for persistent heavy convective rainfall associated with mesoscale convective complexes (MCCs) or mesoscale convective systems (MCSs) that propagate eastward along the baroclinic zone. The moisture source is typically the South China Sea and sometimes the Bay of Bengal. The usual lifting mechanism is low level warm air advection in association with a low level jet on the equatorward flank of the baroclinic zone. Deep ascent and resulting organized MCCs/MCSs are especially favored when the low level warm air advection is situated beneath the favorable equatorward jet entrance region aloft.
Meltem-
1. (Also spelled meltEmi.) A strong wind from the northeast or east that often sets in suddenly and blows during the day in summer on the Bulgarian coast and in the Bosporus. 2. Same as monsoon.
Melting layer-
The altitude interval throughout which ice phase precipitation melts as it descends. The top of the melting layer is the melting level. The melting layer may be several hundred meters deep, reflecting the time it takes for all the hydrometeors to undergo the transition from solid to liquid phase. The temperature of the melting layer is typically 0 degree C or slightly warmer. See bright band.
Melting level-
The altitude at which ice crystals and snowflakes begin to melt as they descend through the atmosphere. In cloud physics and in radar meteorology, this is the accepted term for the 0 degree C constant temperature surface (see bright band). It is physically more apt than the corresponding operational term, freezing level, for melting of pure ice must begin very near 0 degree C, but freezing of liquid water can occur over a broad range of temperatures (between 0 degree and minus 40 degree C; see supercooling). See also freezing point, ice point, melting point.
Mergozzo-
Northwest wind on Lake Maggiore, Italy.
Meridional wind-
The wind or wind component along the local meridian, as distinguished from the zonal wind. In a horizontal coordinate system fixed locally with the x axis directed eastward and the y axis northward, the meridional wind is positive if from the south, and negative if from the north.
Mesoanalysis-
The representation of temperature, moisture, pressure, and wind variations on horizontal scales of 10 to 100 km. The analysis seeks to define mesoscale features of the observed temperature, pressure, moisture, and wind fields that can be related to important local and regional circulations that in turn may have a significant impact on local and regional weather systems. The mesoanalysis differs from the more conventional synoptic scale representation of the wind and pressure features in that smaller scale features inherent in the wind, pressure, and moisture fields are retained in the analysis.
Mesoanticyclone-
An anticyclonically rotating vortex, around 2to10 km in diameter, in a convective storm.
Mesochart-
A means to illustrate a mesoanalysis. Important mesoscale features in the wind, temperature, moisture, and pressure fields are illustrated on the mesochart by means of contours and/or colored (or black and white) shading.
Mesoclimate-
The climate of a natural region of small extent, for example, valley, forest, plantation, and park. Because of subtle differences in elevation and exposure, the climate may not be representative of the general climate of the region.
Mesoclimatology-
The study of mesoclimates; the climatology of relatively small areas that may not be climatically representative of the general region. The data used in mesoclimatology are mostly standard observations. The size of the area involved is rather indefinite and may include topographic or landscape features from a few acres to a few square miles, such as a small valley, a forest clearing, a beach, or a village site.
Mesocyclone-
A cyclonically rotating vortex, around 2to10 km in diameter, in a convective storm. The vorticity associated with a mesocyclone is often on the order of (1/10)2 1/s or greater. (It should be noted that a mesocyclone is not just any cyclone on the mesoscale; it refers specifically to cyclones within convective storms.) Mesocyclones are frequently found in conjunction with updrafts in supercells. Tornadoes sometimes form in mesocyclones. Persistent mesocyclones that have significant vertical extent are detected by Doppler radar as mesocyclone signatures. Tornado warnings may be issued when a mesocyclone signature is detected.
Mesocyclone signature-
The Doppler velocity pattern of a mesocyclone within a severe thunderstorm. In a storm relative reference frame, the idealized signature is symmetric about the radar viewing direction with marked azimuthal shear across the core region between peak Doppler velocity values of opposite sign. Typical signatures consist of Doppler velocity differences of 25to 75 ms pow minus1 across core diameters of 2to8 km, with resulting azimuthal shear values of 5 / 1000 per s to 2 / 100 per s.
