There are 29 names in this directory beginning with the letter P.
Pendant Echo
Radar signature generally similar to a hook echo, except that the hook shape is not as well defined.
Polar front
The semi- permanent, semi- continuous front that encircles the northern hemisphere separating air masses of tropical and polar origin
Polar Stratospheric Clouds (PSCs)
High altitude clouds that form in the stratosphere above Antarctica during the Southern Hemisphere winter. Their presence seems to initiate the ozone loss experienced during the ensuing Southern Hemisphere spring.
Polar vortex
A circumpolar wind circulation which isolates the Antarctic continent during the cold Southern Hemisphere winter, heightening ozone depletion.
Pollutant
Strictly too much of any substance in the wrong place or at the wrong time is a pollutant. More specifically, atmospheric pollution may be defined as the - presence of substances in the atmosphere, resulting from man- made activities or from natural processes, causing adverse effects to man and the environment.
POP
Probability of Precipitation. Probability forecasts are subjective estimates of the chances of encountering measurable precipitation at some time during the forecast period.
Popcorn Convection
Clouds, showers and thundershowers that form on a scattered basis with little or no apparent organization, usually during the afternoon in response to diurnal heating.
Positive Area
The area on a sounding representing the layer in which a lifted parcel would be warmer than the environment; thus, the area between the environmental temperature profile and the path of the lifted parcel.
Positive- tilt Trough
An upper level system which is tilted to the east with increasing latitude (i.e., from southwest to northeast). A positive- tilt trough often is a sign of a weakening weather system, and generally is less likely to result in severe weather than a negative- tilt trough if all other factors are equal.
Potential Temperature
The 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.
Precipitation Shaft
A visible column of rain and/or hail falling from a cloud base. When viewed against a light background, heavy precipitation appears very dark gray, sometimes with a turquoise tinge. This turquoise tinge has been commonly attributed to hail, but its actual cause is unknown.
Pressure
The force exerted by the interaction of the atmosphere and gravity. Also known as atmospheric pressure.
Pressure Change
The net difference between pressure readings at the beginning and ending of a specified interval of time.
Pressure Falling Rapidly
A 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 Gradient Force
Force acting on air that causes it to move from areas of higher pressure to areas of lower pressure.
Pressure Rising Rapidly
An 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 Tendency.
The character and amount of atmospheric pressure change during a specified period of time, usually the 3 - hour period preceding an observation.
Pressure Unsteady
A pressure that fluctuates by 0.03 inch of mercury or more from the mean pressure during the period of measurement.
Prevailing Westerlies
Winds in the middle latitudes (approximately 30 degrees to 60 degrees) that generally blow from west to east.
Profiler
An instrument designed to measure horizontal winds directly above its location, and thus measure the vertical wind profile. Profilers operate on the same principles as Doppler radar.
Pulse Storm
A thunderstorm within which a brief period (pulse) of strong updraft occurs, during and immediately after which the storm produces a short episode of severe weather. These storms generally are not tornado producers, but often produce large hail and/or damaging winds. See overshooting top, cyclic storm.
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Pendant Echo
Radar signature generally similar to a hook echo, except that the hook shape is not as well defined.
Polar front
The semi- permanent, semi- continuous front that encircles the northern hemisphere separating air masses of tropical and polar origin
Polar Stratospheric Clouds (PSCs)
High altitude clouds that form in the stratosphere above Antarctica during the Southern Hemisphere winter. Their presence seems to initiate the ozone loss experienced during the ensuing Southern Hemisphere spring.
Polar vortex
A circumpolar wind circulation which isolates the Antarctic continent during the cold Southern Hemisphere winter, heightening ozone depletion.
Pollutant
Strictly too much of any substance in the wrong place or at the wrong time is a pollutant. More specifically, atmospheric pollution may be defined as the - presence of substances in the atmosphere, resulting from man- made activities or from natural processes, causing adverse effects to man and the environment.
POP
Probability of Precipitation. Probability forecasts are subjective estimates of the chances of encountering measurable precipitation at some time during the forecast period.
Popcorn Convection
Clouds, showers and thundershowers that form on a scattered basis with little or no apparent organization, usually during the afternoon in response to diurnal heating.
Positive Area
The area on a sounding representing the layer in which a lifted parcel would be warmer than the environment; thus, the area between the environmental temperature profile and the path of the lifted parcel.
Positive- tilt Trough
An upper level system which is tilted to the east with increasing latitude (i.e., from southwest to northeast). A positive- tilt trough often is a sign of a weakening weather system, and generally is less likely to result in severe weather than a negative- tilt trough if all other factors are equal.
Potential Temperature
The 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.
Precipitation Shaft
A visible column of rain and/or hail falling from a cloud base. When viewed against a light background, heavy precipitation appears very dark gray, sometimes with a turquoise tinge. This turquoise tinge has been commonly attributed to hail, but its actual cause is unknown.
Pressure
The force exerted by the interaction of the atmosphere and gravity. Also known as atmospheric pressure.
Pressure Change
The net difference between pressure readings at the beginning and ending of a specified interval of time.
Pressure Falling Rapidly
A 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 Gradient Force
Force acting on air that causes it to move from areas of higher pressure to areas of lower pressure.
Pressure Rising Rapidly
An 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 Tendency.
The character and amount of atmospheric pressure change during a specified period of time, usually the 3 - hour period preceding an observation.
Pressure Unsteady
A pressure that fluctuates by 0.03 inch of mercury or more from the mean pressure during the period of measurement.
Prevailing Westerlies
Winds in the middle latitudes (approximately 30 degrees to 60 degrees) that generally blow from west to east.
Profiler
An instrument designed to measure horizontal winds directly above its location, and thus measure the vertical wind profile. Profilers operate on the same principles as Doppler radar.
Pulse Storm
A thunderstorm within which a brief period (pulse) of strong updraft occurs, during and immediately after which the storm produces a short episode of severe weather. These storms generally are not tornado producers, but often produce large hail and/or damaging winds. See overshooting top, cyclic storm.