Condensation FunnelA funnel-shaped cloud associated with rotation and consisting of condensed water droplets (as opposed to smoke, dust, debris, etc.).
Conditionally Unstable AirAn atmospheric condition that exists when the environmental lapse rate is less than the dry adiabatic lapse rate but greater than the moist adiabatic…
ConductionThe transfer of heat through a material by the transfer of kinetic energy from particle to particle; the flow of heat between two materials of different…
Cone of DepressionA depression in the water table that develops around a pumped well.
Cone of InfluenceThe depression, roughly conical in shape, produced in a water table, or other piezometric surface, by the extraction of water from a well at a given rate.
Conference of the PartiesThe supreme body of the United Nations Framework Convention on Climate Change (UNFCCC).
Confined Ground WaterGround water held under an aquiclude or an aquifuge called artesian if the pressure is positive.
ConfluenceThe place where two streams meet, or the stream formed from two joining streams.
Congestus(or Cumulus Congestus) - same as towering cumulus.
Congressional Organic Act of 1890The act that assigned the responsibility of river and floor forecasting for the benefit of the general welfare of the Nation's people and economy to the…
ConiferA plant commonly having needlelike, persistent leaves and a woody cone for a fruit.
Coniferous treesCone-bearing trees, mostly evergreens, that have needle-shaped or scale-like leaves. They produce wood known commercially as softwood. See deciduous trees.
ConingWith regards to wildfires, pattern of plume dispersion in a neutral atmosphere, in which the plume attains the form of a cone with its vertex at the top…
Conjugate PointsTwo points on the earth's surface, at opposite ends of a geomagnetic field line
Conservation StorageStorage of water for later release for usual purposes such as municipal water supply, power, or irrigation in contrast with storage capacity used for…
Consolidated Ice CoverIce cover formed by the packing and freezing together of floes, brash ice and other forms of floating ice.
Constant Pressure ChartAlternate term for Isobaric Chart; a weather map representing conditions on a surface of equal atmospheric pressure.
ContentsThe volume of water in a reservoir. Unless otherwise indicated reservoir content is computed on the basis of a level pool and does not include bank…
Continental Air MassA dry air mass originating over a large land area. Contrast with tropical air mass.
Continental ShelfThe zone bordering a continent and extending to a depth, usually around 100 FM, from which there is a steep descent toward greater depth.
Continuum Storm (CTM)In solar-terrestrial terms, general term for solar noise lasting for hours and sometimes days.
contrail (condensation trail)A cloudlike streamer frequently seen forming behind aircraft flying in clear, cold, humid air.
Control PointsHorizontal and Vertical: Small monuments securely embedded in the surface of the dam. Any movement of the monument indicates a movement in the dam itself.
ConvectionThe movement of matter due to changes in temperature and density. Warm material rises because it is less dense (lighter) and cool material sinks because…
Convection cloudConvection cloud Cumuliform cloud which forms in the atmosphere as a result of convection. Such clouds are also called clouds of vertical development.
Convective Boundary LayerThe unstable boundary layer that forms at the surface and grows upward through the day as the ground is heated by the sun and convective currents transfer…
Convective CloudsThe vertically developed family of clouds are cumulus and cumulonimbus. The height of their bases range from as low as 1,000 feet to a bit more than…
Convective Condensation Level(abbrev. CCL)- The level in the atmosphere to which an air parcel, if heated from below, will rise dry adiabatically, without becoming colder than its…
convective condensation level (CCL)(CCL)The level above the surface marking the base of a cumuliform cloud that is forming due to surface heating and rising thermals.
Convective Inhibition(CIN or B-) - A numerical measure of the strength of "capping," typically used to assess thunderstorm potential.
Convective Outlook(sometimes called AC) - A forecast containing the area(s) of expected thunderstorm occurrence and expected severity over the contiguous United States…
Convective OverdevelopmentConvection that covers the sky with clouds, thereby cutting off the sunshine that produces convection.
Convective TemperatureThe approximate temperature that the air near the ground must warm to in order for surface-based convection to develop, based on analysis of a sounding.
ConvergenceIntegration of computing, communications and broadcasting systems.
Conveyance LossThe loss of water from a conduit due to leakage, seepage, evaporation, or evapo-transpiration.
Cooling Degree Days(Abbrev. CDD) - A form of Degree Day used to estimate energy requirements for air conditioning or refrigeration.
cooperating programA program or agency supporting a specific ARM effort, such as a field campaign, wherein ARM provides the resources.
Cooperative ObserverAn individual (or institution) who takes precipitation and temperature observations-and in some cases other observations such as river stage, soil…
Coordinated Universal Time (UTC)By international agreement, the local time at the prime meridian, which passes through Greenwich, England.
Core Punch[Slang], a penetration by a vehicle into the heavy precipitation core of a thunderstorm. Core punching is not a recommended procedure for storm spotting.
Coriolis ForceA fictitious force used to account for the apparent deflection of a body in motion with respect to the earth, as seen by an observer on the earth.
Corner EffectsA small-scale convergence effect that can be quite severe. It occurs around steep islands and headlands.
