Glossary of meteorology
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This glossary of meteorology is a list of terms and concepts relevant to meteorology and the atmospheric sciences, their sub-disciplines, and related fields.
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A[edit]
- advection
- The horizontal transport of some property of the atmosphere or ocean, such as thermal energy, humidity, or salinity. In the context of meteorology, the related term convection generally refers to vertical transport.
- actinoform
- actinometer
- adiabatic process
- Any idealized hypothetical process by which energy is transferred between a thermodynamic system and its surroundings only as work, without a corresponding transfer of heat or mass. In the context of meteorology, the assumption of adiabatic isolation is often used to explain the processes of adiabatic heating and adiabatic cooling, which involve changes in temperature as a parcel of air is compressed or expanded by interaction with its surroundings.
- aerobiology
- aerography
- The production of weather charts.
- aeronomy
- The branch of meteorology that studies the upper regions of the Earth's or other planetary atmospheres, specifically their atmospheric motions, chemical compositions and properties, and interactions with the other parts of the atmosphere and with space.
- aerosol
- A suspension of fine solid particles or liquid droplets in air or another gas. Examples of natural aerosols include mist, clouds, fog, and dust.
- ageostrophy
- air mass
- A volume of air defined by its temperature and content of water vapor.
- air-mass thunderstorm
- air parcel
- In fluid dynamics, any amount of air that remains identifiable throughout its dynamic history while moving with an associated air flow.
- Alberta clipper
- almanac
- An annual publication of calendar events.
- altocumulus castellanus
- altocumulus
- altostratus
- American Meteorological Society (AMS)
- anabatic wind
- anemometer
- A scientific instrument used to measure wind speed.
- annular tropical cyclone
- anticyclone
- anticyclonic rotation
- anticyclonic tornado
- anticyclogenesis
- arcus cloud
- Arctic cyclone
- Atlantic hurricane
- atmosphere
- The various layers of gases surrounding the Earth and held in place by gravity. The Earth's atmosphere is the origin of the weather phenomena studied in meteorology. Atmospheric composition, temperature, and pressure vary across a series of distinct sublayers including the troposphere and stratosphere.
- atmospheric circulation
- atmospheric convection
- atmospheric density
- atmospheric pressure
- atmospheric sciences
- The collective of scientific disciplines that studies the Earth's atmosphere and its processes, including the effects other systems have on the atmosphere and those the atmosphere has on other systems. Meteorology and climatology are sub-disciplines.
- atmospheric sounding
- A measurement of the vertical distribution of physical properties through an atmospheric column, usually including pressure, temperature, wind speed and direction, moisture content, ozone concentration, and pollution, among others.
- atmospheric tide
- autumn
- avalanche
- Aviation Area Forecast (FA or ARFOR)
- A former message product of the U.S. National Weather Service issued to provide information to pilots and aviation routes about weather conditions across a large regional area within the United States. FAs were issued three times daily, valid for 18 hours and covered an area the size of several states. They were replaced by Graphic Area Forecasts (GFAs) in 2017.
B[edit]
- backscatter
- ball lightning
- barbs
- barograph
- A scientific instrument used to measure and record changes in atmospheric pressure over time.
- baroclinity
- barotropity
- barometer
- A scientific instrument used to measure atmospheric pressure.
- Beaufort scale
- Bernoulli's principle
- Bishop's ring
- black ice
- blizzard
- A severe snowstorm characterized by strong sustained winds of at least 35 miles per hour (56 km/h) and typically lasting three hours or more. They can have an immense size, covering hundreds or thousands of square miles, and occur most often in temperate, polar, or mountainous regions during the winter.
- blowing dust or sand
- blowing snow
- bounded weak echo region (BWER)
- bow echo
- A characteristic radar return from a mesoscale convective system that is shaped like an archer's bow and usually associated with squall lines or lines of convective thunderstorms. The distinct bow shape is a result of the focusing of a strong flow at the rear of the system. Especially strong bow echoes may develop into derechos.
- breeze
- Bulk Richardson Number (BRN)
- A dimensionless ratio related to the consumption of turbulence divided by the shear production of turbulence (the generation of kinetic energy caused by wind shear). It is an approximation of the Gradient Richardson Number.
- buoyancy
- bushfire
- Buys Ballot's law
C[edit]
- Canadian Meteorological and Oceanographic Society (CMOS)
- The national society of individuals and organizations dedicated to advancing atmospheric and oceanic sciences and related environmental disciplines in Canada, officially constituted in 1967.
- Canadian Meteorological Centre (CMC)
- capping inversion
- castellanus
- A cloud species that displays at least in its upper part cumuliform protuberances resembling the turrets of a castle, giving a crenellated aspect.
- ceiling
- ceiling balloon
- ceiling projector
- ceilometer
- Center for Analysis and Prediction of Storms (CAPS)
- chinook wind
- cirrocumulus
- cirrostratus
- cirrus
- clear ice
- A type of solid precipitation which forms when relatively large drops of water are supercooled into a dense, transparent coating of ice without air or other impurities. It is similar to glaze and hard rime and, when formed on the ground, is often called black ice.
