Subj : Wx Terms (P)(5)
To : All
From : Daryl Stout
Date : Thu Aug 17 2017 12:04 am
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 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.
Pressure-driven Channeling
Channeling of wind in a valley by synoptic-scale pressure gradients
superimposed along the valley's axis. Compare forced channeling.
Prevailing Visibility
The visibility that is considered representative of conditions at the
station; the greatest distance that can be seen throughout at least
half the horizon circle, not necessarily continuous.
Prevailing Westerlies
The westerly winds that dominant in middle latitudes.
Prevailing Winds
A wind that consistently blows from one direction more than from any
other.
Prevention of Significant Deterioration
A program, specified in the Clean Air Act, whose goal is to prevent air
quality from deteriorating significantly in areas of the country that
are presently meeting the ambient air quality standards.
PRIM
Primary
Primary Ambient Air Quality Standards
Air quality standards designed to protect human health.
Primary Control Tide Station
A tide station where continuous observations have been made for a
minimum of 19 years. Its purpose is to provide data for computing
accepted values essential to tide predictions and for determining
tidal datums for coastal and marine boundaries. The data series from
primary control tide stations serves as a primary control for the
reduction of tidal datum for subordinate tide stations with a shorter
period of record. The 19 year period is the official tidal epoch for
calculating tidal datums.
Primary Pollutant
Substances that are pollutants immediately on entering the atmosphere.
Compare secondary pollutant.
Primary Swell Direction
Prevailing direction of swell propagation.
PRIN
Principal
Probability
A chance, or likelihood, that a certain event might happen.
Probability Forecast
A forecast of the probability that one or more of a mutually exclusive
set of weather conditions will occur.
Probability of Hail
(Abbrev. POH) - a product from the NEXRAD hail detection algorithm that
estimates the likelihood that hail is present in a storm.
Probability of Precipitation
(Abbrev. PoP)- The probability that precipitation will be reported at a
certain location during a specified period of time.
Probability of Thunderstorms
The probability based on climatology that a thunderstorm will be reported
at that location during a specified period of time.
Probability of Tropical Cyclone Conditions
The 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.
Product Resolution
The smallest spatial increment or data element that is distinguishable in
a given Doppler radar product.
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.
PROG
Forecast (prognostication)
PROGGED
Forecasted
Prognostic Discussion
This Hydrometeorological Prediction Center (HPC) discussion may include
analysis of numerical and statistical models, meteorological
circulation patterns and trends, and confidence factors. Reference is
usually made to the manually produced 6 to 10-day Northern Hemisphere
prognoses for mean 500 millibar heights and mean 500 millibar height
anomalies. Discussions may also refer to the method of operational
ensemble predictions.
Progressive Derecho
Derecho characterized by a short curved squall line oriented nearly
perpendicular to the mean wind direction with a bulge in the general
direction of the mean flow. Downburst activity occurs along the bulging
portion of the line. This type of derecho typically occurs in the warm
season (May through August) and is most frequent in a zone extending
from eastern South Dakota to the upper Ohio Valley. The severe wind
storms typically begin during the afternoon and continue into the
evening hours. Several hours typically pass between initial convection
and the first wind damage report.
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 DISK.
PROPA
Propagation (movement)
Propagation
1. The movement of an atmospheric phenomenon. This term is frequently
applied to the motion of thunderstorms into regions favorable for their
continued development (into a maritime tropical airmass).
2. The transmission of electromagnetic energy as waves through or along
a medium.
Property Protection
Measures that are undertaken usually by property owners in order to
prevent, or reduce flood damage. Property protection measures are often
inexpensive for the community because they are implemented by or
cost-shared with property owners. In many cases the buildings'
appearance or use is unaffected, so these measurements are particularly
appropriate for historical sites and landmarks. These measures include
relocation and acquisition, flood proofing, and buying flood insurance.
Proton
Solar activity levels with at least one high energy event (Class X
Flares).
Proton Event
In solar-terrestrial terms, the measurement of at least 10
protons/cm2/sec/steradian at energies greater than 10 MeV.
Proton Flare
In solar-terrestrial terms, any flare producing significant fluxes of
greater-than-10 MeV protons in the vicinity of the earth.
PRST
Persist
PRVD
Provide
PSBL
Possible
PSBLY
possibly
Pseudo-Cold Front
A boundary between a supercell's inflow region and the rear-flank
downdraft (or RFD). It extends outward from the mesocyclone center,
usually toward the south or southwest (but occasionally bows outward
to the east or southeast in the case of an occluded mesocyclone), and
is characterized by advancing of the downdraft air toward the inflow
region. It is a particular form of gust front.
Pseudo-Warm Front
A boundary between a supercell's inflow region and the forward-flank
downdraft (or FFD). It extends outward from at or near the mesocyclone
center, usually toward the east or southeast, and normally is either
nearly stationary or moves northward or northeastward ahead of the
mesocyclone.
PSG
Passage
PST
Pacific Standard Time
Psychrometer
An instrument used to measure the water vapor content of the air; a
hygrometer consisting essentially of two similar thermometers with the
bulb of one being kept wet so that the cooling that results from
evaporation makes it register a lower temperature than the dry one and
with the difference between the readings constituting a measure of the
dryness of the atmosphere.
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