There are 60 names in this directory beginning with the letter C.
Cap (or Capping Inversion)
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. As such, the cap often prevents or delays thunderstorm development even in the presence of extreme instability.
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 1,000 joules per kilogram (j/kg), and in extreme cases may exceed 5,000 j/kg. However, as with other indices or indicators, there are no threshold values above which severe weather becomes imminent.
Ceilometer
A device used to evaluate the height of clouds or the vertical visibility into a surface-based obscuration.
Cell
Convection in the form of a single updraft, downdraft, or updraft/downdraft couplet, typically seen as a vertical dome or tower as in a cumulus or towering cumulus cloud. A typical thunderstorm consists of several cells
Celsius
A temperature scale in which zero is the freezing point of water and one hundred is the boiling point.
Chinook Wind
A strong downslope wind that causes the air to warm rapidly as a result of compressive heating; called a foehn wind in Europe.
Circulation
The pattern of the movement of air. General circulation is the flow of air of large, semi-permanent weather systems, while secondary circulation is the flow of air of more temporary weather systems
Cirrus
High clouds, usually above 18,000 feet, composed of ice crystals and appearing in the form of white, delicate filaments or white or mostly white patches or narrow bands.
Clear Slot
A local region of clearing skies or reduced cloud cover, indicating an intrusion of drier air; often seen as a bright area with higher cloud bases on the west or southwest side of a wall cloud.
Climate
The prevalent long term weather conditions in a particular area. Climatic elements include precipitation, temperature, humidity, sunshine and wind
Closed Low
A low pressure area with a distinct center of cyclonic circulation which can be completely encircled by one or more isobars or height contour lines. The term usually is used to distinguish a low pressure area aloft from a low-pressure trough. Closed lows aloft typically are partially or completely detached from the main westerly current, and thus move relatively slowly.
Cloud Base
For a given cloud or cloud layer, it is the lowest level in the atmosphere where cloud particles are visible.
Cloud Condensation Nuclei
Small particles in the air on which water vapor condenses and forms cloud droplets.
Cloud Streets
Rows of cumulus or cumulus-type clouds aligned parallel to the low-level flow. Cloud streets sometimes can be seen from the ground, but are seen best on satellite photographs.
Coastal Flood Warning
Issued when there is widespread coastal flooding expected within 12 hours, more than just typical overwash.
Coastal Forecast
A forecast of wind, wave and weather conditions between the coastline and 25 miles offshore.
Coastal Waters
Include the area from a line approximating the mean high water along the mainland or island as far out as 25 miles including the bays, harbors and sounds.
Cold Front
A narrow transition zone separating advancing colder air from retreating warmer air. The air behind a cold front is cooler and typically drier than the air it is replacing.
Cold Low
A low pressure system with cold air mass from near the surface to all vertical levels (also called a cold core low).
Cold Pool
A region of relatively cold air, represented on a weather map analysis as a relative minimum in temperature surrounded by closed isotherms. Cold pools aloft represent regions of relatively low stability, while surface-based cold pools are regions of relatively stable air.
Cold-air Funnel
A funnel cloud or (rarely) a small, relatively weak tornado that can develop from a small shower or thunderstorm when the air aloft is unusually cold (hence the name). They are much less violent than other types of tornadoes.
Collar Cloud
Frequently used as a synonym for wall cloud, although it actually is a generally circular ring of cloud surrounding the upper portion of a wall cloud.
Comma Cloud
A synoptic scale cloud pattern with a characteristic comma-like shape, often seen on satellite photographs associated with large and intense low-pressure systems.
Condensation
The process by which water vapor becomes a liquid; the opposite of evaporation, which is the conversion of liquid to vapor.
Confluence
A pattern of wind flow in which air flows inward toward an axis oriented parallel to the general direction of flow. It is the opposite of difluence. Confluence is not the same as convergence. Winds often accelerate as they enter a confluent zone, resulting in speed divergence which offsets the (apparent) converging effect of the confluent flow.
