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Active ProminenceIn solar-terrestrial terms, a prominence displaying material motion and changes
in appearance over a few minutes of time.Active Prominence Region (APR)In solar-terrestrial terms, a portion of the solar limb displaying active prominences.Advanced Baseline Imager (ABI)A moderate resolution imaging system on the GOES and Himawari family of satellites.Aeration ZoneA portion of the lithosphere in which the functional interstices of permeable rock or earth are not filled with water under hydrostatic pressure. The interstices either are not filled with water or are filled with water that is no held by capillarity.Airborne Snow Survey ProgramIn hydrologic terms, Center (NOHRSC) program that makes airborne snow water equivalent and soil moisture measurements over large areas of the country that are subject to severe and chronic snowmelt flooding.AnemometerAn instrument used for measuring the speed of the wind.Aneroid BarometerAn instrument for measuring atmospheric pressure in which a needle, attached to the top of an evacuated box, is deflected as changes in atmospheric pressure cause the top of the box to bend in or out.
AnticyclogenesisThe formation or intensification of an anticyclone or high pressure center.AnticycloneA large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern HemisphereBanner CloudA cloud plume often observed to extend downwind behind isolated mountain peaks, even on otherwise cloud-free days.Baroclinic ZoneA region in which a temperature gradient exists on a constant pressure surface. Baroclinic zones are favored areas for strengthening and weakening systems; barotropic systems, on the other hand, do not exhibit significant changes in intensity. Also, wind shear is characteristic of a baroclinic zone.BrightnessA basic visual sensation describing the amount of light that appears to emanate from an object, or more precisely, the luminance of an object Capillary ZoneUsed interchangably with Capillary Fringe; the soil area just above the water table where water can rise up slightly through the cohesive force of capillary action. This layer ranges in depth from a couple of inches, to a few feet, and it depends on the pore sizes of the materials.ChannelIn hydrologic terms, also known as Watercourse; an open conduit either naturally or artificially created which periodically, or continuously contains moving water, or forms a connecting link between two bodies of water. River, creek, run, branch, anabranch, and tributary are some of the terms used to describe natural channels. Natural channels may be single or braided. Canal and floodway are some of the terms used to describe artificial channels.Channel InflowIn hydrologic terms, water, which at any instant, is flowing into the channel system form surface flow, subsurface flow, base flow, and rainfall that has directly fallen onto the channel.Channel LeadIn hydrologic terms, an elongated opening in the ice cover caused by a water current.Channel RoutingIn hydrologic terms, the process of determining progressively timing and shape of the flood wave at successive points along a river.Channeled High WindsIn mountainous areas or in cities with tall buildings, air may be channeled through constricted passages producing high winds. Santa Ana winds and winds through passes from the cold Alaskan interior to the sea are examples of these winds. Channeled high winds are local in nature but can be extremely strong. These winds generally occur in well-defined areas.ChannelizationIn hydrologic terms, the modification of a natural river channel; may include deepening, widening, or straightening.Cold Air FunnelA funnel cloud or (rarely) a small, relatively weak tornado that can develop from a small shower or thunderstorm when the air aloft is unusually cold (hence the name). They are much less violent than other types of tornadoes.Combined SeasGenerally referred to as SEAS. Used to describe the combination or interaction of wind waves and swells in which the separate components are not distinguished. This includes the case when swell is negligible or is not considered in describing sea state. Specifically, Seas2 = S2+W2 where S is the height of all swell components and W is the height of the wind wave components. When used, SEAS should be considered as being the same as the significant wave height.
