• Weather Glossary (E)

    From Daryl Stout@57:57/10 to All on Mon Oct 19 00:07:09 2020
    This weather glossary contains information on more than 2000 terms,
    phrases and abbreviations used by the National Weather Service (NWS)...
    the government agency who makes weather forecasts, and issues weather advisories, watches, and warnings, for the United States, and its
    territories.

    Many of these terms and abbreviations are used by NWS forecasters to communicate between each other and have been in use for many years and
    before many NWS products were directly available to the public. It is the purpose of this glossary to aid you in better understanding NWS products.

    ***

    E
    East

    E REGION
    In 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 Station
    In hydrologic terms, a report to be completed every 5 years providing a complete history of a river station and all gages that have been used for public forecasts since the establishment of the station.

    E-19a, Abridged Report on River Gage Sta
    In 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 intervening five year period. An E-19a is to be completed anytime a
    significant change occurs at a forecast point. An E-19a is also used to
    take the place of an E-19 in documenting any gage history, or information
    of any non-forecast point (i.e; data point).

    E-3, Flood Stage Report
    In hydrologic terms, a 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 crest dates and stages. Discussion of the
    flood event must also be included in the E-5, Monthly Report of River and
    Flood conditions. An E-3 report is sent to Regional Headquarters, the appropriate RFC, as well as the Office of Hydrology (OH).

    E-5, Monthly Report of River and Flood c
    In hydrologic terms, a monthly narrative report covering flooding which occurred over the past month. Flood stage, flood crest and dates in which flooding occurred is covered within this report for each data point which
    was in flood. If the flooding involved a forecast point, an E-3 must be
    filled out as well. If no flooding has occurred within the past month, a climatic summary of the past month can be included as well as other
    interesting non-flood events, such as water supply, ice jams and the
    occurrence of drought. An E-5 report is sent to Regional Headquarters,
    the appropriate RFC, as well as the Office of Hydrology (OH).

    E-7, Flood Damage Report
    In hydrologic terms, a report to be completed anytime there is reported
    flood damage or loss of life as a direct result of flooding. An E-7 report
    is sent to Regional Headquarters, as well as the Office of Hydrology (OH).

    Easterlies
    Any winds with components from the east.

    Ebb Current
    The movement of a tidal current away form the coast or down an estuary.

    EBND
    Eastbound

    EBS
    Emergency Broadcast System

    Eccentricity
    A dimensionless quantity describing the elliptical shape of a planet's
    orbit.

    Echo
    Energy back scattered from a target (precipitation, clouds, etc.) and
    received by and displayed on a radar screen.

    Echo Tops
    The 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 dBZ can be detected.

    ECMF
    European Center for Meteorology Forecast model.

    ECMWF
    European Center for Medium-Range Weather Forecasts. Operational
    references in forecast discussions typically refer to the ECMWF's
    medium-range numerical forecast model, which runs out to 10 days.

    Eddy
    Swirling currents of air at variance with the main current.

    EDT
    Eastern Daylight Time

    EFCT
    Effect

    Effective Porosity
    In hydrologic terms, the ratio, usually expressed as a percentage, of
    the volume of water or other liquid which a given saturated volume of
    rock or soil will yield under any specified hydraulic condition, to the
    given volume of soil or rock.

    Effective Precipitation

    1) That part of the precipitation that produces runoff.

    2) A weighted average of current and antecedent precipitation that is "effective" in correlating with runoff.

    3) That part of the precipitation falling on an irrigated area that is effective in meeting the consumptive use requirements.

    Effective Terrestrial Radiation
    The difference between upwelling infrared or terrestrial radiation
    emitted from the earth and the downwelling infrared radiation from the atmosphere.

    Effective Topography
    The 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 actual topography.

    Effluent Seepage
    In hydrologic terms, diffuse discharge of ground water to the ground
    surface.

    Effluent Stream
    In hydrologic terms, any 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 Nio
    A 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 region; a major El Nio event generally occurs every
    3 to 7 years and is associated with changes in the weather patterns
    worldwide.

