Subj : Weather Terms (C) Part 1
To   : All
From : Daryl Stout
Date : Tue Oct 04 2016 12:07 am

C
1. Degrees Celsius (?C)

2. Central

C AMS
Continental Air Mass

CA
Cloud-to-Air lightning.

CAA
Cold Air Advection

CAD
Cold Air Damming. The phenomenon in which a low-level cold air mass is
trapped topographically. Often, this cold air is entrenched on the east
side of mountainous terrain. Cold Air Damming often implies that the
trapped cold air mass is influencing the dynamics of the overlying air
mass, e.g. in an overrunning scenario. Effects on the weather may include
cold temperatures, freezing precipitation, and extensive cloud cover.

CADAS
Centralized Automated Data Acquisition System - a system of two
minicomputers in NWSH.

Calibration
In hydrologic terms, the process of using historical data to estimate
parameters in a hydrologic forecast technique such as SACSMA, routings,
and unit hydrographs.

Calm
A weather condition when no air motion (wind) is detected.

Canyon Wind
A foehn wind that is channeled through a canyon as it descends the lee
side of a mountain barrier.

Cap
(also called "Lid") A layer of relatively warm air aloft, usually several
thousand feet above the ground, which suppresses or delays the development
of thunderstorms. Air parcels rising into this layer become cooler than
the surrounding air, which inhibits their ability to rise further and
produce thunderstorms. As such, the cap often prevents or delays
thunderstorm development even in the presence of extreme instability.
However, if the cap is removed or weakened, then explosive thunderstorm
development can occur.

The cap is an important ingredient in most severe thunderstorm episodes,
as it serves to separate warm, moist air below and cooler, drier air
above. With the cap in place, air below it can continue to warm and/or
moisten, thus increasing the amount of potential instability. Or, air
above it can cool, which also increases potential instability. But
without a cap, either process (warming/moistening at low levels or
cooling aloft) results in a faster release of available instability -
often before instability levels become large enough to support severe
weather development.

Cap Cloud
A stationary cloud directly above an isolated mountain peak, with cloud
base below the elevation of the peak.

CAPE
Convective Available Potential Energy. A measure of the amount of energy
available for convection. CAPE is directly related to the maximum
potential vertical speed within an updraft; thus, higher values indicate
greater potential for severe weather. Observed values in thunderstorm
environments often may exceed 1000 joules per kilogram (J/kg), and in
extreme cases may exceed 5000 J/kg.

However, as with other indices or indicators, there are no threshold
values above which severe weather becomes imminent. CAPE is represented
on an upper air sounding by the area enclosed between the environmental
temperature profile and the path of a rising air parcel, over the layer
within which the latter is warmer than the former. (This area often is
called positive area.) See also CIN.

Capillarity
In hydrologic terms,

1.The degree to which a material or object containing minute openings or
passages, when immersed in a liquid, will draw the surface of the liquid
above the hydrostatic level. Unless otherwise defined, the liquid is
generally assumed to be water.

2. The phenomenon by which water is held in interstices above the normal
hydrostatic level, due to attraction between water molecules.

Capillary Fringe
In hydrologic terms, the soil area just above the water table where water
can rise up slightly through the cohesive force of capillary action. This
layer ranges in depth from a couple of inches, to a few feet, and it
depends on the pore sizes of the materials. The capillary fringe is also
called the capillary zone.

Capillary Waves
Waves caused by the initial wind stress on the water surface causes what
are known as capillary waves. These have a wavelength of less than 1.73
cm, and the force that tries to restore them to equilibrium is the
cohesion of the individual molecules. Capillary waves are important in
starting the process of energy transfer from the air to the water.

Capillary Zone
Used interchangably with Capillary Fringe; the soil area just above the
water table where water can rise up slightly through the cohesive force
of capillary action. This layer ranges in depth from a couple of inches,
to a few feet, and it depends on the pore sizes of the materials.

Capping
A region of negative buoyancy below an existing level of free convection
(LFC) where energy must be supplied to the parcel to maintain its ascent.
This tends to inhibit the development of convection until some physical
mechanism can lift a parcel to its LFC. The intensity of the cap is
measured by its convective inhibition. The term capping inversion is
sometimes used, but an inversion is not necessary for the conditions
producing convective inhibition to exist.

Capping Inversion
Alternate term for Cap; a layer of relatively warm air aloft, usually
several thousand feet above the ground, which suppresses or delays the
development of thunderstorms. Air parcels rising into this layer become
cooler than the surrounding air, which inhibits their ability to rise
further and produce thunderstorms. As such, the cap often prevents or
delays thunderstorm development even in the presence of extreme
instability. However, if the cap is removed or weakened, then explosive
thunderstorm development can occur.

The cap is an important ingredient in most severe thunderstorm episodes,
as it serves to separate warm, moist air below and cooler, drier air
above. With the cap in place, air below it can continue to warm and/or
moisten, thus increasing the amount of potential instability. Or, air
above it can cool, which also increases potential instability. But
without a cap, either process (warming/moistening at low levels or
cooling aloft) results in a faster release of available instability -
often before instability levels become large enough to support severe
weather development.

CAPS
Center for Analysis and Prediction of Storms

Carbon Dioxide
CO2; a colorless and odorless gas which is the fourth most abundant
constituent of dry air.

Carrington Longitude
A system of fixed longitudes rotating with the sun.

Catalina Eddy
A Catalina Eddy (coastal eddy) forms when upper level large-scale flow
off Point Conception interacts with the complex topography of the
Southern California coastline. As a result, a counter clockwise
circulating low pressure area forms with its center in the vicinity of
Catalina Island. This formation is accompanied by a southerly shift in
coastal winds, a rapid increase in the depth of the marine layer, and a
thickening of the coastal stratus. Predominately these eddies occur
between April and September with a peak in June. A typical Catalina
eddy will allow coastal low clouds and fog to persist into the
afternoon. A strong Catalina eddy may extend to 6000 feet and these
clouds will move through the inland valleys and reach as far as
Palmdale.

Catchment Area
In hydrologic terms, an area having a common outlet for its surface
runoff (also see Drainage Area or Basin, Watershed).

Categorical
A National Weather Service precipitation descriptor for a 80, 90, or
100 percent chance of measurable precipitation (0.01 inch). See
Precipitation Probability (PoP)

CAVU
Clear or Scattered Clouds (visibility greater than 10 mi.)

Cb
Cumulonimbus cloud, characterized by strong vertical development in
the form of mountains or huge towers topped at least partially by a
smooth, flat, often fibrous anvil. Also known colloquially as a
"thunderhead."

CBMAM
Cumulonimbus Mamma

CC
Cloud-to-Cloud Lightning

CCITT
Consultative Committee for International Telephone and Telegraph


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