Mesojet-
A mesoscale wind maximum. It typically may have an along flow length scale of tens to hundreds of kilometers and a cross flow length scale of less than 100 km. Mesojets differ from planetary scale jets, which can have length scales of several thousand kilometers, and synoptic scale jets, which may have length scales of 1000to2000 km and are commonly found in association with progressive synoptic scale troughs and ridges. Larger mesojets may also sometimes be known as jet streaks. Mesojets can form adjacent to prominent orographic features in association with terrain channeled flow. Mesojets are also seen in association with organized mesocale convective systems as typified by the evaporatively driven rear inflow jet commonly found behind active squall lines lines. Mesojets may also be found in conjunction with prominent lower tropospheric stable layers where the airflow can become decoupled from the planetary boundary layer, especially at night. An exceptionally well organized lower tropospheric mesojet extending over hundreds of kilometers might be known as a low level jet.
Mesolow-
A low pressure area on the mesoscale. It has been used to refer both to features observed within convective storms and features even larger in scale.
Mesopause-
The top of the mesosphere and the base of the thermosphere. The mesopause is usually located at heights of 85 to 95 km, and is the site of the coldest temperatures in the atmosphere. Temperatures as low as 100 K (minus 173 degree C) have been measured at the mesopause by rockets. See atmospheric shell.
Mesoscale-
Pertaining to atmospheric phenomena having horizontal scales ranging from a few to several hundred kilometers, including thunderstorms, squall lines, fronts, precipitation bands in tropical and extratropical cyclones, and topographically generated weather systems such as mountain waves and sea and land breezes. From a dynamical perspective, this term pertains to processes with timescales ranging from the inverse of the Brunt Vaisala frequency to a pendulum day, encompassing deep moist convection and the full spectrum of inertio gravity waves but stopping short of synoptic scale phenomena, which have Rossby numbers less than 1.
Mesoscale cellular convection-
A regular pattern of convective cells that can develop in an atmospheric boundary layer heated from below or radiatively cooled from cloud top. This phenomenon is readily observed in satellite imagery during cold air outbreaks when continental air passes over the relatively warm coastal ocean. Cloud lines, marking horizontal roll vortices, form initially in the developing marine atmospheric boundary layer. These lines evolve into open cells, which are defined by clouds in the upward motion along the edges of honeycomb shaped cells, with less cloudy subsiding air in their centers. The convective structure further evolves into closed cells, which have cloudy centers and cloud free edges.
Mesoscale convective complex-
A subset of mesoscale convective systems (MCS) that exhibit a large, circular (as observed by satellite), long lived, cold cloud shield. Alternatively, a dynamical definition of an MCC requires that the system have a Rossby number of order 1 and exhibit a horizontal scale comparable to the Rossby radius of deformation. In midlatitude MCS environments, the Rossby radius of deformation is about 300 km.
Mesoscale convective system-
A cloud system that occurs in connection with an ensemble of thunderstorms and produces a contiguous precipitation area on the order of 100 km or more in horizontal scale in at least one direction. An MCS exhibits deep, moist convective overturning contiguous with or embedded within a mesoscale vertical circulation that is at least partially driven by the convective overturning.
Mesoscale disturbance-
Same as disturbance except that the atmospheric feature has a Rossby number of order 1 and exhibits a horizontal scale comparable to the Rossby radius of deformation. For such systems, both ageostrophic advection and rotational influences are important.
Mesoscale eddies-
In oceanography, densely packed, irregularly oval shaped high and low pressure centers roughly 400 km (240 miles) in diameter in which current intensities are typically tenfold greater than the local means.
Microclimate-
The fine climatic structure of the air space that extends from the very surface of the earth to a height where the effects of the immediate character of the underlying surface no longer can be distinguished from the general local climate (mesoclimate or macroclimate). The microclimate varies with and in turn is superimposed upon the larger scale conditions. While some rigid limits have been placed on the thickness of the layer concerned, it is more realistic to consider variable thicknesses. (Observe the microclimate of a putting green versus that of a redwood forest.) Generally, four times the height of surface growth or structures defines the level where microclimatic overtones disappear. Microclimate can be subdivided into as many different classes as there are types of underlying surface. With sufficient detail, this could be almost limitless. Currently, the most studied broad types are the urban microclimate, affected by pavement, buildings, air pollution, dense inhabitation, etc., the vegetation microclimate, concerned with the complex nature of the air space occupied by vegetation, and its effects upon the vegetation (see phytoclimatology); and the microclimate of confined spaces (the cryptoclimate) of houses, greenhouses, caves, etc.
Microfront-
A sharp horizontal temperature contrast of a few degrees Celsius within a width of tens of centimeters to a few meters along the trailing edge of a thermal plume in the surface layer of the atmospheric boundary layer.
Microlayer-
1. A thin interface between two other layers. 2. The very thin (order of 1 mm) layer of air adjacent to the surface for which molecular transport (conduction, diffusion, viscosity) dominates over turbulent transport.
