PNSPublic Information Statement - a narrative statement issued by a National Weather Service Forecast Office that can be used for: 1) A current or expected…
POHProbability of Hail - a product from the NEXRAD hail detection algorithm that estimates the likelihood that hail is present in a storm.
Point PrecipitationPrecipitation at a particular site, in contrast to the mean precipitation over an area.
Point sourceAny discernible, confined, or discrete conveyance from which pollutants are or may be discharged, including, but not limited to, any pipe, ditch, channel…
Polar Cap Absorption (PCA)In solar-terrestrial terms, an anomalous condition of the polar ionosphere whereby HF and VHF (3 - 300 MHz) radiowaves are absorbed, and LF and VLF (3 -…
Polar dayPolar day In polar regions, the portion of the year when the Sun is continuously in the sky.
Polar explorerPolar explorer A person working for a long time at one of the polar observing stations. Russian word is "polyarnik."
Polar FrontA semipermanent, semicontinuous front that separates tropical air masses from polar air masses.
Polar JetMarked by a concentration of isotherms and strong vertical shear, this jet is the boundary between the polar air and the subtropical air.
Polar Jet StreamUsed interchangably with Polar Jet; a jet stream marked by a concentration of isotherms and strong vertical shear, this jet is the boundary between the…
Polar lowPolar low Small, shallow depression which forms mainly in winter over some high-latitude seas within a polar or arctic air mass.
Polar nightPolar night In polar regions, the portion of the year when the Sun does not rise above the horizon.
Polar Orbiting SatelliteA weather satellite which travels over both poles each time it orbits the Earth. It orbits about 530 miles (850 km) above the Earth's surface.
Polar vortexPolar vortex Large-scale cyclonic circulation in the middle and upper troposphere centered generally in the polar regions.
Polarization RadarA radar which takes advantage of ways in which the transmitted waves' polarization affect the backscattering.
PollutantAny inorganic or organic substance that contaminates air, water or soil. Generally, any substance introduced into the environment that adversely affects…
PollutionA resource that is out of place. Generally, the presence of matter or energy whose nature, location or quantity produces undesired environmental effects.
Polyvinyl Chloride (PVC)A type of plastic used to make pipe and fittings for water distribution and irrigation.
Pondage(1) The holding back of water for later release for power development above the dam of a hydroelectric plant to (a) equalize daily or weekly fluctuations…
PondingIn flat areas, runoff collects, or ponds in depression and cannot drain out. Flood waters must infiltrate slowly into the soil, evaporate, or be pumped…
PoolA deep area of a stream between rapids or where the current is slow.
Pool HeightThe height of the water behind a dam. (Various datums may be used and various pool heights may be used, e.g., conservation pool, flood control pool, etc.)
POPContraction of "Repopulation", often used as a shortened term for the re-spawn of monsters.
Popcorn ConvectionSlang for showers and thunderstorms that form on a scattered basis with little or no apparent organization, usually during the afternoon in response to…
Positive AreaThe area on a sounding representing the layer in which a lifted parcel would be warmer than the environment; thus, the area between the environmental…
Positive Cloud to Ground LightningA CG flash that delivers positive charge to the ground, as opposed to the more common negative charge.
positive feedbackthe process in which an initial change will bring about an additional change in the same direction.
Positive Vorticity Advection(Abbrev. PVA) - Advection of higher values of vorticity into an area, which often is associated with upward motion (lifting) of the air.
Positive-tilt TroughAn upper level system which is tilted to the east with increasing latitude (i.e., from southwest to northeast).
Post-Flare LoopsIn solar-terrestrial terms, a loop prominence system often seen after a major two-ribbon flare, which bridges the ribbons.
Post-storm ReportA report issued by a local National Weather Service office summarizing the impact of a tropical cyclone on it's forecast area.
Post-tropical CycloneA former tropical cyclone. This generic term describes a cyclone that no longer possesses sufficient tropical characteristics to be considered a tropical…
Potential TemperatureThe temperature a parcel of dry air would have if brought adiabatically (i.e., without transfer of heat or mass) to a standard pressure level of 1000 mb.
Potential VorticityThis plays an important role in the generation of vorticity in cyclogenesis, especially along the polar front.
PowerAuthority to do. One has the power to do something if he is of legal age. Also, used as "powers," the term refers to authority granted by one person to…
Pre-Frontal TroughAn elongated area of relatively low pressure preceding a cold front that is usually associated with a shift in wind direction.