- clear-air turbulence
- climate
- The statistics of weather in a given region over long periods of time, measured by assessing long-term patterns of variation in temperature, atmospheric pressure, humidity, wind, precipitation, and other meteorological variables. The climate of a particular location is generated by the interactions of the atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere and strongly influenced by latitude, altitude, and local topography. Climates are often classified according to the averages or typical ranges of different variables, most commonly temperature and precipitation.
- climatology
- A branch of the atmospheric sciences that studies climate, defined as weather conditions averaged over an extended to indefinite period of time. Climatology incorporates aspects of oceanography, geology, biogeochemistry, and the related field of meteorology to understand the long-term dynamics of climate-influencing phenomena and to produce climate models which can be used to estimate past climates and predict future climates.
- cloud
- An aerosol consisting of a visible mass of minute liquid droplets, frozen crystals or other particles suspended in the atmosphere. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of the saturation of an air mass when it is cooled to its dew point or when it gains sufficient moisture (usually in the form of water vapor) from an adjacent source to raise the dew point to the ambient temperature. There are many different types of clouds, which are classified and named according to their shape and altitude.
- cloud atlas
- cloud base
- The lowest altitude of the visible portion of a cloud.
- cloud drop effective radius
- cloud iridescence
- cloud species
- Any of a set of 14 Latin terms used to describe the shape and internal structure of tropospheric clouds. Cloud species are subdivisions of cloud genera and are themselves further subdivided into cloud varieties.
- cloud tag
- cloud type
- Any of a set of Latin names used to classify and identify clouds occurring in the troposphere, typically by characteristics such as their altitude, shape, and convective activity. A set of 10 or 12 traditional cloud types defined by the World Meteorological Organization and further subdivided into cloud species and cloud varieties is widely used in meteorology. Other classification systems have proposed many additional types.
- cloudburst
- coastal flooding
- col
- The point of intersection of a trough and a ridge in the pressure pattern of a weather map. It generally takes the shape of a saddle in which the air pressure is slightly higher than that within the low-pressure regions but still lower than that within the anticyclonic zones.
- cold front
- cold wave
- cold-core low
- Colorado low
- A type of low-pressure area that forms in southeastern Colorado or northeastern New Mexico, in the United States, and then proceeds to move east across the Great Plains, often producing heavy snow and ice when occurring in the winter.
- convection
- See atmospheric convection.
- convective available potential energy (CAPE)
- convective condensation level
- convective inhibition (CIN)
- convective instability
- convective outlooks
- convective storm detection
- convergence
- convergence zone
- corona
- crepuscular rays
- crosswind
- Crow instability
- An inviscid line-vortex instability most commonly observed in the skies behind large aircraft such as the Boeing 747. It occurs when the wingtip vortices interact with contrails from the engines, producing characteristic visual distortions in the shapes of the contrails.
- cumulonimbus
- cumulus
- cumulus congestus
- cumulus humilis
- cumulus mediocris
- cyclone
- Any large-scale air mass characterized by inward spiraling winds which rotate around a strong center of low atmospheric pressure. Cyclones can form over land or water, can vary in size from mesocyclones such as tornadoes to synoptic-scale phenomena such as tropical cyclones and polar vortices, and may transition between tropical, subtropical, and extratropical phases.
- cyclonic rotation
- cyclogenesis
D[edit]
- dark adaptor goggles
- A type of specialized eyewear used by meteorologists and astronomers for adapting the eyes to the dark prior to an observation made at night, or for aiding with identification of clouds during bright sunshine or when there is a glare from snow.
- dawn
- daytime
- The period of the day between sunrise and sunset, during which any given point on the Earth experiences natural illumination from especially direct sunlight, known as daylight.
- dBZ
- debris cloud
- deformation
- The rate of change of shape of a fluid body such as an air mass. This quantity is very important in the formation of atmospheric fronts, in the explanation of cloud shapes and in the diffusion of materials and properties through the atmosphere.
- dense fog
- depression
- See low-pressure area.
- derecho
- detention basin
- detention dam
- dew
- dew point
- (Td)
- dew point depression
- Diablo wind
- diamond dust
- divergence
- diffluence
- diffuse sky radiation
- disdrometer
- A scientific instrument used to measure the size distribution and velocity of falling hydrometeors such as raindrops.
- diurnal temperature variation
- Dobson unit
- doldrums
- Doppler on Wheels (DOW)
- Doppler weather radar
- downburst
- downdraft
- drifting snow
- drizzle
- drought
- dry lightning
- Lightning associated with a dry thunderstorm.
- dry line
- dry microburst
- dry punch
- dry season
- dry thunderstorm
- A thunderstorm that produces thunder and lightning but in which most or all of its precipitation evaporates before reaching the ground. Dry thunderstorms occur necessarily in dry conditions, and their lightning strikes, sometimes referred to as dry lightning, are a major cause of wildfires.