Condensation FunnelA funnel-shaped cloud associated with rotation and consisting of condensed water droplets (as opposed to smoke, dust, debris, etc.).Cone of DepressionIn hydrologic terms, the 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. The volume of the cone will vary with the rate of withdrawal of water. Also called the Cone of Influence. Cone of InfluenceSame as Cone of Depression; in hydrologic terms, the 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. The volume of the cone will vary with the rate of withdrawal of water. Confined Ground WaterIn hydrologic terms, ground water held under an aquiclude or an aquifuge, called artesian if the pressure is positive.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.Corner EffectsA small-scale convergence effect that can be quite severe. It occurs around
steep islands and headlands.Cyclogenesis(Abbrev. CYCLGN) - The formation or intensification of a cyclone or low-pressure storm system.Cyclone(abbrev. CYC) - A large-scale circulation of winds around a central region of low atmospheric pressure, counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere.DATANETIn hydrologic terms, it is the hydrologic Data Network Analysis Software.Deformation ZoneThe change in shape of a fluid mass by variations in
wind, specifically by stretching and/or shearing. Deformation is a primary factor in frontogenesis (evolution of fronts) and frontolysis
(decay of fronts). Dividing StreamlineIn the blocked flow region upwind of a mountain barrier, the streamline that separates the blocked flow region near the ground from the streamlines above which go over the barrier.Dividing Streamline HeightThe height above ground of the dividing streamline, as measured far upwind of a mountain barrier. See dividing streamline.DrainerA valley or basin from which air drains continuously during nighttime rather than becoming trapped or pooled.
Dry LineA boundary separating moist and dry air masses, and an important factor in
severe weather frequency in the Great Plains. It typically lies north-south across
the central and southern high Plains states during the spring and early summer,
where it separates moist air from the Gulf of Mexico (to the east) and dry desert
air from the southwestern states (to the west). The dry line typically advances
eastward during the afternoon and retreats westward at night. However, a strong
storm system can sweep the dry line eastward into the Mississippi Valley, or
even further east, regardless of the time of day.
A typical dry line passage results in a sharp drop in humidity (hence the name),
clearing skies, and a wind shift from south or southeasterly to west or
southwesterly. (Blowing dust and rising temperatures also may follow, especially
if the dry line passes during the daytime. These changes occur in reverse order
when the dry line retreats westward. Severe and sometimes tornadic
thunderstorms often develop along a dry line or in the moist air just to the east of
it, especially when it begins moving eastward.Dry Line BulgeA bulge in the dry line, representing the area where dry air is advancing most strongly at lower levels. Severe weather potential is increased near and ahead of a dry line bulge.Dry Line StormAny thunderstorm that develops on or near a dry line.Duration of SunshineThe amount of time sunlight was detected at a given point.Energy DissipatorIn hydrologic terms, a structure which slows fast-moving spillway flows in order to prevent erosion of the stream channel.Energy Helicity IndexAn index that incorporates vertical shear and instability, designed for the
purpose of forecasting supercell thunderstormsEngineer's LevelA 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.Entrainment ZoneA 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.Equi-Potential LineIn 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.Eruptive Prominence on Limb (EPL)In solar-terrestrial terms, a solar prominence that becomes activa-
ted and is seen to ascend from the sun.Esturine watersIn 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 ZoneIn hydrologic terms, the area near the coastline that consists of esturaries and coastal saltwater wetlandsExtratropical CycloneA 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.Fall LineA skiing term, indicating the line of steepest descent of a slope.Filament ChannelA broad pattern of fibrils in the chromosphere, marking
where a filament may soon form or where a filament recently
disappeared.Firn LineIn hydrologic terms, the highest level to which the fresh snow on a glacier's surface retreats during the melting season. The line separating the
accumulation area from the ablation areaFlanking LineA line of cumulus or towering cumulus clouds connected to and extending
outward from the most active part of a supercell, normally on the southwest side. The line normally
has a stair-step appearance, with the tallest clouds closest to the main stormForced ChannelingChanneling of upper winds along a valley's axis when upper winds are diverted by the underlying topography. Compare pressure-driven channeling.Fracture ZoneIn hydrologic terms, an area which has a great number of fractures.Frontogenesis1. The initial formation of a front or frontal zone. 2. In general, an increase in the horizontal gradient of an airmass property, principally density, and the development of the accompanying features of the wind field that typify a front.Funnel CloudA condensation funnel extending from the base of a towering cumulus or Cb, associated with a rotating column of air that is not in contact with the ground (and hence different from a tornado). A condensation funnel is a tornado, not a funnel cloud, if either a) it is in contact with the ground or b) a debris cloud or dust whirl is visible beneath it.FunnellingThe process whereby wind is forced to flow through a narrow opening between adjacent land areas, resulting in increased wind speed. General CirculationThe totality of large-scale organized motion for the entire global atmosphere.General Circulation Models(GCMs) - These computer simulations reproduce the Earth's weather patterns and can be used to predict change in the weather and climate.General WindLand management agency term for winds produced by synoptic-scale pressure systems on which smaller-scale or local convective winds are superimposed.Geomagnetic ElementsIn solar-terrestrial terms, the components of the geomagnetic field at the surface of the earth. In SESC use, the northward and eastward components are often called the H and D components, where the D component is expressed in gammas and is derived from D (the declination angle) using the small angle approximation.Geomagnetic FieldThe magnetic field observed in and around the earth.
