Subj : Weather Terms (C) Part 6
To   : All
From : Daryl Stout
Date : Tue Oct 04 2016 12:08 am

Convergence
A contraction of a vector field; the opposite of divergence. Convergence
in a horizontal wind field indicates that more air is entering a given
area than is leaving at that level. To compensate for the resulting
"excess," vertical motion may result: upward forcing if convergence is
at low levels, or downward forcing (subsidence) if convergence is at
high levels. Upward forcing from low-level convergence increases the
potential for thunderstorm development (when other factors, such as
instability, are favorable). Compare with confluence.

Conveyance Loss
In hydrologic terms, the loss of water from a conduit due to leakage,
seepage, evaporation, or evapo-transpiration.

Cooling Degree Days
(Abbrev. CDD) - A form of Degree Day used to estimate energy requirements
for air conditioning or refrigeration. Typically, cooling degree days are
calculated as how much warmer the mean temperature at a location is than
65� F on a given day. For example, if a location experiences a
mean temperature of 75� F on a certain day, there were 10 CDD
(Cooling Degree Days) that day because 75 - 65 = 10.

Cooperative Observer
An individual (or institution) who takes precipitation and temperature
observations-and in some cases other observations such as river stage,
soil temperature, and evaporation-at or near their home, or place of
business. Many observers transmit their reports by touch-tone telephone
to an NWS computer, and nearly all observers mail monthly reports to
the National Climatic Data Center to be archived and published.

Coordinated Universal Time (UTC)
By international agreement, the local time at the prime meridian, which
passes through Greenwich, England. Prior to 1972, this time was called
Greenwich Mean Time (GMT) but is now referred to as Coordinated
Universal Time or Universal Time Coordinated (UTC). It is a coordinated
time scale, maintained by the Bureau International des Poids et Mesures
(BIPM). It is also known a "Z time" or "Zulu Time".

More about UTC, and a table to convert UTC to your local time is posted
at: http://www.srh.noaa.gov/jetstream/remote/radarfaq.htm#utc

COR
Correction

Core Punch
[Slang], a penetration by a vehicle into the heavy precipitation core of
a thunderstorm. Core punching is not a recommended procedure for storm
spotting.

Coriolis Force
A fictitious force used to account for the apparent deflection of a body
in motion with respect to the earth, as seen by an observer on the earth.
The deflection (to the right in the Northern Hemisphere) is caused by the
rotation of the earth.

Corn Snow Ice
In hydrologic terms, rotten granular ice.

Corner Effects
A small-scale convergence effect that can be quite severe. It occurs
around steep islands and headlands.

Corona
1. The outermost layer of the solar atmosphere, characterized by low
densities (< 1.0x109/cc) and high temperatures (> 1.0x106 K).

2. In solar-terrestrial terms, a white or colored circle or set of
concentric circles of light of small radius seen around a luminous body,
especially around the sun or moon. The color varies from blue inside to
red outside and the phenomenon is attributed to diffraction of light by
thin clouds or mist (distinguished from halo).

Coronal Hole
In solar-terrestrial terms, an extended region of the corona,
exceptionally low in density and associated with unipolar photospheric
regions.

Coronal Rain
(Abbrev. CRN) In solar-terrestrial terms, material condensing in the
corona and appearing to rain down into the chromosphere as observed at
the solar limb above strong sunspots.

Coronal Transients
In solar-terrestrial terms, a general term for short-time-scale changes
in the corona, but principally used to describe outward-moving plasma
clouds.

Cosmic Ray
An extremely energetic (relativistic) charged particle.

County Warning and Forecast Area
The group of counties for which a National Weather Service Forecast
Office is responsible for issuing warnings and weather forecasts.

County Warning Area
The group of counties for which a National Weather Service Forecast
Office is responsible for issuing warnings.

Coupled Atmosphere-Ocean Model
Same as Coupled Model; in the context of climate modeling this usually
refers to a numerical model which simulates both atmospheric and oceanic
motions and temperatures and which takes into account the effects of
each component on the other.

Coupled Model
In the context of climate modeling this usually refers to a numerical
model which simulates both atmospheric and oceanic motions and
temperatures and which takes into account the effects of each component
on the other.

CPC
Climate Prediction Center

Creek
A small stream of water which serves as the natural drainage course for
a drainage basin of nominal, or small size. The term is a relative one
as to size, some creeks in the humid section would be called rivers if
they occurred in the arid portion.

Crepuscular Rays
The alternating bands of light and dark (rays and shadows) seen at the
earth's surface when the sun shines through clouds.

Crest
Highest point in a wave.

In hydrologic terms,
(1) The highest stage or level of a flood wave as it passes a point.
(2) The top of a dam, dike, spillway, or weir, to which water must rise
before passing over the structure.

Crest Gage
A gage used to obtain a record of flood crests at sites where recording
gages are installed.

Crest Width
In hydrologic terms, the thickness or width of a dam at the level of the
crest (top) of the dam. The term "thickness" is used for gravity and
arch dams and "width" for other types of dams.

Critical Depth
In hydrologic terms, The depth of water flowing in an open channel or
conduit, partially filled, corresponding to one of the recognized
critical velocities.

Critical Flow
In hydrologic terms, a condition of flow where the mean velocity is at
one of the critical values; ordinarily at Belanger's critical depth and
velocity. Another important usage is in reference to the Reynolds'
critical velocities which define the point at which the flow changes
from streamline or nonturbulent to turbulent flow.

Critical Rainfall Probability
(Abbrev. CRP) - In hydrologic terms, the Probability that the actual
precipitation during a rainfall event has exceeded or will exceed the
flash flood guidance value.

CRN
Coronal Rain - In solar-terrestrial terms, material condensing in the
corona and appearing to rain down into the chromosphere as observed at
the solar limb above strong sunspots.

Crochet
In solar-terrestrial terms, a sudden deviation in the sunlit geomagnetic
field (H component; see geomagnetic elements) associated with large
solar flare X-ray emission.

Crop Moisture Index
In 1968, Palmer developed the index to assess short-term crop water
conditions and needs across major crop-producing regions. This index
is a useful tool in forecasting short-term drought conditions.

Cross-Valley Wind System
A thermally driven wind that blows during daytime across the axis of a
valley toward the heated sidewall.

Crown Fire
A fire where flames travel from tree to tree at the level of the tree's
crown or top.

Crowning
Movement of a fire from the understory into the crown of a forest canopy.

CRP
Critical Rainfall Probability - in hydrologic terms, the probability that
a given rainfall will cause a river, or stream to rise above flood stage.

CRS
Console Replacement System for NOAA Weather Radio.


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