- DSD
- dual polarization weather radar
- dusk
- dust devil
- dust storm
E[edit]
- eddy
- Ekman layer
- The layer in a fluid in which there is a force balance between the pressure-gradient force, the Coriolis force, and turbulent drag. Ekman layers occur in both the atmosphere and the ocean.
- Ekman number
- Ekman spiral
- Ekman transport
- energy-helicity index (EHI)
- El Niño
- El Niño–Southern Oscillation
- emagram
- One of four thermodynamic diagrams used to display temperature lapse rate and moisture content profiles in the atmosphere. Emagrams have axes of temperature (T) and pressure (p). Temperature and dew point data from radiosondes are plotted on these diagrams to allow calculations of convective stability or convective available potential energy.
- Enhanced Fujita scale (EF scale)
- entrainment
- Environment and Climate Change Canada
- Environmental Modeling Center (EMC)
- Environmental Research Laboratories (ERL)
- Environmental Science Services Administration (ESSA)
- The predecessor agency (1965–1970) to the National Oceanic and Atmospheric Administration (1970–present).
- equivalent temperature ()
- equivalent potential temperature ()
- Eulerian equations
- European windstorm
- explosive cyclogenesis
- extratropical cyclone
- extreme weather
- Any weather that is unexpected, unusual, unpredictable, unseasonal, or especially severe (i.e. weather at the extremes of an historical distribution).
- eye
F[edit]
- fall wind
- See katabatic wind.
- Fata Morgana
- fetch
- field mill
- fire whirl
- firestorm
- flash flood
- Any flood which very rapidly inundates low-lying areas such as washes, rivers, dry lakes, and basins, especially one which recedes again in less than six hours. Flash flooding can be caused by heavy rain associated with severe weather, large amounts of meltwater from melting ice or snow, or the sudden collapse of a natural ice or debris dam.
- flash freezing
- flood
- An overflow of water which submerges land that is usually dry. Flooding may occur when water bodies such as rivers, lakes, or oceans escape their boundaries by overtopping or puncturing levees, or it may occur when precipitation accumulates on saturated ground more rapidly than it can either infiltrate or run off.
- flumen
- fog
- A visible aerosol of minute water droplets or ice crystals that is suspended in the air at or near the Earth's surface. Fog is often considered a type of low-lying cloud and is heavily influenced by local topography, nearby bodies of water, and wind conditions.
- fogbow
- föhn wind
- A type of warm, dry, downslope wind that occurs in the lee of a mountain range.
- forward-flank downdraft (FFD)
- fractus (Fr)
- frazil ice
- freezing drizzle
- freezing fog
- freshet
- freezing rain
- front
- A boundary separating two masses of air of different densities and usually also of different temperatures and humidities. Weather fronts are the principal cause of meteorological phenomena outside the tropics, often bringing with them clouds, precipitation, and changes in wind speed and direction as they move. Types of fronts include cold fronts, warm fronts, and occluded fronts.
- frontogenesis
- frontolysis
- frost
- Fujita scale (F scale)
- funnel cloud
G[edit]
- gale
- A strong surface wind, typically used as a descriptor in nautical contexts. Gales are variably defined based on their speed; in the modern Beaufort scale, sustained winds of 28–33 knots (52–61 km/h; 32–38 mph), Beaufort number 7, are designated as near gales and those of 34–47 knots (63–87 km/h; 39–54 mph), spanning Beaufort numbers 8 and 9, as gales.
- gale warning
- gap wind
- geopotential height
- geostrophic wind
- The theoretical wind that would result from an exact balance between the Coriolis force and the pressure gradient force (known as geostrophic balance). The true wind almost always differs from the geostrophic wind due to the influence of other forces such as friction from the ground.
- glaze
- GPS meteorology
- graupel
- A type of precipitation that forms when supercooled water droplets are collected and freeze on falling snowflakes, forming balls of rime 2–5 mm (0.079–0.197 in) in diameter. Graupel is distinct from hail, small hail, and ice pellets.
- grease ice
- green flash
- Greenwich Mean Time (GMT)
- ground blizzard
- ground truth
- Information, such as local weather conditions, provided by direct observation (i.e. empirical evidence) as opposed to information provided by inference.
- gust
- gust front
- gustnado
H[edit]
- haboob
- hail
- A type of solid precipitation that consists of balls or irregular lumps of ice usually 5–150 mm (0.20–5.91 in) in diameter, each of which is called a hailstone. Hail formation requires environments with strong, upward motion of air and low altitudes at which water freezes, which makes it possible within most thunderstorms. It is distinct from graupel and sleet or ice pellets.
- hailstorm
- Haines Index
- halo
- hard rime
- Harmattan
- haze
- hazardous seas warning
- hazardous seas watch
- heat burst
- heat index (HI)
- A meteorological index that posits the apparent temperature perceived by the average human being who is exposed to a given combination of air temperature and relative humidity in a shaded area. For example, when the air temperature is 32 °C (90 °F) with 70% relative humidity, the heat index is 41 °C (106 °F).