The intensity of the magnetic field at the earth's surface is
approximately 0.32 gauss at the equator and 0.62 gauss at the
north poleGeomagnetic StormIn solar-terrestraial terms, a worldwide disturbance of the earth's magnetic field,
distinct from regular diurnal variations.
Minor Geomagnetic Storm: A storm for which the Ap index was
greater than 29 and less than 50.
Major Geomagnetic Storm: A storm for which the Ap index was
greater than 49 and less than 100.
Severe Geomagnetic Storm: A storm for which the Ap index was
100 or more.
Initial Phase: Of a geomagnetic storm, that period when there
may be an increase of the middle-latitude horizontal
intensity (H).
Main Phase: Of a geomagnetic storm, that period when the hori-
zontal magnetic field at middle latitudes is generally
decreasing.
Recovery Phase: Of a geomagnetic storm, that period when the
depressed northward field component returns to normal levels.Great Lakes Marine Forecast (MAFOR)A National Weather Service coded summary appended to each of the Great Lakes Open Lakes forecasts. Green LineThe green line is one of the strongest (and first-recognized)
visible coronal lines. It identifies moderate temperature regions
of the CORONA.H-component of the Geomagnetic Field(Geomagnetic Elements) In solar-terrestrial terms, the components of the geomagnetic field at the surface of the earth. In SESC use, the
northward and eastward components are often called the H and D components, where the D component is
expressed in gammas and is derived from D (the declination angle) using the small angle approximation.Hague LineThe North Atlantic boundary between the U.S. and Canada fishing waters as determined by the World Court in The Hague, Netherlands.Haines IndexThis is also called the Lower Atmosphere Stability Index. It is computed from the
morning (12Z) soundings from RAOB stations across North America. The index is composed of a
stability term and a moisture term. The stability term is derived from the temperature difference at
two atmosphere levels. The moisture term is derived from the dew point depression at a single
atmosphere level. This index has been shown to be correlated with large fire growth on initiating
and existing fires where surface winds do not dominate fire behavior. The Haines Indices range
from 2 to 6 for indicating potential for large fire growthHeight Above the Nearest Drainage (HAND)A relative elevation methodology used in inundation mapping, which determines the height of every point on a land surface above the nearest stream reach to which it drains.High Energy EventIn solar-terrestrial terms, flares (class two or more) with outstanding Centimetric
Bursts and SID. High Energy Protons are reported at the Earth in
case of most of these events occurring on the western part of solar
disk. (Class X flares)Hurricane(abbrev. HURCN) A tropical cyclone in the Atlantic, Caribbean Sea, Gulf of Mexico, or eastern Pacific, which the maximum 1-minute sustained surface wind is 64 knots (74 mph) or greater.Hurricane Force Wind WarningA warning for sustained winds, or frequent gusts, of 64 knots (74 mph) or greater, either predicted or occurring, and not directly associated with a tropical
cyclone. Hurricane Force Wind WatchA watch for an increased risk of a hurricane force wind event for sustained surface winds, or frequent gusts, of 34 knots 64 knots (74 mph) or greater, but its occurrence, location, and/or timing is still uncertain.Hurricane Local StatementA public release prepared by local National Weather Service offices in or near a
threatened area giving specific details for its county/parish warning area on
(1)
weather conditions
(2) evacuation decisions made by local officials
(3) other
precautions necessary to protect life and property.Hurricane SeasonThe part of the year having a relatively high incidence of tropical cyclones. In the Atlantic, Caribbean, and Gulf of Mexico, and central North Pacific, the hurricane season is the period from June through November; in the eastern Pacific, May 15 through November 30. Tropical cyclones can occur year-round in any basin.Hurricane WarningAn announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds. The warning can remain in effect when dangerously high water or a combination of dangerously high water and waves continue, even though winds may be less than hurricane force. Hurricane WatchAn announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.Hydraulic Grade LineIn hydrologic terms, a line whose plotted ordinate position represents the sum of pressure head plus elevation head for the various positions along a
