A
Advisory
Statements
that are issued by the National Weather Service for probable weather situations
of inconvenience that do not carry the danger of warning criteria, but, if not
observed, could lead to hazardous situations. Some examples include snow
advisories stating possible slick streets, or fog advisories for patchy fog
condition causing temporary restrictions to visibility
Air
This is
considered the mixture of gases that make up the earth's atmosphere. The
principal gases that compose dry air are Nitrogen, Oxygen, Argon, and Carbon Dioxide. One of
the most important constituents of air and most important gases in meteorology is water vapor.
Air Mass
An extensive
body of air throughout which the horizontal temperature and moisture
characteristics are similar.
Air Mass
Thunderstorm
A thunderstorm that is
produced by convection
within an unstable air
mass through an instability
mechanism. Such thunderstorms normally occur within a tropical or warm,
moist air mass during the summer afternoon as the result of afternoon heating
and dissipate soon after sunset.
Such thunderstorms are not generally associated with fronts and are less
likely to become severe
than other types of thunderstorms. However, that does not preclude them from
having brief heavy downpours.
Air
Pollution
The soiling
of the atmosphere by
contaminants to the point that may cause injury to health, property, plant, or
animal life, or prevent the use and enjoyment of the outdoors.
Altitude
Height
Height
Anemometer
An
instrument that measures the speed or force of the wind.
Artic Air
Mass
An air mass that develops
around the Arctic,
it is characterized by being cold from surface to great heights. The boundary
of this air mass is often defined by the Arctic front, a
semi-permanent, semi-continuous feature. When this air mass moves from its
source region, it may become more shallow in height as it spreads southward.
Arid
A term used for an extremely dry climate. The
degree to which a climate lacks effective, life-promoting moisture. It is
considered the opposite of humid when speaking of climates.
Atmosphere
The gaseous
or air portion of the physical environment that encircles a planet. In the case
of the earth, it is held more or less near the surface by the earth's
gravitational attraction. The divisions of the atmosphere include the
troposphere, the stratosphere, the mesosphere, the ionosphere, and the
exosphere.
Atmpspheric
Pressure
The pressure exerted by
the atmosphere at a
given point. Its measurement can be expressed in several ways. One is in millibars.
Aurora
It is
created by the radiant energy emission from the sun and its interaction with
the earth's upper atmosphere over the middle and high latitudes. It is seen as
a bright display of constantly changing light near the magnetic poles of each
hemisphere. In the Northern Hemisphere, it is known as the aurora borealis or
Northern Lights, and in the Southern Hemisphere, this phenomena is called the
aurora australis.
Autumn
(Fall)
The season of the year which occurs as the
sun approaches the winter
solstice, and
characterized by decreasing temperatures in the mid-latitudes.
Customarily, this refers to the months of September, October, and November in
the North Hemisphere and the months of March, April, and May in the Southern
Hemisphere. Astronomically, this is the period between the autumnal equinox and the
winter solstice.
B
B
Black
Blizzard
A local term
for a violent duststorm
on the south-central Great Plains that darkens the sky and casts a pall over
the land.
Black Ice
Thin, new ice on fresh or salt water that
appears dark in color because of its transparency.
Also refers to thin, transparent ice on road surfaces.
Blizzard
A severe weather condition
characterized by low temperatures,
winds 35 mph or
greater, and sufficient falling and/or blowing snow in the air
to frequently reduce visibility
to 1/4 mile or less for a duration of at least 3 hours. A severe blizzard is
characterized by temperatures near or below 10°F, winds exceeding 45 mph, and
visibility reduced by snow to near zero.
Blocking
High
The
development of a warm ridge
or cutoff high aloft
at high latitudes
which becomes associated with a cold high at the
surface, causing a split in the westerly winds. Such a
high will move very slowly, tending to move westward during intensification and
eastward during dissipation. It prevents the movement of migratory cyclones across its
latitudes, Known to cause droughts
Blowing Dust
Dust that is raised by
the wind to heights
of six feet or greater.
Blowing Sand
Sand that is
raised by the wind to heights of six feet or greater
Blowing Snow
Snow that is raised by
the wind to heights
of six feet or greater.
Bubble High
A small high that may be created
by precipitation
and vertical instability
associated with thunderstorm
activity. A product of downdrafts,
it is relatively cold
and often has the characteristics of a different air mass. Convergence along
the leading edge of a bubble high may help form additional thunderstorms
C
Calm
Atmospheric conditions
devoid of wind or any
other air motion. In oceanic terms, it is the apparent absence of motion of the
water surface when there is no wind or swell.
Celing
The lowest cloud layer that is
reported as broken or overcast. If the sky is
totally obscured, then
it is the height of the vertical visibility.
Clear
The state of
the sky when no clouds or obscurations are observed
or detected from the point of observation.
Clear Ice
A glossy,
clear, or translucent
ice formed by the
relatively slow freezing
of large supercooled
in water droplets.
The droplets spread out over an object, such as an aircraft wing's leading
edge, prior to complete freezing and forms a sheet of clear ice
Climate
The
historical record and description of average daily and in seasonal weather events that help
describe a region. Statistics are generally drawn over several decades. The
word is derived from the Greek klima, meaning inclination, and reflects the
importance early scholars attributed to the sun's influence
Climatology
The study of
climate. It
includes climatic data, the analysis of the causes of the differences in
climate, and the application of climatic data to the solution of specific
design or operational problems/
Climatologist
A person who
studies the climate
Cloud
A visible
collection of minute particle matter, such as water droplets and/or ice crystals, in the
free air. A cloud
forms in the atmosphere
as a result of condensation
of water vapor. Condensation nuclei,
such as in smoke or dust particles, form a
surface upon which water vapor can condense.