- heat lightning
- heat wave
- heavy snow warning
- A type of weather warning formerly issued by the U.S. National Weather Service to alert areas in which a high rate of snowfall (generally 6 inches (15 cm) or more in 12 hours) was occurring or was forecast. The warning was replaced by the Winter Storm Warning for Heavy Snow beginning with the 2008–09 winter storm season.
- helicity
- high-pressure area
- hodograph
- hook echo
- horseshoe vortex
- humidity
- A measure of the amount of water vapor present in a parcel of air. By quantifying the saturation of the air with moisture, humidity indicates the likelihood of precipitation, dew or fog occurring. The amount of water vapor needed to achieve full saturation increases as the air temperature increases. Three primary measurements of humidity are widely employed in meteorology: absolute, relative, and specific.
- humidex
- humilis
- hurricane
- The local name for a tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean.
- hurricane hunters
- huayco
- hydrometeor
- Any particulate of liquid or solid water within the atmosphere, encompassing all types of precipitation, formations due to condensation such as clouds and haze, and particles blown from the Earth's surface by wind such as blowing snow and sea spray.
- hydrometeorology
- hydrosphere
- The combined mass of all solid, liquid, and gaseous forms of water found on, beneath, or above the surface of the Earth, including all oceans, lakes, streams, groundwater, atmospheric water vapor, snow, ice caps, and glaciers.
- hydrostatic equilibrium
- hygrometer
- A scientific instrument used to measure humidity.
- hypsometer
- hygroscopy
I[edit]
- ice
- Water frozen into a solid state. Ice is abundant on Earth's surface and in the atmosphere and plays a major role in Earth's water cycle and climate. Its natural occurrence in weather phenomena takes many forms, including snowflakes, hail, frost, icicles and ice spikes.
- iceberg
- ice accretion indicator
- ice crystals
- ice fog
- ice pellets
- ice spike
- ice storm
- icicle
- A long, slender spike of ice formed when water dripping or falling from an object freezes.
- ideal gas law
- in situ
- incus
- Indian summer
- inflow
- instrument flight rules (IFR)
- International Standard Atmosphere
- irisation
- See cloud iridescence.
J[edit]
- jet stream
- A narrow, fast-flowing, meandering air current primarily occurring in the upper part of the troposphere, at altitudes above 9 kilometres (30,000 ft), and usually flowing from west to east. The Northern and Southern Hemispheres each have a polar jet and a subtropical jet; low-level jets and other types of jet streams can form under certain conditions.
K[edit]
- K-index
- katabatic wind
- A wind that carries high-density air from a higher elevation down a slope under the force of gravity, usually at speeds of the order of 10 knots (19 km/h) or less but occasionally at much higher speeds.
- Kelvin temperature scale
- Kelvin–Helmholtz instability
- khamsin
- kinematics
- A branch of classical mechanics that describes the motion of points, bodies, and systems of bodies without considering the forces that caused the motion.
- Köppen climate classification
L[edit]
- Lagrangian equations
- La Niña
- lake-effect snow
- A weather phenomenon produced when a cold air mass moves across long expanses of warmer lake water, which causes the lowest layers of air to pick up warm water vapor from the lake, rise through the upper layers, freeze and then precipitate on the lake's leeward shores. In combination with orographic lift, the effect produces narrow but very intense bands of precipitation, especially snow, which can deposit at very high rates and result in very large amounts of snowfall over a region. The same effect can also occur over bodies of salt water, when it is termed ocean-effect or bay-effect snow.
- land breeze
- landfall
- landslide
- landspout
- A type of tornado emerging from a parent cloud that does not contain a pre-existing mid-level mesocyclone or other rotation. Landspouts share a development process and resemblance with waterspouts. They are generally smaller and weaker than supercell tornadoes and are rarely detected by Doppler weather radar.
- lapse rate
- lee trough
- lee wave
- Lemon technique
- A method used by meteorologists which focuses on updrafts and uses weather radar to determine the relative strength of thunderstorm cells in a vertically sheared environment.
- lenticular cloud
- level of free convection (LFC)
- Lidar
- A surveying method that measures the distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor; differences in laser return times and wavelengths can then be used to create digital three-dimensional representations of the target. The name is now used as an acronym of light detection and ranging.
- lifted condensation level (LCL)
- lifted index (LI)
- light pillar
- lightning
- lightning activity level
- lightning detection
- lightning strike
- line echo wave pattern (LEWP)
- low-level jet
- low-level windshear alert system
- low-pressure area (L)
- low-topped supercell (LT)
- lysimeter
M[edit]
- MAFOR
- A North American system used in the transmission of marine weather forecasts to compress large amounts of information about meteorological and marine conditions, including visibility, expected future wind speed and direction, the "state of sea", and the period of validity of the forecast, into shorter code for convenience during radio broadcasting. MAFOR is an abbreviation of MArine FORecast.