given fluid flow path, such as along a pipeline or a ground water streamline.Index of WetnessThe ratio of precipitation for a given year over the mean annual precipitation.International Date LineThe line of longitude located at 180 degrees East or West (with a few local deviations) where the date changes by a day. West of the line it is one day later than east of the line.Interplanetary Magnetic Field(abbrev. IMF) In solar-terrestrial terms, the magnetic field carried with the
solar wind.Intertropical Convergence Zone(ITCZ) The region where the northeasterly and southeasterly trade winds converge, forming an often continuous band of clouds or thunderstorms near the equator. IsochroneA line on a chart connecting equal times of occurrence of an event. In a weather analysis, a sequence plotted on a map of the frontal positions at several different
observation times would constitute a set of isochrones.Kinetic EnergyEnergy that a body has as a result of its motion. Mathematically, it is defined as one-half the product of a body's mass and the square of its speed (KE = 1/2 * mass * velocity squared).Lightning ChannelThe irregular path through the air along which a lightning discharge occurs.
A typical discharge of flash between the ground and the cloud is actually a composite flash
which is composed of several sequential lightning strokes, each of which is initiated by a leader
and terminated by a return streamer.Line Echo Wave Pattern(abbrev. LEWP) A radar echo pattern formed when a segment of a line of thunderstorms surges forward at an accelerated rate.Line SourceAn array of pollutant sources along a defined path that can be treated in dispersion models as an aggregate uniform release of pollutants along a line. Example: the sum of emissions from individual cars traveling down a highway can be treated as a line source. Compare area source and point source.Littoral ZoneIn hydrologic terms, the area on, or near the shore of a body waterLoop Prominence System(abbrev. LPS) In solar-terrestrial terms, a system of loop prominences associated with
major flares.Magnetic BayIn solar-terrestrial terms, a relatively smooth excursion of the H (horizontal) component
of the geomagnetic field away from and
returning to quiet levels.MagnetogramIn solar-terrestrial terms, solar magnetograms are a graphic representation of solar magnetic field strengths and polarityMagnetopauseIn solar-terrestrial terms, the boundary layer between the solar wind and the magnetosphere.MagnetosphereIn solar-terrestrial terms, the magnetic cavity surrounding the earth, carved out of the
passing solar wind by virtue of the geomagnetic field, which prevents, or at least impedes, the direct entry of the solar wind
plasma into the cavityMajor HurricaneA hurricane which reaches Category 3 (sustained winds greater than 110 mph) on the Saffir/Simpson Hurricane Scale. Marine InversionTemperature inversion produced when cold marine air underlies warmer air.Marine PushA replacement of the current air mass with air from off the ocean. Temperatures are much cooler and relative humidities much higher. The air mass is generally much more stable in this situation.Marine Small Craft Thunderstorm AdvisoryA marine warning issued by Environment Canada
Atmospheric Environment Branch when the possibility of thunderstorms is greater than 40
percent.Marine Small Craft Wind WarningA marine warning issued by Environment Canada
Atmospheric Environment Branch for winds which are forecasted to be in the 20-33 knot range