Cloud Burst
A sudden, heavy rainfall of a showery nature.
Cold
A condition marked by low or decidedly subnormal temperature. The lack of
heat.
Cold Core Thunderstorms
Thunderstorms
formed primarily due to steep lapse rates, especially
when very cold air
aloft overlies warmer
surface air.
Cold Front
The leading edge of an advancing cold air mass that is
under running and displacing the warmer air in its path. Generally, with the
passage of a cold front, the temperature and humidity decrease, the pressure rises, and
the wind shifts
(usually from the southwest to the northwest in the Northern Hemisphere). Precipitation is
generally at and/or behind the front, and with a
fast-moving system, a squall
line may develop ahead of the front.
Cold High
A high pressure
system that has its coldest temperatures at or near
the center of circulation,
and horizontally, is thermally barotropic. It is
shallow in nature, as circulation decreases with height. Associated with cold Arctic air, it is
usually stationary.
Cold Low
A low pressure
system that has its coldest temperatures at or near
the center of circulation,
and is thermally barotropic
with respect to a horizontal plane. Also known as a cold core low. A cut off low is an
example, where an isolated pool of colder air is located south of the main westerlies.
Condensation
The process
by which water vapor undergoes a change in state from a gas to a liquid. It is
the opposite physical process of evaporation.
Current
A horizontal movement of water, such as the Gulf Stream
off the east coast of North America, or air, such as the jet stream.
A warm high
which has become displaced and is on the polarward
side of the jet stream. It occurs mostly during the spring
and is most frequent over northeastern Siberia, Alaska, and Greenland. It is an
example of a blocking high.
A
closed cold core low completely removed from the primary westerly flow.
Cutoff lows may remain detached from the westerlies for days while exhibiting
very little forward (eastward) progress. In some instances, a cutoff low may
move to the west, or retrograde, opposite to the prevailing flow. It is important
to note that a cutoff low is a closed low, but not all closed lows are cutoff
lows.
Cyclone
An area of closed pressure circulation with rotating and converging winds,
the center of which is a relative pressure minimum. The circulation is
counterclockwise in the Northern Hemisphere and clockwise in the Southern
Hemisphere. Also called a low pressure system and the term used for a tropical
cyclone in the Indian Ocean. Other phenomena with cyclonic flow may be referred
to by this term, such as dust devils, tornadoes, and tropical and extratropical
systems. The opposite of an anticyclone or a high pressure system.
D
Daily Mean
The average temperature for a day computed by averaging either the
hourly readings or, more commonly, the maximum and minimum temperatures.
Dawn
The
first appearance of light in the eastern sky before sunrise.
It marks the beginning of morning twilight.
The visual display is created by the scattering of light reaching the upper atmosphere
prior to the sun's rise to the observer's horizon.
Day
Considered a basic unit of time as defined by the earth's motion. It
represents the time needed for one complete revolution of the earth about its
own axis. Also known as a sidereal day, it is approximately equal to 23 hours,
56 minutes, and 4.09 seconds.
Debris Cloud
Considered a rotating cloud of debris or dust that is on the ground or
near the ground. The debris cloud appearing beneath a thunderstorm will most
likely confirm the presence of a tornado.
Degree
A measure of temperature difference representing a single division on a
temperature scale.
Depression
In meteorology, it is another name for an area of low pressure, a low,
or trough. It also applies to a stage of tropical cyclone development and is
known as a tropical depression to distinguish it from other synoptic features.
Dew
Condensation in the form of small water drops that forms on grass and
other small objects near the ground when the temperature has fallen to the dew
point, generally during the nighttime hours.
Dew Point
The temperature to which air must be cooled at a constant pressure to
become saturated.
Doppler Radar
Weather radar that measures direction and speed of a moving object,
such as drops of precipitation, by determining whether atmospheric motion is horizontally
toward or away from the radar. Using the Doppler effect, it measures the
velocity of particles. Named for J. Christian Doppler, an Austrian physicist,
who in 1842 explained why the whistle of an approaching train had a higher
pitch than the same whistle when the train was going away.
Downburst
A severe localized downdraft from a
thunderstorm or shower. This outward burst of cool or colder air creates
damaging winds at or near the surface. Sometimes the damage resembles tornadic
damage.
Downdraft
A sudden descent of cool or cold air to the ground, usually with precipitation,
and associated with a thunderstorm or shower.
Downpour
Heavy rain
Drifting Snow
Snow particles blown from the ground by the wind to a height of less
than six feet.
Drizzle
Slowly falling precipitation in the form of tiny water droplets with
diameters less than 0.02 inches or 0.5 millimeters. It falls from stratus
clouds and is often associated with low visibility and fog.
Drought
Abnormal dry weather for a specific area that is sufficiently prolonged
for the lack of water to cause serious hydrological imbalance.
Dusk
The period of waning light from the time of sunset to dark.
Dust
Small particles of earth or other
matter suspended in the air.
Dust Bowl
The term given to the area of the Great Plains including Texas,
Oklahoma, Kansas, Colorado, and New Mexico that was most greatly affected
during the Great Drought of the 1930'sThe term given to the area of the Great
Plains including Texas, Oklahoma, Kansas, Colorado, and New Mexico that was
most greatly affected during the Great Drought of the 1930's.
Dust Devil
A small, rapidly rotating column of
wind, made visible by the dust, dirt or debris it picks up. It usually occurs
in arid or semi-arid areas and is most likely to develop on clear, dry, hot
afternoons in response to surface heating.
Dust Storm
A severe weather condition characterized by
strong winds and dust-filled air over a large area. Visibility is reduced to
between 5/8ths and 5/16ths statute mil
No comments:
Post a Comment