DWNDFTDowndraft - A small-scale column of air that rapidly sinks toward the ground, usually accompanied by precipitation as in a shower or thunderstorm.
DWPTDew Point - A measure of atmospheric moisture. It is the temperature to which air must be cooled in order to reach saturation (assuming air pressure and…
Dynamic IcePressure due to a moving ice cover or drifting ice.
Dynamic LiftingThe forced uplifting of air from various atmospheric processes, such as weather fronts, and cyclones.
Dynamic Wave Routing Model (DWOPER)(DWOPER)A computerized hydraulic routing program whose algorithms incorporate the complete one-dimensional equations of unsteady flow originally developed by…
E REGIONIn solar-terrestrial terms, a daytime layer of the earth's ionosphere roughly between the altitudes of 85 and 140 km.
E-19, Report on River Gage StationA report to be completed every 5 - 10 years providing a complete history of a river station and all gages that have been used for public forecasts since…
E-19a, Abridged Report on River Gage StaIn hydrologic terms, an abridged version of an E-19, an E-19a updates the E-19 as additional information, or changes occur at the station during the…
E-3, Flood Stage ReportA form that a Service Hydrologist/ Hydrology Focal Point completes to document the dates in which forecast points are above flood stage, as well as the…
E-7, Flood Damage ReportA report to be completed anytime there is reported flood damage or loss of life as a direct result of flooding.
Earth radiationEarth radiation (terrestrial radiation) The total infrared radiation emitted from the Earth's surface; to be carefully distinguished from effective…
EasterliesAny winds with components from the east.
Eastern North Pacific BasinThe portion of the North Pacific Ocean east of 140W. The National Hurricane Center in Miami, Florida is responsible for tracking tropical cyclones in this…
Ebb CurrentThe movement of a tidal current away form the coast or down an estuary.
EccentricityA dimensionless quantity describing the elliptical shape of a planet's orbit.
EchoEnergy back scattered from a target (precipitation, clouds, etc.) and received by and displayed on a radar screen.
Echo TopsThe height above ground of the center of the radar beam using the tilt, or scan, that contains the highest elevation where reflectivities greater than 18…
ECMFEuropean Center for Meteorology Forecast model.
ECMWFEuropean Center for Medium-Range Weather Forecasts. Operational references in forecast discussions typically refer to the ECMWF's medium-range numerical…
EconomyThe way a country manages its money and resources (such as workers and land) to produce, buy, and sell goods and services.
EcosystemA complex ecological community or environment forming a functioning whole.
EddyCircular current of water moving against the main current. See recirculation zone.
effective emissivityA correction factor, dependent on the radiational characteristics of the earth-atmosphere system, that permits application of black body radiation laws to…
Effective PorosityThe ratio of the volume of a soil or rock mass that can be drained by gravity to the total volume of the mass.
Effective Precipitation1) That part of the precipitation that produces runoff. 2) A weighted average of current and antecedent precipitation that is "effective" in correlating…
Effective Terrestrial RadiationThe difference between upwelling infrared or terrestrial radiation emitted from the earth and the downwelling infrared radiation from the atmosphere
Effective TopographyThe topography as seen by an approaching flow, which may include not only the actual terrain but also cold air masses trapped within or adjacent to the…
Effluent SeepageDiffuse discharge of ground water to the ground surface.
Effluent StreamAny watercourse in which all, or a portion of the water volume came from the Phreatic zone, or zone of saturation by way of groundwater flow, or baseflow.
El NiñoA warming of the ocean current along the coasts of Peru and Ecuador that is generally associated with dramatic changes in the weather patterns of the…
El Ni�A climatic phenomenon occurring irregularly, but generally every 3 to 5 years. El Ni�s often first become evident during the Christmas season…
El Ni� - Southern Oscillation (ENSO)El Ni�, in its original sense, is a warm water current that periodically flows along the coast of Ecuador and Peru, disrupting the local…
ElectronsTiny particle moving around outside the nucleus of an atom. Each electron has one unit of negative charge (-) and almost no mass.
element(EH-leh-ment) A basic part of a whole. In chemistry, refers to a simple substance that cannot be broken down into smaller parts or changed into another…
Emergency Action PlanA predetermined plan of action to be taken to reduce the potential for property damage and loss of lives in an area affected by a dam break or excessive…
Emergency ServicesEvaluation of an emergency medical condition and treatment to keep the condition from getting worse.