- marine cloud brightening
- marine stratocumulus
- mass flow
- The movement of a fluid, such as an air mass, down a pressure or temperature gradient.
- mesocyclone
- mesohigh
- mesolow
- mesonet
- mesoscale convective complex (MCC)
- mesoscale convective discussion (MCD)
- mesoscale convective system (MCS)
- mesoscale convective vortex (MCV)
- mesoscale meteorology
- mesosphere
- mesovortices
- METAR
- Météo-France
- meteorology
- A branch of the atmospheric sciences which seeks to understand and explain observable weather events, with a major focus on weather prediction. Meteorology uses variables familiar in atmospheric chemistry and atmospheric physics to describe and quantify meteorological phenomena, including temperature, pressure, water vapor, mass flow and how these properties interact and change over time.
- microburst
- micronet
- A weather observation network even denser than a mesonet, such as the Oklahoma City Micronet.
- microscale meteorology
- mini-supercell
- A distinct kind of supercell that is smaller than a typical supercell.
- mini-tornado
- A fallacious term often used in news media to refer to damaging winds accompanying a thunderstorm, indifferently caused by tornadoes or microburst, on a small area.
- misocyclone
- misoscale meteorology
- mixing ratio
- Modified Fujita Scale
- An update to the original Fujita scale from 1971 proposed by Ted Fujita in 1992.
- moisture convergence
- An area where moisture concentrates due to the air flow near the surface.
- mountain breeze
- mountain-gap wind
- multicellular thunderstorm
- multiple-vortex tornado
- moisture
- The presence of liquid, especially water, within a body or substance, often in trace amounts. Moisture in the air in the form of water vapor underlies the concept of humidity.
- monsoon
- Morning Glory cloud
- mudflow
- mudslide
N[edit]
- National Center for Atmospheric Research (NCAR)
- National Centers for Environmental Prediction (NCEP)
- National Hurricane Center (NHC)
- National Oceanic and Atmospheric Administration (NOAA)
- National Severe Storms Forecast Center (NSSFC)
- A predecessor forecasting center to the Storm Prediction Center that was located in Kansas City, Missouri.
- National Severe Storms Laboratory (NSSL)
- A NOAA lab in Norman, Oklahoma tasked with researching severe weather.
- National Tornado Database
- The official NOAA record of all known tornadoes within the United States from 1950 to present.
- National Weather Center (NWC)
- National Weather Service (NWS)
- National Weather Service Training Center (NWSTC)
- needle ice
- negative tilt
- nephelometer
- nephoscope
- A scientific instrument used to measure the altitude, direction, and velocity of atmospheric clouds.
- NEXRAD
- nimbostratus
- noctilucent cloud
- nor'easter
- A macro-scale extratropical cyclone, especially one which impacts the middle and north Atlantic coasts of North America. The name derives from the direction of the winds that most strongly affect the eastern seaboard between the months of October and March; accompanied by very heavy rain or snow, causing severe coastal flooding and hurricane-force winds.
- Novaya Zemlya effect
- nowcasting
- numerical weather prediction
O[edit]
- occluded front
- okta
- A unit of measurement used to describe the amount of cloud cover at a given location in terms of how many eighths of the sky are covered in clouds, ranging from 0 oktas (completely clear) to 8 (completely overcast) or sometimes 9 oktas (indicating that the sky is obstructed from view).
- omega equation
- opacity
- orographic cloud
- orographic precipitation
- overcast
- The condition of cloud clover wherein clouds obscure at least 95% of the sky. The type of cloud cover that qualifies as overcast is distinguished from obscuring surface-level phenomena such as fog.
- overshooting top
- OU-PRIME
- outflow
- outflow boundary
- outflow jet
- ozone depletion
- ozone layer
P[edit]
- paleoclimatology
- pan evaporation
- pancake ice
- A form of ice that consists of round, flat pieces of ice with elevated rims, diameters ranging from 30 centimetres (12 in) to 3 metres (9.8 ft), and thicknesses of up to 10 centimetres (3.9 in).
- pannus
- pampero
- parhelia
- See sun dog.
- partial pressure
- Particularly Dangerous Situation
- pascal (Pa)
- The SI derived unit of pressure, defined as one newton per square metre. In meteorology, measurements of atmospheric pressure are often given in kilopascals (kPa).
- Pascal's law
- Pearson scale
- A tornado rating scale developed by Allen Pearson differentiating path length (P) and path width (P) to accompany NOAA Fujita scale (F) ratings.
- permafrost
- photometeor
- Any bright object or other optical phenomenon appearing in the Earth's atmosphere when sunlight or moonlight creates a reflection, refraction, diffraction, or interference under particular circumstances. Common examples of photometeors include halos, rainbows, coronas, crepuscular rays, and sun dogs.