    Element
    One of the basic conditions of the atmosphere discussed in this FMH
    (wind, visibility, runway visual range, weather, obscurations, sky
    condition, temperature and dewpoint, and pressure). See parameter.

    ELEV
    Elevation

    Elevated Convection
    Convection occurring within an elevated layer, i.e., a layer in which
    the lowest portion is based above the earth's surface. Elevated
    convection often occurs when air near the ground is relatively cool
    and stable, e.g., during periods of isentropic lift, when an unstable
    layer of air is present aloft.

    In cases of elevated convection, stability indices based on near-surface measurements (such as the lifted index) typically will underestimate the
    amount of instability present. Severe weather is possible from elevated convection, but is less likely than it is with surface-based convection.

    ELSW
    Elsewhere

    ELY
    Easterly

    Embankment
    In hydrologic terms, fill material, usually earth or rock, placed with
    sloping sides and usually with length greater than height. All dams are
    types of embankments.

    EMBDD
    Embedded

    EMC
    Environmental Modeling Center

    Emergency Action Plan
    In hydrologic terms, a predetermined plan of action to be taken to reduce
    the potential for property damage and loss of life in an area affected by
    a dam break or excessive spillway.

    Emergency Services
    In hydrologic terms, services provided in order to minimize the impact of
    a flood that is already happening. These measures are the responsibility
    of city, or county emergency management staff and the owners or operators
    of major, or critical facilities. Some examples of emergency services are
    flood warning and evacuation, flood response, and post flood activities.

    Emerging Flux Region (EFR)
    In solar-terrestrial terms, an area on the sun where new magnetic flux is erupting.

    Emissivity
    The ability of a surface to emit radiant energy compared to that of a
    black body at the same temperature and with the same area.

    EML
    Elevated Mixed Layer

    ENDG
    Ending

    Energy Dissipator
    In hydrologic terms, a structure which slows fast-moving spillway flows in order to prevent erosion of the stream channel.

    Energy Helicity Index
    An index that incorporates vertical shear and instability, designed for
    the purpose of forecasting supercell thunderstorms.

    Engineer's Level
    A telescope which is attached to a spirit-tube level, all revolving around
    a vertical axis and is mounted on a tripod. An Engineer's Level is used
    for determining the difference in elevation between two points. The
    telescope on the level has a vertical cross hair and a horizontal cross
    hair. Once the instrument is leveled, the sighting through the horizontal
    cross hair represents a horizontal plane of equal elevation.

    Enhanced V
    A pattern seen on satellite infrared photographs of thunderstorms, in
    which a thunderstorm anvil exhibits a V-shaped region of colder cloud
    tops extending downwind from the thunderstorm core. The enhanced V
    indicates a very strong updraft, and therefore a higher potential for
    severe weather. Enhanced V should not be confused with V notch, which is
    a radar signature.

    Enhanced Wording

    1. An option used by the SPC in tornado and severe thunderstorm watches
    when the potential for strong/violent tornadoes, or unusually widespread damaging straight-line winds, is high. The text that accompanies a watch
    of this type will include the line "THIS IS A PARTICULARLY DANGEROUS SITUATION."

    2. Strong wording or emphasis used in a zone forecast issued by a National Weather Service Forecast Office highlighting a potential condition
    (e.g., "some thunderstorms may be severe").

    ENHNCD
    Enhanced

    ENSEMBLE
    A collection of numerical model results that show slightly different
    possible outcomes.

    Ensemble Forecast
    Multiple predictions from an ensemble of slightly different initial
    conditions and/or various versions of models. The objectives are to
    improve the accuracy of the forecast through averaging the various
    forecasts, which eliminates non-predictable components, and to provide
    reliable information on forecast uncertainties from the diversity amongst ensemble members. Forecasters use this tool to measure the likelihood of
    a forecast.

    Ensemble Hydrologic Forecasting
    In hydrologic terms, a process whereby a continuous hydrologic model is successively executed several times for the same forecast period by use
    of varied data input scenarios, or a perturbation of a key variable state
    for each model run. A common method employed to obtain a varied data input scenario is to use the historical meteorological record, with the
    assumption that several years of observed data covering the time period beginning on the current date and extending through the forecast period comprises a reasonable estimate of the possible range of future
    conditions.