inclusive.Marine Weather StatementA National Weather Service product to provide mariners with details on significant or potentially hazardous conditions not otherwise covered in existing marine warnings and forecasts. Marine weather statements are also used to supplement special marine warnings.Marine ZoneSpecific, defined over-water areas contained in the various NWS marine forecasts. These are the equivalent of "zones" in the public forecast program. Maximum Sustained Surface WindWhen applied to a particular weather system, refers to the highest one-minute average wind (at an elevation of 10 meters with an unobstructed exposure) associated with that weather system at a particular point in time. Mesocyclone(abbrev. MESO)- A storm-scale region of rotation, typically around 2-6 miles in diameter and often found in the right rear flank of a supercell (or often on the eastern, or front, flank of an HP storm). The circulation of a mesocyclone covers an area much larger than the tornado that may develop within it. Properly used, mesocyclone is a radar term; it is defined as a rotation signature appearing on Doppler radar that meets specific criteria for magnitude, vertical depth, and duration. It will appear as a yellow solid circle on the Doppler velocity products. Therefore, a mesocyclone should not be considered a visually-observable phenomenon (although visual evidence of rotation, such as curved inflow bands, may imply the presence of a mesocyclone).MesonetA regional network of observing stations (usually surface stations) designed to diagnose mesoscale weather features and their associated processes.Mount Wilson Magnetic ClassificationsIn solar-terrestrial terms, a classification system for sunspots:
- Alpha: Denotes a unipolar sunspot group.
- Beta: A sunspot group having both positive and negative magnetic polarities, with a simple and distinct division between the polarities.
- Beta-Gamma: A sunspot group that is bipolar but in which no continuous line can be drawn separating spots of opposite polarities.
- Delta: A complex magnetic configuration of a solar sunspot group consisting of opposite polarity umbrae within the same penumbra.
- Gamma: A complex active region in which the positive and negative polarities are so irregularly distributed as to prevent classification as a bipolar group.
National Hurricane Center One of three branches of the Tropical Prediction Center (TPC). This center maintains a continuous watch on tropical cyclones over the Atlantic, Caribbean, Gulf of Mexico, and the Eastern Pacific from 15 May through November 30. The Center prepares and distributes hurricane watches and warnings for the general public, and also prepares and distributes marine and military advisories for other users. During the "off-season" NHC provides training for U.S. emergency managers and representatives from many other countries that are affected by tropical cyclones. NHC also conducts applied research to evaluate and improve hurricane forecasting techniques, and is involved in public awareness programs.National Hurricane Operations Plan(NHOP) - The NHOP is issued annually by the Federal Coordinator for Meteorological Services and Supporting Research. It documents interdepartmental agreements relating to tropical cyclone observing, warning, and forecasting services. National Hurricane Center (NHC), Central Pacific Hurricane Center (CPHC), and the JTWC serve as the principal offices in coordinating the day-to-day activities of the NWS in support of the Plan in their region of responsibility. NENortheastNeap TideA minimum tide occurring at the first and third quarters of the moon.Nearshore Forecast(NSH) - National Weather Service seasonal marine forecasts for an areas of the Great Lakes extending from a line approximating mean low water datum along the coast or an island, including bays, harbors, and sounds, out to 5 nm. These forecasts are normally issued from Daylight Savings Time ~April 7 through December 31, though the dates may be shortened or extended based on local/regional requirements. NECNecessaryNEGNegativeNegative Vorticity Advection(Abbrev. NVA) - the advection of lower values of vorticity into an area.Negative-tilt TroughAn upper level system which is tilted to the west with increasing latitude (i.e., with an axis from southeast to northwest). A negative-tilt trough often is a sign of a developing or intensifying system.NELYNortheasterlyNERNNortheasternNESDISNational Environmental Satellite, Data, and Information Service. NESDIS collects, processes, stores, analyzes, and disseminates various types of hydrologic, meteorologic, and oceanic data.