- Phi_DP ()
- pileus
- pilot balloon
- pilot report (PIREP)
- polar low
- polar mesospheric clouds
- polar stratospheric cloud
- polar vortex
- Either of the two very large, persistent, rotating, upper-level low-pressure areas suspended in the Earth's atmosphere near the geographic poles. The polar vortices predictably strengthen during their local winter and weaken during their local summer as the temperature contrast between the poles and the Equator changes. When either vortex is weak, high-pressure zones of lower latitudes may push poleward, driving the vortex, jet stream, and masses of cold, dry polar air into the mid-latitudes, which can cause sudden, dramatic drops in temperature known as cold waves.
- potential temperature ()
- potential vorticity
- power flash
- A sudden bright light caused when an overhead power line is severed or especially when a transformer explodes. Severe weather is one of the most common causes.
- precipitable water
- pressure gradient
- pressure gradient force (PGF)
- pressure system
- precipitation
- Any product of the condensation of atmospheric water vapor that falls by gravity, the main forms of which include rain, sleet, snow, hail, and graupel. Precipitation occurs when a portion of the atmosphere becomes locally saturated with water vapor such that the water condenses into liquid or solid droplets and thus "precipitates" out of the atmosphere.
- precipitation types
- prevailing winds
- psychrometer
- psychrometrics
- Pulse-Doppler radar
- pulse storm
- pyranometer
- A type of actinometer used to measure solar irradiance on a planar surface and solar flux density in the hemisphere above.
- pyrgeometer
- pyrheliometer
Q[edit]
- Q-vector
- quantitative precipitation estimation (QPE)
- A method of estimating the approximate amount of precipitation that has fallen at a location or across a region.
- quantitative precipitation forecast (QPF)
- The expected amount of melted precipitation accumulated over a specified time period within a specified area.
- quasi-geostrophic equations
- quasi-linear convective system (QLCS)
- quasistatic approximation
R[edit]
- radiation fog
- radiosonde
- A battery-powered scientific instrument released into the atmosphere, usually by a weather balloon, which measures various atmospheric parameters and transmits them by radio telemetry to a ground receiver. Radiosondes are essential sources of meteorological data, and hundreds are launched all over the world everyday.
- radius of maximum wind (RMW)
- rain
- A type of precipitation that occurs when liquid water in the form of droplets condenses from atmospheric water vapor, becoming heavy enough to fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth.
- rainbow
- raindrop size distribution
- rain and snow mixed
- rain gauge
- rain of animals
- rain shadow
- rain showers
- Short, intense periods of rainfall, especially when occurring in widely scattered locations.
- Rankine vortex
- rapid intensification
- rear flank downdraft (RFD)
- relative humidity
- remote sensing
- The acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation. In meteorology, satellite- or aircraft-based sensor technologies are widely used to detect and classify objects on the surface or within the atmosphere or oceans based on propagated electromagnetic signals.
- Rho_hv ()
- ridge
- rime
- A coating of ice on the surface of an object. See hard rime and soft rime.
- rogue wave
- roll cloud
- Rossby number
- Rossby wave
- rotation
- See cyclonic rotation.
S[edit]
- sandstorm
- See dust storm.
- sastrugi
- Sharp, irregular grooves or ridges formed on a snow surface by wind erosion, saltation of snow particles, and deposition, usually parallel to the prevailing winds. They are often found in the polar regions and in large, open areas such as frozen lakes in cold temperate regions.
- satellite tornado
- scud
- See pannus.
- sea breeze
- sea spray
- season
- Any division of the year marked by changes in weather, ecology and the duration of daylight. Seasons result from the Earth's orbit around the Sun and its axial tilt relative to the ecliptic plane. In temperate and polar regions, four calendar-based seasons – spring, summer, autumn and winter – are generally marked by significant changes in the intensity of sunlight that reaches the Earth's surface; these changes become less dramatic as one approaches the Equator, and so many tropical regions have only two or three seasons, such as a wet season and a dry season. In certain parts of the world, the term is also used to capture the timing of important ecological events, such as hurricane seasons, flood seasons and wildfire seasons.
- severe thunderstorm
- severe weather
- Any dangerous meteorological phenomena with the potential to cause damage on the ground surface, serious social disruption, or loss of human life. There are many types of severe weather, including strong winds, excessive precipitation, thunderstorms, tornadoes, tropical cyclones, blizzards, and wildfires. Some severe weather may be more or less typical of a given region during a given season; other phenomena may be atypical or unpredictable.
- shelf cloud
- shortwave trough
- SIGMET
- simoom
- single cell thunderstorm
- sirocco
- skew-T log-P diagram
- Skywarn
- The storm-spotting program of the U.S. National Weather Service. Skywarn organizations have also been formed in Europe and Canada.
- skipping tornado
- sleet
- slush
- snow
- A type of solid precipitation in the form of ice crystals which precipitate from the atmosphere and subsequently undergo changes on the Earth's surface. Snow occurs when snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals; upon reaching the ground it may then accumulate into snowpack or snowdrifts and, over time, metamorphose by sintering, sublimation, and freeze-thaw mechanisms. Unless the local climate is cold enough to maintain persistent snow cover on the ground, snow typically melts seasonally.