Miejour-
A warm, moist sea breeze from the south that sets in at midday in Provence, France, south of Mount Ventoux. In the Roussillon region the midday south wind (mitgjorn) is irregular and generally light, and is dry after crossing the Pyrenees.
Mini supercell-
Convective storm that contains similar radar characteristics to those of a supercell (e.g., hook echo, WER, BWER), but is significantly smaller in height and width. The diameter of the radar detected rotation is 1 to 8 km. This is a relatively new storm type, the existence of which has been confirmed by data from the recently installed WSR 88D radars in the United States. Mini supercells occur in areas where the height of the equilibrium level is low, most often in the northern United States, but possibly under certain weather conditions in any area of the world. They are sometimes found in landfalling tropical cyclones.
Minor ridge-
A ridge of smaller scale than a long wave ridge. It ordinarily moves rapidly and is associated with a migratory anticyclonic disturbance in the lower troposphere.
Minor trough-
A pressure trough of smaller scale than a long wave trough. It ordinarily moves rapidly and is associated with a migratory cyclonic disturbance in the lower troposphere.
Mistral-
North wind that blows down the Rhone valley south of Valence, France, and into the Gulf of Lions. It is strong, squally, cold, and dry, the combined result of the basic circulation, a fall wind, and jet effect wind. It blows from the north or northwest in the Rhone Delta, where it is strongest, from northwest in Provence and from northeast in the valley of the Durance below Sisteron. A general mistral usually begins with the development of a depression over the Tyrrhenian Sea or Gulf of Genoa with an anticyclone advancing from the Azores to central France. It often exceeds 27 m per s (60 mph) and reaches 38 m per s (85 mph) in the lower Rhône valley and 22 m per s (50 mph) at Marseilles, decreasing both east and west and out to sea. It remains strong to a height of 2 to 3 km. In the absence of a strong pressure gradient, a weaker katabatic local mistral develops in the Rhône valley. A general mistral usually lasts for several days, sometimes with short lulls. It is most violent in winter and spring, and may do considerable damage. Market gardens and orchards are protected from it by windbreaks, and rural houses are built with only a few openings on the side exposed to it. The mistral has a variety of local names: mangofango in Provence; secaire, maistrau, maistre, or magistral in Cévennes; dramundan in Perpignan; cierzo in Spain; cers in the Pyrenees, etc. South of Mont Ventoux a similar wind is named bise. A local west wind of mistral type that descends from Mt. Canigou to the plains of Roussillon is called canigonenc. Compare bora, tramontana, maestro; see also cavaliers.
Mixed cloud-
A cloud containing both water drops (supercooled at temperatures below 0 degree C) and ice crystals, hence a cloud with a composition between that of a water cloud and that of an ice crystal cloud.
Mixed layer-
A type of atmospheric boundary layer characterized by vigorous turbulence tending to stir and uniformly mix, primarily in the vertical, quantities such as conservative tracer concentrations, potential temperature, and momentum or wind speed.
Mixed layer capping inversion-
The statically stable layer of air at the top of the atmospheric boundary layer. Because the troposphere is statically stable on the average (i.e., potential temperature increases with height), and because turbulence in the boundary layer causes potential temperatures to become somewhat well mixed there, conservation of heat requires that there be a potential temperature increase (i.e., a temperature step or inversion) at the top of the boundary layer. It is this inversion that separates the boundary layer from the rest of the troposphere by limiting the domain of turbulence. It is also responsible for trapping pollutants near the ground during fair weather.
Mixed layer depth-
The thickness, zi, of the mixed layer, defined as the location of a capping temperature inversion or statically stable layer of air. Often associated with, or measured by, a sharp increase of potential temperature with height, a sharp decrease of water vapor mixing ratio, a sharp decrease in turbulence intensity, a sharp decrease in pollutant concentration, a change of wind speed to geostrophic, a minimum of turbulent heat flux, and a maximum of signal intensity from remote sensors such as sodars and wind profilers. Quite variable in space and time, the mixed layer depth typically increases during fair weather daytime over land from tens of meters shortly after sunrise to 1 to 4 km before sunset, depending on the location and season.
Mixed layer evolution-
The three part change of the atmospheric boundary layer that typically occurs during fair weather over land on sunny days. In the early morning, the mixed layer is shallow, slowly deepening, cool (in a potential temperature sense), and is capped by the remains of the stable boundary layer from the previous night. In mid to late morning, the top of the mixed layer exhibits rapid rise as heating eliminates the nocturnal inversion, and the mixed layer grows through the residual layer. The third stage in late morning and afternoon is that of a deep (order of 1 to 2 km) convective boundary layer of relatively constant depth.