NESDIS is also responsible for the development of analytical and descriptive products so as to meet the needs of it’s users. Net All-Wave RadiationThe net or resultant value of the upward and downward longwave and shortwave radiative fluxes through a plane at the earth-atmosphere interface; a component of the surface energy budget.Net RainfallIn hydrologic terms, the portion of rainfall which reaches a stream channel or the concentration point as direct surface flow.Neutral LineThe line that separates longitudinal magnetic fields of opposite polarity.Neutral StabilityAn atmospheric condition that exists in unsaturated air when the environmental lapse rate equals the dry adiabatic rate, or in saturated air when the environmental lapse rate equals the moist adiabatic rate.NEWDNortheastwardNEXRADNEXt Generation RADar. A NWS network of about 140 Doppler radars operating nationwide.Occluded MesocycloneA mesocyclone in which air from the rear-flank downdraft has completely enveloped the circulation at low levels, cutting off the inflow of warm unstable low-level air.Outflow ChannelIn hydrologic terms, a natural stream channel which transports reservoir releases.OzoneA form of oxygen, O3. A powerful oxidizing agent that is considered a pollutant in the lower troposphere but an essential chemical in the stratosphere where it protects the earth from high-energy ultraviolet radiation from the sun.Ozone Action DayA "heads-up" message issued by the Department of Natural Resources (DNR) through the National Weather Service when ozone levels may reach dangerous levels the next day. This message encourages residents to prevent air pollution by postponing the use of lawn mowing, motor vehicles, boats, as well as filling their vehicle gas tanks.Ozone AdvisoryIt is issued by the Department of Natural Resources (DNR) through the National Weather Service when ozone levels reach 100. Ozone levels above 100 are unhealthy for people with heat and/or respiratory ailments.Ozone HoleA severe depletion of stratospheric ozone over Antarctica that occurs each spring. The possibility exists that a hole could form over the Arctic as well. The depletion is caused by a chemical reaction involving ozone and chlorine, primarily from human produced sources, cloud particles, and low temperatures.Ozone LayerAn atmospheric layer that contains a high proportion of oxygen that exists as ozone. It acts as a filtering mechanism against incoming ultraviolet radiation. It is located between the troposphere and the stratosphere, around 9.5 to 12.5 miles (15 to 20 kilometers) above the earth's surface.Penetrating TopSame as Overshooting Top; a dome-like protrusion above a thunderstorm anvil, representing a very strong updraft and hence a higher potential for severe weather with that storm. A persistent and/or large overshooting top (anvil dome) often is present on a supercell.
A short-lived overshooting top, or one that forms and dissipates in cycles, may indicate the presence of a pulse storm. Pervious ZoneIn hydrologic terms, a part of the cross section of an embankment dam comprising material of high permeabilityPlanetary Boundary LayerThe layer within the atmosphere between 1 km and the earth's surface where friction affects wind speed and wind direction.PPINEPlan Position Indicates No Echoes, referring to the fact that a radar detects no precipitation within its range. An intensity-modulated display on which echo signals are shown in plain view with range and azimuth angle displayed in polar coordinates, forming a map-like display. Each PPI is taken at a single, fixed elevation angle, and thus forms a cone of coverage in space. PPIs may be run in sequence, creating a "volume scan".Pre-Frontal Squall LineA line of thunderstorms that precedes an advancing cold front.Pre-Hurricane Squall LineIt is often the first serious indication that a hurricane is approaching. It is a generally a straight line and resembles a squall-line that occurs with a mid-latitude cold front. It is as much as 50 miles or even more before the first ragged rain echoes of the hurricane's bands and is usually about 100 to 200 miles ahead of the eye, but it has been observed to be as much as 500 miles ahead of the eye in the largest hurricanes.Pressure-driven ChannelingChanneling of wind in a valley by synoptic-scale pressure gradients superimposed along the valley's axis. Compare forced channeling.Probability of Tropical Cyclone ConditioThe probability, in percent, that the cyclone center will pass within 50 miles to the
right or 75 miles to the left of the listed location within the indicated time period
when looking at the coast in the direction of the cyclone's movement.Prominence A term identifying cloud-like features in the solar atmosphere.