- snow gauge
- snow grains
- snow roller
- snowbelt
- snowdrift
- snowflake
- snowsquall
- snowstorm
- A type of winter storm accompanied particularly by heavy precipitation in the form of snow. Very large snowstorms with strong winds and meeting certain other criteria are called blizzards.
- SODAR
- solar irradiance
- solarimeter
- sounding
- See atmospheric sounding.
- sounding rocket
- specific humidity
- spindrift
- Sea spray blown from cresting waves during a gale. This spray "drifts" in the direction of the gale and is distinct enough that it is sometimes used to judge wind speed at sea.
- spring
- sprite
- squall line
- St. Elmo's fire
- standard atmosphere
- station model
- stationary front
- steam devil
- Stevenson screen
- storm
- Any disturbed state of an environment or atmosphere especially affecting the ground surface and strongly implying severe weather. Storms are characterized by significant disruptions to normal atmospheric conditions, which can result in strong wind, heavy precipitation, thunder and lightning (as with a thunderstorm), among other phenomena. They are created when a center of low pressure develops within a system of high pressure surrounding it.
- storm cell
- An air mass which contains up and down drafts in convective loops and which moves and reacts as a single entity. It functions as the smallest unit of a storm-producing weather system.
- storm chasing
- Storm Data and Unusual Weather Phenomena (SD)
- A National Climatic Data Center (NCDC) publication beginning in 1959 which details quality-controlled tornado and other severe weather summaries as the official NOAA record of such events.
- storm shelter
- storm spotting
- storm surge
- Storm Prediction Center (SPC)
- Storm Track
- straight-line wind
- stratocumulus
- stratosphere
- stratus
- summer
- Stüve diagram
- sun dog
- sunshine recorder
- sunshower
- A meteorological phenomenon in which rain falls while the sun is shining.
- supercell
- subtropical cyclone
- surface weather analysis
- surface weather observation
- sustained wind
- synoptic scale meteorology
T[edit]
- tail cloud
- A ragged band of cloud and/or fractus extending from a wall cloud toward the precipitation core.
- temperature
- A physical quantity expressing the thermal motion of a substance, such as a mass of air in the atmosphere, and proportional to the average kinetic energy of the random microscopic motions of the substance's constituent particles. Temperature is measured with a thermometer calibrated in one or more temperature scales: the Kelvin scale is the standard used in scientific contexts, but the Celsius and Fahrenheit scales are more commonly used in everyday contexts and for weather forecasting.
- temperature gradient
- temperature inversion
- tephigram
- terminal aerodrome forecast (TAF)
- Terminal Doppler Weather Radar (TDWR)
- thermal
- A column of rising air in the lower altitudes of the Earth's atmosphere. It is a form of atmospheric updraft created by the uneven heating of the Earth's surface by solar radiation, and an example of atmospheric convection.
- thermal wind
- thermo-hygrograph
- thermodynamics
- thermodynamic diagrams
- thermometer
- An instrument used to measure temperature or a temperature gradient.
- thermosphere
- thunder
- thundershower
- A relatively weak thunderstorm.
- thundersnow
- thunderstorm
- A storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Thunderstorms result from the rapid upward movement of warm, moist air, often along a front. They can develop in any geographic location but are most common in the mid-latitudes. They are usually accompanied by strong winds and heavy rain; especially strong or severe thunderstorms can produce some of the most dangerous weather phenomena, including large hail, downbursts, and tornadoes.
- thunderstorm asthma
- tilted updraft
- tornado
- A rapidly rotating column of air that is in contact with both a parent cloud and the surface of the Earth. Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensed funnel originating from the base of a cumulonimbus cloud, usually during a thunderstorm, with a cloud of rotating dust and debris beneath it. The most extreme tornadoes can achieve wind speeds of more than 300 miles per hour (480 km/h), span more than 2 miles (3.2 km) in diameter, and stay on the ground for dozens of miles (more than 100 km) before dissipating.
- Tornado Alley
- tornado climatology
- tornado debris signature (TDS)
- tornado emergency
- tornado family
- tornadogenesis
- tornado outbreak
- tornado outbreak sequence
- tornado preparedness
- tornado vortex signature (TVS)
- tornado warning
- tornado watch
- Tornado and Storm Research Organisation (TORRO)
- TORRO scale
- Totable Tornado Observatory (TOTO)
- training
- tropical cyclone
- A very large, rapidly rotating storm system characterized by a low-pressure center surrounded by a closed low-level atmospheric circulation, strong winds, and continuous spiral bands of thunderstorms that produce heavy rain. Tropical cyclones develop almost exclusively over and derive their strength from warm tropical seas. The strongest systems can last for more than a week, span more than 1,000 miles (1,600 km) in diameter, and cause significant damage to coastal regions with powerful winds, storm surges, and concentrated precipitation that leads to flooding. Depending on its location and strength, a tropical cyclone may be referred to by different names and categorized within a variety of classes.