Mixed layer venting-
Removal of pollutants out of the top of the atmospheric boundary layer through the mixed layer capping inversion. Normally pollutants cannot escape through the capping inversion. However, penetrating cumulus clouds, thunderstorms, mountain circulations, and frontal circulations can force polluted air through the inversion to vent pollutants into the free atmosphere.
Mixing cloud-
A cloud formed when two subsaturated volumes of moist air with different temperatures and vapor pressures mix isobarically and adiabatically to form a volume of moist air with an intermediate temperature and vapor pressure above the saturation value at that temperature.
Mixing fog-
Fog, light and of short duration, produced by the mixing of two moist but nonsaturated air masses with different temperatures.
Moazagotl-
A stationary bank of cirriform cloud marking the upper portion of the system of lenticular clouds formed in the lee wave produced by flow across the Sudeten Mountains in southeastern Germany; a type of foehn cloud.
Moazagotl wind-
The strong wind blowing across a mountain crest, responsible for the formation of the Moazagotl cloud.
Moderate breeze-
In the Beaufort wind scale, a wind with a speed from 11 to 16 knots (13 to 18 mph) or Beaufort Number 4 (Force 4).
Moderate gale-
In the Beaufort wind scale, a wind with a speed from 28 to 33 knots (32 to 38 mph) or Beaufort Number 7 (Force 7).
Moist air-
1. In atmospheric thermodynamics, air that is a mixture of dry air and any amount of water vapor. Compare dry air, saturation. 2. Generally, air with a high relative humidity.
Moist convection-
Atmospheric convection in which the phase changes of water play an appreciable role. All cumuliform clouds are manifestations of moist convection. The enthalpy exchange between condensing water vapor or freezing liquid water and air (see latent heat) is a major contributor to the positive buoyancy of updrafts, while the reverse exchange between air and evaporating water or melting ice contributes strongly to the negative buoyancy of downdrafts.
Moist tongue-
An extension or protrusion of moist air into a region of lower moisture content. Cloudiness and precipitation are closely related to moist tongues.
Moisture-
In meteorology, a general term usually referring to the water vapor content of the atmosphere, or to the total water substance (gaseous, liquid, and solid) present in a given volume of air.
Moisture pooling-
The development of an area in the boundary layer (e.g., often observed on surface or 850 mb charts) where moisture values become higher than in the surrounding region. Moisture pooling typically occurs in an area of low level convergence during the warm (growing) season, and can have a significant effect on convection initiation and evolution.
Molan-
Breeze blowing from Arve toward Geneva in Switzerland.
Monsoon-
A name for seasonal winds. It was first applied to the winds over the Arabian Sea, which blow for six months from northeast and for six months from southwest, but it has been extended to similar winds in other parts of the world. Even in Europe the prevailing west to northwest winds of summer have been called the European monsoon. The primary cause is the much greater annual variation of temperature over large land areas compared with neighboring ocean surfaces, causing an excess of pressure over the continents in winter and a deficit in summer, but other factors such as the relief features of the land have a considerable effect. The monsoons are strongest on the southern and eastern sides of Asia, the largest landmass, but monsoons also occur on the coasts of tropical regions wherever the planetary circulation is not strong enough to inhibit them. They have been described in Spain, northern Australia, Africa except the Mediterranean, Texas, and the western coasts of the United States and Chile. In India the term is popularly applied chiefly to the southwest monsoon and, by extension, to the rains which it brings. See brisa, elephanta; compare etesians, meltem.
Monsoon depression-
A depression that forms within the monsoon trough. The term is most frequently used to describe weak cyclonic disturbances that form over the Bay of Bengal and generally track northwestward over the Indian subcontinent. These occasionally intensify into tropical cyclones if they remain over warm ocean water long enough. The term is also used to describe depressions that form within the monsoon trough near Australia and in the western North Pacific region. The term has gained ascendancy in use to refer to a broad tropical cyclonic vortex characterized by 1) its large size, where the outermost closed isobar may have a diameter on the order of 600 n mi (1000 km); 2) a loosely organized cluster of deep convective elements, which may form an elongated band of deep convection in the east semicircle; 3) a low level wind distribution that features a 100 n mi (200 km) diameter light wind core, which may be surrounded by a band of gales or contain a highly asymmetric wind field; and 4) a lack of a distinct cloud system center. Most monsoon depressions that develop in the western North Pacific eventually acquire persistent central convection and accelerated core winds, marking their transitions into conventional tropical cyclones.