The features appear as bright structures in the CORONA above the
solar LIMB and as dark FILAMENTs when seen projected against the
solar DISKPuget Sound Convergence ZoneA situation where wind forced around the Olympic Mountains converges over the Puget Sound. Causes extreme variability in weather conditions around Seattle, Washington with some areas of sunshine and others in clouds and rain.Quiescent Prominence (Filament) Long, sheet-like prominences nearly vertical
to the solar surfaceRadar Product Generator (RPG)The RPG is the computer in the NEXRAD system that receives polar-coordinate base radar data from the RDA and processes these data into end-user products. Algorithms are utilized for pattern-recognition, rainfall estimation, computation of VIL and other products. The RPG communicates these products to end-users. A specific subset of available products is always generated for the NIDS vendors for distribution outside of the NWS, DoD, and FAA. Other products are generated by the RPG upon request from a PUP.Rankine VortexVelocity profile for a symmetric circulation in which the inner core is in solid rotation and tangential winds outside the core vary inversely with radial distance from the center.Riparian ZoneIn hydrologic terms, a stream and all the vegetation on its banks.SafetyNET Inmarsat-C SafetyNET is an internationally adopted, automated satellite system for promulgating weather forecasts and warnings, marine navigational warnings and other safety related information to all types vessels and is part of the Global Maritime Distress and Safety System (GMDSS).Saffir-Simpson Hurricane Wind ScaleThe Saffir-Simpson Hurricane Wind Scale is a 1 to 5 categorization based on the hurricane's intensity at the indicated time. The scale provides examples of the type of damage and impacts in the United States associated with winds of the indicated intensity. In general, damage rises by about a factor of four for every category increase. The maximum sustained surface wind speed (peak 1-minute wind at the standard meteorological observation height of 10 m [33 ft] over unobstructed exposure) associated with the cyclone is the determining factor in the scale. The scale does not address the potential for other hurricane-related impacts, such as storm surge, rainfall-induced floods, and tornadoes.
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.Sentinel-1 (S1)A European Space Agency satellite remote sensing mission which images with a 5cm wavelength Synthetic Aperture Radar (SAR).Sentinel-2 (S2)A European Space Agency satellite remote sensing mission which images with a multi-spectral scanner.Special Marine Warning(SMW) A warning product issued for potentially hazardous weather conditions usually of short duration (up to 2 hours) producing sustained marine thunderstorm winds or associated gusts of 34 knots or greater; and/or hail 3/4 inch or more in diameter; and/or waterspouts affecting areas included in a Coastal Waters Forecast, a Nearshore Marine Forecast, or an Great Lakes Open Lakes Forecast that is not adequately covered by existing marine warnings. Also used for short duration mesoscale events such as a strong cold front, gravity wave, squall line, etc., lasting less than 2 hours and producing winds or gusts of 34 knots or greater. SPENESNESDIS Satellite Precipitation EstimatesSquall LineA line of active thunderstorms, either continuous or with breaks, including contiguous precipitation areas resulting from the existence of the thunderstorms.SteepnessIn marine terms, on a buoy report, wave steepness is the ratio of wave height to wave length and is an indicator of wave stability. When wave steepness exceeds a 1/7 ratio, the wave becomes unstable and begins to break.Straight-Line HodographThe name pretty well describes what it looks like on the hodograph. What causes this shape is a steady increase of winds with height (vertical wind shear). This shape of hodograph favors multicell thunderstorms.Straight-line WindsGenerally, any wind that is not associated with rotation, used mainly to differentiate them from tornadic winds.Stratospheric OzoneIn the stratosphere, ozone has beneficial properties where it forms an ozone shield that prevents dangerous radiation from reaching the Earth's surface. Recently, it was discovered that in certain parts of the world, especially over the poles, stratospheric ozone was disappearing creating an ozone hole.Stream lineArrows on a weather chart showing wind speed and direction. The head of the arrow points toward where the wind is blowing and the length of the arrow is proportional to the wind speed. Sometimes shows wind direction and trajectory only. Subtropical CycloneA non-frontal low pressure system that has characteristics of both tropical and extratropical cyclones. This system is typically an upper-level cold low