    Ensembles
    Reference to a set of computer models run under the concept of Ensemble Forecasting: multiple predictions from an ensemble of models with
    slightly different initial conditions used as input and/or slightly
    different versions of models. The objectives are to improve the accuracy
    of the forecast through averaging the various forecasts, which eliminates non-predictable components, and to provide reliable information on
    forecast uncertainties from the diversity amongst ensemble members.
    Forecasters use this tool to measure the likelihood of a forecast.

    ENSO
    Abbreviation for El Nio-Southern Oscillation, a reference to the state
    of the Southern Oscillation.

    ENSO Diagnostic Discussion
    The CPC issues the ENSO Diagnostic Discussion around the middle of the
    month. The discussion addresses the current oceanic and atmospheric
    conditions in the Pacific and the seasonal climate outlook for the
    following one to three seasons.

    ENTR
    Entire

    Entrainment Zone
    A shallow region at the top of a convective boundary layer where fluid
    is entrained into the growing boundary layer from the overlying fluid by
    the collapse of rising convective plumes or bubbles.

    Entrance Region
    The region upstream from a wind speed maximum in a jet stream (jet max),
    in which air is approaching (entering) the region of maximum winds, and therefore is accelerating. This acceleration results in a vertical
    circulation that creates divergence in the upper-level winds in the
    right half of the entrance region (as would be viewed looking along the direction of flow).

    This divergence results in upward motion of air in the right rear quadrant
    (or right entrance region) of the jet max. Severe weather potential
    sometimes increases in this area as a result. See also exit region, left
    exit region.

    Entropy
    The amount of energy that is not available for work during a certain
    process.

    Environment Canada
    The Canadian federal government department responsible for issuing
    weather forecasts and weather warnings in Canada.

    Environmental Lapse Rate
    The rate of decrease of air temperature with height, usually measured
    with a radiosonde.

    Environmental Temperature Sounding
    An instantaneous or near-instantaneous sounding of temperature as a
    function of height. This sounding or vertical profile is usually
    obtained by a balloon-borne instrument, but can also be measured using
    remote sensing equipment.

    EPA
    Environmental Protection Agency

    EPCTG
    Expecting

    EPV
    Equivalent Potential Vorticity

    Equi-Potential Line
    In hydrologic terms, a line, in a field of flow, such that the total head
    is the same for all points on the line, and therefore the direction of
    flow is perpendicular to the line at all points.

    Equilibrium Drawdown
    In hydrologic terms, the ultimate, constant drawdown for a steady rate of pumped discharge.

    Equilibrium Level
    (EL) - On a sounding, the level above the level of free convection (LFC)
    at which the temperature of a rising air parcel again equals the
    temperature of the environment. The height of the EL is the height at
    which thunderstorm updrafts no longer accelerate upward. Thus, to a
    close approximation, it represents the height of expected (or ongoing) thunderstorm tops.

    Equilibrium Surface Discharge
    In hydrologic terms, the steady rate of surface discharge which results
    from a long-continued, steady rate of net rainfall, with discharge rate
    equal to net rainfall rate.

    Equilibrium Time
    In hydrologic terms, the time when flow conditions become substantially
    equal to those corresponding to equilibrium discharge or equilibrium
    drawdown.

    Equinox
    The time when the sun crosses the earth's equator, making night and day
    of approximately equal length all over the earth and occurring about
    March 21 (the spring or vernal equinox) and September 22 (autumnal
    equinox). These are reversed in the southern hemisphere.

    Equivalent Potential Temperature
    The equivalent potential temperature is the temperature a parcel at a
    specific pressure level and temperature would have if it were raised to
    0 mb, condensing all moisture from the parcel, and then lowered to 1000
    mb.

    ERLY
    Early

    ERN
    Eastern

    Erosion
    In hydrologic terms, wearing away of the lands by running water,
    glaciers, winds, and waves, can be subdivided into three process:
    Corrasion, Corrosion, and Transportation. Weathering, although sometimes included here, is a distant process which does not imply removal of any material.