Monsoon fog-
An advection fog produced as a monsoon circulation that transports warm moist air over a colder surface.
Monsoon gyre-
A convection of the summer monsoon circulation of the western North Pacific characterized by 1) a very large nearly circular low level cyclonic vortex (not the result of the expanding wind field of a preexisting monsoon depression or tropical cyclone) that has an outermost closed isobar with a diameter on the order of 1200 n mi (2500 km); 2) a cloud band bordering the southern through eastern periphery of the vortex/surface low; and 3) a relatively long (two week) life span. Initially, a subsequent regime exists in its core and western and northwestern quadrants with light winds and scattered low cumulus clouds; later, the area within the outer closed isobar may fill with deep convective cloud and become a isobar or tropical cyclone. Note: a series of midget tropical cyclones may emerge from the head or leading edge of the peripheral tropical cyclone of a monsoon gyre.
Monsoon low-
A seasonal low found over a continent in the summer and over the adjacent sea in the winter. Examples are the lows over the southwestern United States and India in summer and those located off lower California and in the Bay of Bengal in winter. Palmer (1951) points out that, while the winter and summer monsoon lows appear similar on mean charts, they are dynamically quite different. Compare thermal low.
Monsoon surge-
The temporary extension of deep monsoon flow into a region not normally dominated by persistent monsoon flow. This temporary extension or surge may last from a few days to three weeks. These surges most commonly occur eastward across the Philippine Sea into the western North Pacific and east of Australia into the western South Pacific. The establishment of a reverse oriented monsoon trough is accompanied by an eastward surge in the monsoon flow. Monsoon surges are often precursors to the development of tropical cyclones.
Morget-
The night land breeze on Lake Geneva, Switzerland.It blows from the north from 5 to 7 P.M. until 7 to 9 A.M. as a poweful breeze.In the late fall and winter it blows almost throughout the day.
Mountain breeze-
A nocturnal component of the mountain plains or mountain valley wind systems encountered during periods of light synoptic flow.
Mountain fog-
Fog formed by orographic lifting to condensation of moist air up a mountain slope.
Mountain gap wind-
A local wind blowing through a gap between mountains, a gap wind. This term was introduced by R. S. Scorer (1952) for the surface winds blowing through the Strait of Gibraltar. When air stratification is stable, as it usually is in summer, the air tends to flow through the gap from high to low pressure, emerging as a jet with large standing eddies in the lee of the gap. The excess of pressure on the upwind side is attributed to a pool of cold air held up by the mountains. Similar winds occur at other gaps in mountain ranges, such as the tehuantepecer and the jochwinde, and in long channels, such as the Strait of Juan de Fuca between the Olympic Mountains of Washington and Vancouver Island, British Columbia. Compare jet effect wind, canyon wind, mountain wind.
Mountin plain wind systems-
The diurnal cycle of local winds between a mountain or a mountain range and the adjacent or surrounding plains during periods of weak synoptic flow.
Mountin valley wind systems-
The diurnal cycle of local winds in a mountain valley during clear or mostly clear periods of weak synoptic flow.
Mountain wave-
An atmospheric gravity wave, formed when stable air flow passes over a mountain or mountain barrier.
Mountain wave cloud-
A cloud that forms in the rising branches of mountain waves and occupies the crests of the waves. The most distinctive are the sharp edged, lens , or almond shaped lenticular clouds, but a variety of stratocumulus, altocumulus, and cirrocumulus forms appear in both the main, vertically propagating waves and in the lee waves. See mountain wave, foehn cloud.
Mountain wind-
A nocturnal, thermally forced wind from the direction of the mountains, generated by cooling along the mountain slopes; a downvalley wind, or the nighttime downslope (katabatic) component of a mountain plains wind system.
Multicell convective storm-
A convective storm system usually composed of a cluster of ordinary convective cells at various stages of their life cycle. New cells within the convective system are generated primarily by either low level convergence along a preexisting boundary, or by lifting at the leading edge of the system scale cold pool that was produced by the previous cells. A multicell storm may have a lifetime of several hours, and may also have supercells incorporated as a part of the system as well. See also cell, ordinary cell, supercell, thunderstorm.
Munk boundary layer-
A horizontal boundary layer in which lateral transport of momentum exerts a torque on fluid parcels, thereby allowing them to cross isolines of background potential vorticity. In many ocean general circulation models, the western boundary currents are Munk boundary layers.
