Sea BreezeA thermally produced wind blowing during the day from a cool ocean surface onto the adjoining warm land, caused by the difference in the rates of heating…
Sea Breeze Convergence ZoneThe zone at the leading edge of a sea breeze where winds converge. The incoming air rises in this zone, often producing convective clouds.
Sea Breeze FrontThe leading edge of a sea breeze, whose passage is often accompanied by showers, a wind shift, or a sudden drop in temperature.
Sea FogCommon advection fog caused by transport of moist air over a cold body of water.
Sea IceAny form of ice found at sea which has originated from the freezing of sea water (sea ice does NOT include superstructure icing).
Sea Level PressureThe sea level pressure is the atmospheric pressure at sea level at a given location.
Sea smokeSea smoke (arctic sea smoke) Evaporation fog or steam fog which is formed when water vapor is added to air which is much colder than the vapor's source…
Sea surface temperatureSea surface temperature Temperature of the water film at the sea surface.
Sea Surface TemperaturesThe term refers to the mean temperature of the ocean in the upper few meters.
Second-Day FeetThe volume of water represented by a flow of one cubic foot per second for 24 hours; equal to 84,000 cubic feet.
Secondary Ambient Air Quality StandardsAir quality standards designed to protect human welfare, including the effects on vegetation and fauna, visibility and structures.
Secondary oil recoveryInjection of water into an oil well after primary oil recovery to force out some of the remaining thicker crude oil.
Secondary PollutantPollutants generated by chemical reactions occurring within the atmosphere. Compare primary pollutant.
SectorA sector is a segment of the economy that shares distinctive characteristics, such as telecommunications or energy.
Sector BoundaryIn solar-terrestrial terms, in the solar wind, the area of demarcation between sectors, which are large-scale features distinguished by the predominant…
Sector VisibilityThe visibility in a specific direction that represents at least a 45º arc of a horizontal circle.
Sectorized Hybrid ScanA single reflectivity scan composed of data from the lowest four elevation scans. Close to the radar, higher tilts are used to reduce clutter.
SecuriteA headline within National Weather Service high seas forecasts transmitted via the GMDSS to indicate that no hurricane or hurricane force winds are…
SedimentAny finely divided organic and/or mineral matter deposited by air or water in nonturbulent areas.
Semipermanent anticycloneSemipermanent anticyclone (high) High pressure area largely predominate during a major portion of the year where an anticyclone appears on the mean…
Sensible HeatThe heat absorbed or released when a substance undergoes a change in temperature.
Sensible Heat FluxThe flux of heat from the earth's surface to the atmosphere that is not associated with phase changes of water; a component of the surface energy budget.
Separation EddyAn eddy that forms near the ground on the windward or leeward side of a bluff object or steeply rising hillside; streamlines above this eddy go over the…
Septic tankUnderground tank for treatment of wastewater from a home in rural and suburban areas.
Serial DerechoType of derecho that consists of an extensive squall line which is oriented such that the angle between the mean wind direction and the squall line axis…
Servo LoopIn radar meteorology, a generic description of hardware needed to remotely control the motion of the antenna dish.
SetThree of a kind when you have two of the rank in your hand, and there is one on the board.
Set-upThe process whereby strong winds blowing down the length of a lake cause water to "pile up" at the downwind end, raising water levels there and lowering…
Severe IcingThe rate of ice accumulation on an aircraft is such that de-icing/anti-icing equipment fails to reduce or control the hazard.
Severe Local StormA convective storm that usually covers a relatively small geographic area, or moves in a narrow path, and is sufficiently intense to threaten life and/or…
Severe Local Storm WatchAn alert issued by the National Weather Service for the contiguous U.S. and its adjacent waters of the potential for severe thunderstorms or tornadoes.
Severe ThunderstormA thunderstorm that produces a tornado, winds of at least 58 mph (50 knots), and/or hail at least ¾" in diameter.
Severe Thunderstorm WarningThis is issued when either a severe thunderstorm is indicated by the WSR-88D radar or a spotter reports a thunderstorm producing hail 3/4 inch or larger…
Severe Thunderstorm WatchThis is issued by the National Weather Service when conditions are favorable for the development of severe thunderstorms in and close to the watch area.
Severe Weather AnalysisThis WSR-88D radar product provides 3 base products (reflectivity (SWR), radial velocity (SWV), and spectrum width (SWW)) at the highest resolution…
Severe Weather Potential StatementThis statement is designed to alert the public and state/local agencies to the potential for severe weather up to 24 hours in advance.