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…
PrecessionThe comparatively slow torquing of the orbital planes of all satellites with respect to the Earth's axis, due to the bulge of the Earth at the equator…
precession (of the equinoxes)the slow clockwise motion of the equinoxes along the path of the earth's orbit due to the wobble of the earth's axis.
Precipitable WaterMeasure of the depth of liquid water at the surface that would result after precipitating all of the water vapor in a vertical column over a given…
PrecipitationThe total measurable amount of water received in the form of snow, rain, drizzle, hail, and sleet.
Precipitation AttenuationThe loss of energy that radar beam experiences as it passes through an area of precipitation.
Precipitation ModeThe standard, or default, operational mode of the WSR-88D. The radar automatically switches into precipitation mode from clear-air mode if the measured…
Precipitation Processing SystemThe WSR-88D system that generates 1-hour running, 3-hourly, and running storm total precipitation accumulations.
PrecisionThe accuracy with which a number can be represented, i.e., the number of digits used to represent a number.
Predominant WindThe wind that prevails and generates the local component of the significant sea conditions across the forecast area.
preliminary dataData that have not necessarily been subjected to review, quality control and/or documentation by a responsible investigator.
Preliminary ReportNow known as the "Tropical Cyclone Report". A report summarizing the life history and effects of an Atlantic or eastern Pacific tropical cyclone.
Prescribed burningDeliberate setting and careful control of surface fires in forests to help prevent more destructive fires and to kill off unwanted plants that compete…
Prescribed FireA management ignited or natural wildland fire that burns under specified conditions where the fire is confined to a predetermined area and produces the…
Present MovementThe best estimate of the movement of the center of a tropical cyclone at a given time and given position.
Present WeatherThe type of weather observed at the reporting time. These conditions may include types and intensity of precipitation such as light rain or heavy snow, as…
PressureThe load divided by the area over which it acts.
Pressure AltimeterAn aneroid barometer calibrated to indicate altitude in feet instead of units of pressure.
Pressure AltitudeThe altitude in standard atmosphere at which a given pressure will be observed.
Pressure ChangeThe net difference between the barometric pressure at the beginning and ending of a specified interval of time, usually the three hour period preceding an…
Pressure CharacteristicThe pattern of the pressure change during the specified period of time, usually the three hour period preceding an observation.
Pressure CoupletIt is an area where you have a high pressure area located adjacent to a low pressure area.
Pressure Falling RapidlyA decrease in station pressure at a rate of 0.06 inch of mercury or more per hour which totals 0.02 inch or more.
Pressure GageA device for registering the pressure of solids, liquids, or gases. It may be graduated to register pressure in any units desired.
Pressure GradientThe amount of pressure change occurring over a given distance.
Pressure Gradient ForceA three-dimensional force vector operating in the atmosphere that accelerates air parcels away from regions of high pressure and toward regions of low…
Pressure HeadThe amount of force or pressure created by a depth of one foot of water.
Pressure IceFloating sea, river, or lake ice that has been deformed, altered, or forced upward in pressure ridges by the lateral stresses of any combination of wind…
Pressure Induced WaveA rare type of wave that does not develop from wind or seismic activity. Instead, these waves develop as a pressure perturbation moves over the water…
Pressure JumpA sudden, sharp increase in atmospheric pressure, typically occurring along an active front and preceding a storm.
Pressure Rising RapidlyAn increase in station pressure at a rate of 0.06 inch of mercury or more per hour which totals 0.02 inch or more.
Pressure TendencyThe character and amount of atmospheric pressure change during a specified period of time, usually 3-hour period preceding an observation.
Pressure UnsteadyA pressure that fluctuates by 0.03 inch of mercury or more from the mean pressure during the period of measurement.
Pressure-driven ChannelingChanneling of wind in a valley by synoptic-scale pressure gradients superimposed along the valley's axis. Compare forced channeling.
Prevailing VisibilityThe visibility that is considered representative of conditions at the station; the greatest distance that can be seen throughout at least half the horizon…
prevailing windThe wind direction most frequently observed during a given period.
Prevailing WindsA wind that consistently blows from one direction more than from any other.
Prevention of Significant DeteriorationA program, specified in the Clean Air Act, whose goal is to prevent air quality from deteriorating significantly in areas of the country that are…