with circulation extending to the surface layer and maximum sustained winds generally occurring at a radius of about 100 miles or more from the center. In comparison to tropical cyclones, such systems have a relatively broad zone of maximum winds that is located farther from the center, and typically have a less symmetric wind field and distribution of convection.Surf ZoneArea of water between the high tide level on the beach and the seaward side of the breaking waves. Surf Zone Forecast(SRF) - A National Weather Service routine or event driven forecast product geared toward non-boating marine users issued for an area extending from the area of water between the high tide level on the beach and the seaward side of the breaking waves. Surface Energy BudgetThe energy or heat budget at the earth's surface, considered in terms of the fluxes through a plane at the earth-atmosphere interface. The energy budget includes radiative, sensible, latent and ground heat fluxes.Sustained OverdraftIn hydrologic terms, long-term withdrawal from the aquifer of more water than is being recharged.Sustained WindWind speed determined by averaging observed values over a two-minute period.TeleconnectionLinkage between changes in atmospheric circulation occurring in widely separated parts of the globe.ThermoclineAs one descends from the surface of the ocean, the temperature remains nearly the same as it was at the surface, but at a certain depth temperature starts decreasing rapidly with depth. This boundary is called the thermocline. In studying the tropical Pacific Ocean, the depth of 20ºC water ("the 20ºC isotherm") is often used as a proxy for the depth of the thermocline. Along the equator, the 20ºC isotherm is typically located at about 50 m depth in the eastern Pacific, sloping downwards to about 150 m in the western Pacific.Thin Line EchoA narrow, elongated, non-precipitating echo. It is usually associated with
thunderstorm outflows, fronts, or other density discontinuities. It is also known as a Fine Line.Tropical CycloneA warm-core, non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters with organized deep convection and a closed surface wind circulation about a well-defined center.Tropical Cyclone Plan of the DayA coordinated mission plan that tasks operational weather reconnaissance requirements during the next 1100 to 1100 UTC day or as required, describes reconnaissance flights committed to satisfy both operational and research requirements, and identifies possible reconnaissance requirements for the succeeding 24-hour period.Tropical Cyclone Position EstimateThe National Hurricane Center issues a position estimate between scheduled advisories whenever the storm center is within 200 nautical miles of U.S. land-based weather radar and if sufficient and regular radar reports are available to the hurricane center. As far as is possible, the position estimate is issued hourly near the beginning of the hour. The location of the eye or storm center is given in map coordinates and distance and direction from a well-known point. Tropical Cyclone UpdateThis brief statement is issued by the National Hurricane Center in lieu of or preceding special advisories to inform of significant changes in a tropical cyclone or the posting or cancellation of watches and warnings.Vadose ZoneThe locus of points just above the water table where soil pores may either contain
air or water. This is also called the zone of aerationVelocity ZonesIn hydrologic terms, areas within the floodplain subject to potential high damage from waves. These sometimes appear on flood insurance rate mapsWave SteepnessThe ratio of wave height to wavelength and is an indicator of wave stability. When wave steepness exceeds a 1/7 ratio; the wave typically becomes unstable and begins to break.West African Disturbance LineA line of convection about 300 miles long, similar to a squall line. It forms over west Africa north of the equator and south of 15 degrees North latitude. It moves faster than an Easterly Wave between 20 and 40 mph. They move off the African coast every 4 to 5 days mainly in the summer. Some reach the American tropics and a few develop into tropical cyclones.Wind Shift LineA long, but narrow axis across which the winds change direction (usually veer).Zone of AerationIn hydrologic terms, the locus of points just above the water table where soil pores may either contain air or water. This is also called the vadose zoneZone of SaturationIn hydrologic terms, the locus of points below the water table where soil pores are filled with water. This is also called the phreatic zoneZoned Embankment DamIn hydrologic terms, an embankment dam which is comprised of zones of selected materials having different degrees of porosity, permeability and
density.
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