    Eruptive
    In solar-terrestrial terms, solar activity levels with at least one
    radio event (10 cm) and several chromospheric events per day (Class C
    Flares).

    Eruptive Prominence on Limb (EPL)
    In solar-terrestrial terms, a solar prominence that becomes activated
    and is seen to ascend from the sun.

    ESP
    Extended Streamflow Prediction

    EST
    Eastern Standard Time

    Estuary
    In hydrologic terms, the thin zone along a coastline where freshwater
    systems and rivers meet and mix with a salty ocean (such as a bay, mouth
    of a river, salt marsh, lagoon).

    Esturine waters
    In hydrologic terms, deepwater tidal habitats and tidal wetlands that are usually enclosed by land but have access to the ocean and are at least occasionally diluted by freshwater runoff from the land (such as bays,
    mouths of rivers, salt marshes, lagoons).

    Esturine Zone
    In hydrologic terms, the area near the coastline that consists of
    esturaries and coastal saltwater wetlands.

    ETA

    1. The Eta Model, now referred to as North Amercian Meso (NAM) an
    84-hour numerical model of the atmosphere run four times daily by NCEP.
    This is one of the main forecast models used for short-term weather
    prediction in the United States.

    2. Estimated Time of Arrival

    Eta Model

    Now referred to as North Amercian Meso (NAM) is one of the operational numerical forecast models run at NCEP. The Eta is run four times daily,
    with forecast output out to 84 hours.

    Evaporation
    The process of a liquid changing into a vapor or gas, usually water in meteorology.

    Evaporation Pan
    In hydrologic terms, a pan used to hold water during observations for
    the determination of the quantity of evaporation at a given location.
    Such pans are of varying sizes and shapes, the most commonly used being circular or square.

    Evaporation Rate
    In hydrologic terms, the quantity of water, expressed in terms of depth
    of liquid water, which is evaporated from a given surface per unit of
    time. It is usually expressed in inches depth, per day, month, or year.

    Evaporation-mixing Fog
    Fog that forms when the evaporation of water raises the dew point of the adjacent air.

    Evaporimeter
    In hydrologic terms, an instrument which measures the evaporation rate
    of water into the atmosphere.

    Evapotranspiration
    Combination of evaporation from free water surfaces and transpiration
    of water from plant surfaces to the atmosphere.

    EVE
    Evening

    EWD
    Eastward

    EWW
    Extreme Wind Warning (EWW) inform the public of the need to take
    immediate shelter in an interior portion of a well-built structure due
    to the onset of extreme tropical cyclone winds. An EWW for extreme
    tropical cyclone winds should be issued when both of the following
    criteria are met:

    a. Tropical cyclone is a category 3 or greater on the Saffir Simpson
    hurricane scale as designated by NHC, CPHC or JTWC.

    b. Sustained tropical cyclone surface winds of 100 knots (115 mph) or
    greater are occurring or are expected to occur in a WFO's county
    warning area within one hour.

    Excess Rain
    In hydrologic terms, effective rainfall in excess of infiltration
    capacity.

    Excessive Heat
    Excessive heat occurs from a combination of high temperatures
    (significantly above normal) and high humidities. At certain levels,
    the human body cannot maintain proper internal temperatures and may
    experience heat stroke. The "Heat Index" is a measure of the effect of
    the combined elements on the body.

    Excessive Heat Outlook
    This CPC product, a combination of temperature and humidity over a
    certain number of days, is designed to provide an indication of areas
    of the country where people and animals may need to take precautions
    against the heat during May to November.

    Excessive Heat Warning
    Issued within 12 hours of the onset of the following criteria: heat
    index of at least 105F for more than 3 hours per day for 2
    consecutive days, or heat index more than 115F for any period of
    time.

    Excessive Heat Watch
    Issued by the National Weather Service when heat indices in excess of
    105F (41C) during the day combined with nighttime low temperatures of
    80F (27C) or higher are forecast to occur for two consecutive days.

    EXCLD
    Exclude

    Exclusive Flood Control Storage Capacity
    In hydrologic terms, the space in a reservoir reserved for the sole
    purpose of regulating flood inflows to abate flood damage.