CoronaThe outermost layer of the Sun’s outer atmosphere. This halo of ions extends millions of miles into space and consists of a gas that is much thinner…
Coronal HoleAn area of the corona that appears dark when viewed in ultraviolet light. They are usually located around the poles of the Sun, but can occur at other…
Coronal Rain(Abbrev. CRN) In solar-terrestrial terms, material condensing in the corona and appearing to rain down into the chromosphere as observed at the solar limb…
Coronal TransientsIn solar-terrestrial terms, a general term for short-time-scale changes in the corona, but principally used to describe outward-moving plasma clouds.
Corrective Action Report (CAR)(CAR)Used to identify and document problems with ARM systems, physical infrastructure, or instruments.
Correlated ShearAn output of the mesocyclone detection algorithm indicating a 3-dimensional shear region (i.e. vertically correlated) that is not symmetrical.
CorrelationIn investment terms, correlation is the extent to which the values of different types of investments move in tandem with one another in response to…
Cosmic RayHigh energy charged particles traveling through interstellar space at nearly the velocity of light. Most are produced in supernova explosions.
County Warning and Forecast AreaThe group of counties for which a National Weather Service Forecast Office is responsible for issuing warnings and weather forecasts.
County Warning AreaThe group of counties for which a National Weather Service Forecast Office is responsible for issuing warnings.
Coupled Atmosphere-Ocean ModelSame as Coupled Model; in the context of climate modeling this usually refers to a numerical model which simulates both atmospheric and oceanic motions…
Coupled ModelIn the context of climate modeling this usually refers to a numerical model which simulates both atmospheric and oceanic motions and temperatures and…
CoupletAdjacent maxima of radial velocities of opposite signs.
CreekA small stream of water which serves as the natural drainage course for a drainage basin of nominal, or small size.
Crepuscular RaysThe alternating bands of light and dark (rays and shadows) seen at the earth's surface when the sun shines through clouds.
CrestThe top surface of the dam. A roadway may be constructed across the crest to permit vehicular traffic or facilitate operation, maintenance, and…
Crest GageA gage used to obtain a record of flood crests at sites where recording gages are installed.
Crest WidthThe width or thickness of a dam at the level of the crest of the dam. In general, the term "thickness" is used for gravity and arch dams and "width" is…
Criteria pollutantA pollutant determined to be hazardous to human health and regulated under EPA's National Ambient Air Quality Standards.
Critical DepthThe depth of flow when the Froude number equals one. The depth of flow at which the discharge is maximum for a given specific energy, or the depth at…
Critical FlowWhen the Froude number is equal to one, the flow is critical and surface waves remain stationary in the flow. Flow at critical depth.
Critical Rainfall Probability(Abbrev. CRP) - In hydrologic terms, the Probability that the actual precipitation during a rainfall event has exceeded or will exceed the flash flood…
CRNCoronal Rain - In solar-terrestrial terms, material condensing in the corona and appearing to rain down into the chromosphere as observed at the solar…
CrochetIn solar-terrestrial terms, a sudden deviation in the sunlit geomagnetic field (H component; see geomagnetic elements) associated with large solar flare…
Crop Moisture IndexIn 1968, Palmer developed the index to assess short-term crop water conditions and needs across major crop-producing regions.
Crop residueOrganic residue remaining after the harvesting and processing of a crop.
Crop rotationA pattern of changing the crops grown in a specific field from year to year in order to control pests and maintain soil fertility.
Cross-Valley Wind SystemA thermally driven wind that blows during daytime across the axis of a valley toward the heated sidewall.
Crown FireA fire where flames travel from tree to tree at the level of the tree's crown or top.
CrowningMovement of a fire from the understory into the crown of a forest canopy.
CRPAbbreviation for catabolite regulator protein. See: catabolite activator protein.
CRSConsole Replacement System for NOAA Weather Radio
Crude oilA mixture of hydrocarbons that exist in liquid phase in underground reservoirs and remain liquid at atmospheric pressure after passing through surface…
CryologyThe science of the physical aspects of snow, ice, hail, and sleet and other forms of water produced by temperatures below Zero degrees Celsius.
CryosphereOne of the interrelated components of the Earth's system, the cryosphere is frozen water in the form of snow, permanently frozen ground (permafrost)…
crystal habitThe size and shape of the crystals in a crystalline solid. Also known as habit.
CUCumulus clouds - Detached clouds, generally dense and with sharp outlines, showing vertical development in the form of domes, mounds, or towers.
Cubic Feet Per SecondA unit expressing rates of discharge. One cubic foot per second is equal to the discharge through a rectangular cross section, 1 foot wide by 1 foot deep…
CumuliformDescriptive of all clouds with vertical development in the form of rising mounds, domes, or towers
Cumuliform AnvilA thunderstorm anvil with visual characteristics resembling cumulus-type clouds (rather than the more typical fibrous appearance associated with cirrus).
CumulonimbusA cloud belonging to a class indicative of thunderstorm conditions characterized by large, dense towers that often reach altitudes of 30,000 feet (9000…
Cumulus(Abbrev. CU) - detached clouds, generally dense and with sharp outlines, showing vertical development in the form of domes, mounds, or towers.
Cumulus BuildupsClouds which develop vertically due to unstable air. Characterized by their cauliflower-like or tower-like appearance of moderately large size
Cumulus CongestusA large, towering cumulus cloud with great vertical development, usually with a cauliflower-like appearance, but lacking the characteristic anvil of a…
cup anemometerAn instrument used to monitor wind speed. Wind rotation of cups generates and electric current calibrated in wind speed.
CurrentA horizontal movement of water. Currents may be classified as tidal and nontidal.