Emerging Flux Region (EFR)In solar-terrestrial terms, an area on the sun where new magnetic flux is erupting.
Emission inventoryA list of air pollutants emitted into a community's, state's, nation's, or the Earth's atmosphere in amounts per some unit time (e.g.
EmissionsWaste substances released into the air or water.
Emissions coefficient/factorA unique value for scaling emissions to activity data in terms of a standard rate of emissions per unit of activity (e.g.
Emissions FactorA unique value for scaling emissions to activity data in terms of a standard rate of emissions per unit of activity (e.g.
EmissivityThe ratio of the radiant energy (heat) leaving (being emitted by) a surface to that of a black body at the same temperature and with the same area…
emittanceThe rate at which a black body radiates energy across all wavelengths.
EnergyThe capability of doing work; different forms of energy can be converted to other forms, but the total amount of energy remains the same.
Energy conservationReduction or elimination of unnecessary energy use and waste. See energy-efficiency.
Energy DissipatorA device constructed in a waterway to reduce the kinetic energy of fast flowing water. See stilling basin.
Energy EfficiencyUsing less energy to achieve the same outcome. For example, better insulation would enable a home to stay warm utilizing less energy.
Energy Helicity IndexAn index that incorporates vertical shear and instability, designed for the purpose of forecasting supercell thunderstorms
Energy IntensityThe relative extent that energy is required for a process.
Energy qualityAbility of a form of energy to do useful work. High-temperature heat and the chemical energy in fossil fuels and nuclear fuels are concentrated high…
Engineer's LevelA telescope which is attached to a spirit-tube level, all revolving around a vertical axis and is mounted on a tripod.
Engineering Change Order (ECO)(ECO)An engineering task or project directly resulting from an Engineering Change Request.
Engineering Change Request (ECR)(ECR)A method of formally requesting that a change be made to the infrastructure. This change can be to a particular instrument, data system, data process…
Engineering Work Request (EWR)(EWR)Used to request engineering resources, as soon as possible, when operational, science, or engineering needs require a quick engineering response where no…
Enhanced Greenhouse EffectThe concept that the natural greenhouse effect has been enhanced by anthropogenic emissions of greenhouse gases.
Enhanced oil recoveryRemoval of some of the heavy oil left in an oil well after primary and secondary recovery. See primary oil recovery, secondary oil recovery.
Enhanced VA pattern seen on satellite infrared photographs of thunderstorms, in which a thunderstorm anvil exhibits a V-shaped region of colder cloud tops extending…
Enhanced Wording1. An option used by the SPC in tornado and severe thunderstorm watches when the potential for strong/violent tornadoes, or unusually widespread damaging…
ENSEMBLEA collection of numerical model results that show slightly different possible outcomes.
Ensemble ForecastMultiple predictions from an ensemble of slightly different initial conditions and/or various versions of models.
Ensemble Hydrologic ForecastingA process whereby a continuous hydrologic model is successively executed several times for the same forecast period by use of varied data input scenarios…
EnsemblesReference to a set of computer models run under the concept of Ensemble Forecasting: multiple predictions from an ensemble of models with slightly…
ENSOAbbreviation for El Niño-Southern Oscillation, a reference to the state of the Southern Oscillation.
ENSO Diagnostic DiscussionThe CPC issues the ENSO Diagnostic Discussion around the middle of the month. The discussion addresses the current oceanic and atmospheric conditions in…
Enteric fermentationA digestive process by which carbohydrates are broken down by microorganisms into simple molecules for absorption into the bloodstream of an animal.