- tropical cyclone scales
- tropical cyclogenesis
- tropical depression
- tropical disturbance
- tropical storm
- tropical wave
- tropics
- tropopause
- troposphere
- The lowest layer of the Earth's atmosphere, within which nearly all weather phenomena occur. The troposphere contains approximately 75% of the atmosphere's total mass and 99% of its water vapor and aerosols. The average height of the troposphere above the Earth's surface varies between 6 and 18 kilometres (3.7 and 11.2 mi) depending on latitude.
- trough
- trowal
- tsunami
- turbulence
- twilight
- 1. The indirect illumination of the lower atmosphere caused by the scattering of sunlight when the Sun itself is not directly visible because it is below the horizon.
- 2. The time period during which such illumination occurs, either between astronomical dawn and sunrise or between sunset and astronomical dusk.
- TWISTEX
- An acronym for Tactical Weather-Instrumented Sampling in/near Tornadoes EXperiment.
- typhoon
- The local name for a tropical cyclone that occurs in the northwestern Pacific Ocean, between 180° and 100°E in the Northern Hemisphere.
U[edit]
- unstable airmass
- updraft
- upper-air chart
- upper-air sounding
- upper-air trough
- upper-level low
- upper-level outflow
- upslope fog
- urban heat island
- US Standard Atmosphere
- University Corporation for Atmospheric Research (UCAR)
- UTC
V[edit]
- valley breeze
- valley exit jet
- vertical draft
- See updraft.
- vertically integrated liquid (VIL)
- vertical wind shear
- virga
- virtual temperature
- visibility
- visual flight rules (VFR)
- A set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going, as opposed to instrument flight rules, under which operation of the aircraft primarily occurs through referencing the onboard instruments rather than through visual reference to the ground and environs.
- Von Kármán constant
- Von Kármán vortex street
- Von Kármán wind turbulence model
- vortex
- A region within a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices are a major component of turbulence and may be observed in many types of meteorological phenomena, including the winds surrounding a tropical cyclone, tornado or dust devil.
- vorticity
W[edit]
- wall cloud
- A large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form.
- warm front
- Warning Decision Training Branch (WDTB)
- water vapor
- Water in its gaseous state. Water vapor is ubiquitous in the atmosphere, being continuously generated by evaporation and removed by condensation, and plays a major role in numerous meteorological processes.
- waterspout
- weak echo region (WER)
- weather
- The state of the atmosphere at a given time and location. Weather is driven by a diverse set of naturally occurring phenomena, especially air pressure, temperature, and moisture differences between one place and another, most of which occur in the troposphere.
- weather balloon
- weather bomb
- weather forecasting
- The application of science and technology to predict the conditions of the atmosphere at a given time and location. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere at a given place and then using meteorology to project how the atmosphere will change. Forecasting is important to a wide variety of human activities, including business, agriculture, transportation, recreation and general health and safety, because it can be used to protect life and property.
- weather front
- See front.
- weather map
- A map which displays various meteorological features across a particular area for a particular point or range of time. Weather maps often use symbols such as station models to conveniently present complicated meteorological data. They are used for both research and weather forecasting purposes.
- weather modification
- Weather Prediction Center (WPC)
- Weather Surveillance Radar (WSR)
- 1. In the United States, WSR-1, WSR-57, WSR-74, and WSR-88D.
- 2. In Canada, the Canadian weather radar network (WKR and CWMN).
- weather reconnaissance
- weather satellite
- weather spotting
- The act of observing weather, often on the ground, for the purpose of reporting to a larger group or organization, such as the U.S. National Weather Service.
- weather station
- weather vane
- Weatherwise
- A photographically adorned general interest weather magazine that frequently publishes articles on tornadoes and other severe weather.
- wet-bulb temperature
- wet-bulb globe temperature
- wet season
- whirlwind
- wildfire
- willy-willy
- See dust devil.
- wind
- The bulk movement of air within the Earth's atmosphere. Wind occurs on a wide range of scales, from very strong thunderstorm flows lasting tens of minutes to milder local breezes lasting a few hours to global atmospheric circulations caused by the differential heating of the Equator and the poles and the Earth's rotation. Winds are often referred to by their strength and direction; the many types of wind are classified according to their spatial scale, their speed, the types of forces that cause them, the regions in which they occur, and their effects.
- wind chill
- wind direction
- wind gradient
- wind gust
- wind profiler
- wind shear
- Any 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 horizontal.
- wind speed
- windstorm
- windsock
- winter
- winter storm
- 1. Any storm which occurs during the local winter.
- 2. Any meteorological event in which varieties of precipitation which can only occur at low temperatures are formed, such as snow, sleet, or freezing rain. Such events are not necessarily restricted to the winter season but may occur in late autumn or early spring, or very rarely in the summer, as well.
- winter waterspout
- World Meteorological Organization (WMO)