Severe Weather ProbabilityThis WSR-88D radar product algorithm displays numerical values proportional to the probability that a storm will produce severe weather within 30 minutes.
Severe Weather StatementA National Weather Service product which provides follow up information on severe weather conditions (severe thunderstorm or tornadoes) which have…
Sewage treatment (primary)Mechanical treatment of sewage in which large solids are filtered out by screens and suspended solids settle out as sludge in a sedimentation tank.
Shale oilSlow-flowing, dark brown, heavy oil obtained when kerogen in oil shale is vaporized at high temperatures and then condensed.
Shallow FogFog in which the visibility at 6 feet above ground level is 5/8ths statute mile or more and the apparent visibility in the fog layer is less than 5/8ths…
ShearLiterally the sliding of one layer across another, with deformation and fracturing in the direction parallel to the movement.
Sheet FlowFlow that occurs overland in places where there are no defined channels, the flood water spreads out over a large area at a uniform depth.
Sheet iceIce formed by the freezing of liquid precipitation or the freezing of melted solid precipitation (see snow depth)
Shelf CloudA low, horizontal wedge-shaped arcus cloud, associated with a thunderstorm gust front (or occasionally with a cold front, even in the absence of…
Shore iceAn ice sheet in the form of a long border attached to the bank or shore; border ice.
Short Term ForecastA product used to convey information regarding weather or hydrologic events in the next few hours.
Short Ton2000 pounds. A ton, as commonly used in the U.S. and Canada.
Short Wave Fade (SWF)In solar-terrestrial terms, a particular ionospheric solar flare effect under the broad category of sudden ionospheric disturbances (SIDs) whereby…
Short-Fuse WarningA warning issued by the NWS for a local weather hazard of relatively short duration.
ShortwaveAlso known as Shortwave Trough; a disturbance in the mid or upper part of the atmosphere which induces upward motion ahead of it.
shortwave irradianceThe rate at which radiant energy, at wavelengths between 0.4 and 4 µm, is being transferred across an area of a surface (real or imaginary) in a…
shortwave net radiationThe difference between upwelling and downwelling broadband shortwave radiation.
shortwave radianceA measure of the intrinsic radiant energy flux intensity, at wavelengths between 0.
Shortwave RadiationIn solar-terrestrial terms, shortwave radiation is a term used to describe the radiant energy emitted by the sun in the visible and near-ultraviolet…
shortwave spectral irradianceThe rate at which radiant energy, at specrally-resolved wavelengths between 0.4 and 4 µm, is being emitted upwards and downwards into a radiation field…
Shortwave TroughAlso called Shortwave; A disturbance in the mid or upper part of the atmosphere which induces upward motion ahead of it.
Showalter Index(Abbrev. SWI) - a stability index used to determine thunderstorm potential. The SWI is calculated by lifting an air parcel adiabatically from 850 mb to…
ShowerA descriptor, SH, used to qualify precipitation characterized by the suddenness with which they start and stop, by the rapid changes of intensity, and…
Siberian HighSiberian High An area of high pressure which forms over Siberia in winter, and which is particularly apparent on mean charts of sea-level pressure.
SidelobeA secondary energy maximum located outside the main radar beam. Typically, it contains a small percentage of energy compared to the main lobe, but it may…
Signal-to-Noise RatioA specifically produced response (signal) compared to the response level (noise) when no specific stimulus (activity) is present.
Significant Wave HeightThe average height of the one-third highest waves of a given wave group.
Significant Weather OutlookA narrative statement produced by the National Weather Service, frequently issued on a routine basis, to provide information regarding the potential of…
Single Cell ThunderstormThis type of thunderstorm develops in weak vertical wind shear environments. On a hodograph, this would appear as a closely grouped set of random dots…
single-column modeling (SCM)(SCM)An approach to the development and testing of cloud formation and parameterizations.
SinkAny process, activity, or mechanism which removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere.
SITOR(SImplex Teletype Over Radio) - a means of transmitting text broadcasts over radio. The U.S.
sky brightness temperatureA descriptive measure of radiation in terms of the temperature of a hypothetical black body emitting an identical amount of radiation at the same…
Sky ConditionUsed in a forecast to describes the predominant/average sky condition based upon octants (eighths) of the sky covered by opaque (not transparent) clouds.
SKYWARNA nationwide network of volunteer weather spotters who report to and are trained by the National Weather Service.