    Exit Region
    The region downstream from a wind speed maximum in a jet stream
    (jet max), in which air is moving away from the region of maximum winds,
    and therefore is decelerating. This deceleration results in divergence
    in the upper-level winds in the left half of the exit region (as would
    be viewed looking along the direction of flow).

    This divergence results in upward motion of air in the left front
    quadrant (or left exit region) of the jet max. Severe weather potential sometimes increases in this area as a result. See also entrance region,
    right entrance region.

    Exosphere
    The upper most layer of the earth's atmosphere; the only layer where atmospheric gases can escape into outer space.

    Experimental Product
    An experimental product is in the final stages of testing and evaluation.
    If the product proves accurate and valuable to users then the next step
    is to make it an operational product.

    Explosive Deepening
    A decrease in the minimum sea-level pressure of a tropical cyclone of
    2.5 mb/hr for at least 12 hours or 5 mb/hr for at least six hours.

    EXTD
    Extend/Extended

    Extended Forecast Discussion
    This discussion is issued once a day around 2 PM EST (3 PM EDT) and is primarily intended to provide insight into guidance forecasts for the
    3 to 5 day forecast period. The geographic focus of this discussion is
    on the United States (including Alaska and Hawaii). Although portions
    of this narrative will parallel the Hemispheric Map Discussion, a much
    greater effort is made to routinely relate the model forecasts and
    necessary modifications to weather forecasts, mainly in terms of
    temperature and precipitation.

    Extraterrestrial Radiation
    The theoretically-calculated radiation flux from the sun at the top of
    the atmosphere, before losses by atmospheric absorption.

    Extratropical
    A term used in advisories and tropical summaries to indicate that a
    cyclone has lost its "tropical" characteristics. The term implies both
    poleward displacement of the cyclone and the conversion of the
    cyclone's primary energy source from the release of latent heat of
    condensation to baroclinic (the temperature contrast between warm and
    cold air masses) processes. It is important to note that cyclones can
    become extratropical and still retain winds of hurricane or tropical
    storm force.

    Extratropical Cyclone
    A cyclone in the middle and high latitudes often being 2000 kilometers
    in diameter and usually containing a cold front that extends toward the
    equator for hundreds of kilometers.

    Extratropical Low
    A low pressure center which refers to a migratory frontal cyclone of
    middle and higher latitudes. Tropical cyclones occasionally evolve into extratropical lows losing tropical characteristics and become associated
    with frontal discontinuity.

    Extreme Ultraviolet (EUV)
    A portion of the electromagnetic spectrum from approximately 100 to 1000 angstroms.

    Extreme Wind Warning
    Extreme Wind Warning (EWW) inform the public of the need to take immediate shelter in an interior portion of a well-built structure due to the onset
    of extreme tropical cyclone winds. An EWW for extreme tropical cyclone
    winds should be issued when both of the following criteria are met:

    a. Tropical cyclone is a category 3 or greater on the Saffir Simpson
    hurricane scale as designated by NHC, CPHC or JTWC.

    b. Sustained tropical cyclone surface winds of 100 knots (115 mph) or
    greater are occurring or are expected to occur in a WFO's county warning
    area within one hour.

    Extremely Low Frequency (ELF)
    That portion of the radio frequency spectrum from 30 to 3000 hertz.

    EXTRM
    Extreme

    EXTSV
    Extensive

    Eye
    The relatively calm center in a hurricane that is more than one half
    surrounded by wall cloud. The winds are light, the skies are partly
    cloudy or even clear (the skies are usually free of rain) and radar
    depicts it as an echo-free area within the eye wall.

    Eye Wall
    It is an organized band of cumuliform clouds that immediately surrounds
    the center (eye) of a hurricane. The fiercest winds and most intense
    rainfall typically occur near the eye wall. VIP levels 3 or greater are typical. Eye wall and wall cloud are used synonymously, but it should
    not be confused with a wall cloud of thunderstorm.
    --- SBBSecho 3.11-Win32
    * Origin: The Thunderbolt BBS - tbolt.synchro.net (57:57/10)