Congestus (or Cumulus Congestus)
A large cumulus cloud with great vertical development, usually with a cauliflower-like appearance, but lacking the characteristic anvil shaped top of a Cb.
Convective Outlook
A forecast containing the area(s) of expected thunderstorm occurrence and expected severity over the contiguous United States, issued several times daily by the SPC.
Convective Temperature
The approximate temperature that the air near the ground must warm to in order for surface - based convection to develop, based on analysis of a sounding.
Convergence
An atmospheric condition that exists when the winds cause a horizontal net inflow of air into a specified region. Divergence is the opposite, where winds cause a horizontal net outflow of air from a specified region.
Cooling Degree Day
A form of degree day used to estimate the required energy for cooling. one cooling degree day occurs for each degree the daily mean temperature is above 65 degrees Fahrenheit.
Coriolis Force
An apparent force caused by the rotation of the Earth. In the Northern Hemisphere winds are deflected to the right, and in the Southern Hemisphere to the left. In synoptic scale weather systems (hurricanes and large mid-latitude storms), the Coriolis force causes the air to rotate around a low pressure center in a cyclonic direction. The air flowing around a hurricane spins counter-clockwise in the northern hemisphere
Corona
A disk of light surrounding the sun or moon; this is a result of the diffraction of light by small water droplets.
Cumulonimbus Cloud
A vertically developed cloud, often capped by an anvil shaped cloud. Also called a thunderstorm cloud, it is frequently accompanied by heavy showers, lightning, thunder, and sometimes hail or gusty winds.
Cumulus Cloud
A cloud in the shape of individual detached domes, with a flat base and a bulging upper portion resembling cauliflower.
Cumulus Congestus
A large cumulus cloud with great vertical development, usually with a cauliflower- like appearance, but lacking the characteristic anvil shaped top of a Cb.
Cut Off Low
An upper level low pressure system that is no longer in the normal west to east upper air flow. Usually a cut- off low will lie to the South of the established upper air flow.
Cyclone
An area of low pressure around which winds blow counterclockwise in the Northern Hemisphere. Also the term used for a hurricane in the Indian Ocean and in the Western Pacific Ocean.
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Cap (or Capping Inversion)
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. As such, the cap often prevents or delays thunderstorm development even in the presence of extreme instability.
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 1,000 joules per kilogram (j/kg), and in extreme cases may exceed 5,000 j/kg. However, as with other indices or indicators, there are no threshold values above which severe weather becomes imminent.
Ceilometer
A device used to evaluate the height of clouds or the vertical visibility into a surface-based obscuration.
Cell
Convection in the form of a single updraft, downdraft, or updraft/downdraft couplet, typically seen as a vertical dome or tower as in a cumulus or towering cumulus cloud. A typical thunderstorm consists of several cells
Celsius
A temperature scale in which zero is the freezing point of water and one hundred is the boiling point.
Chinook Wind
A strong downslope wind that causes the air to warm rapidly as a result of compressive heating; called a foehn wind in Europe.
Circulation
The pattern of the movement of air. General circulation is the flow of air of large, semi-permanent weather systems, while secondary circulation is the flow of air of more temporary weather systems
Cirrus
High clouds, usually above 18,000 feet, composed of ice crystals and appearing in the form of white, delicate filaments or white or mostly white patches or narrow bands.
Clear Slot
A local region of clearing skies or reduced cloud cover, indicating an intrusion of drier air; often seen as a bright area with higher cloud bases on the west or southwest side of a wall cloud.
Climate
The prevalent long term weather conditions in a particular area. Climatic elements include precipitation, temperature, humidity, sunshine and wind
Closed Low
A low pressure area with a distinct center of cyclonic circulation which can be completely encircled by one or more isobars or height contour lines. The term usually is used to distinguish a low pressure area aloft from a low-pressure trough. Closed lows aloft typically are partially or completely detached from the main westerly current, and thus move relatively slowly.
Cloud Base
For a given cloud or cloud layer, it is the lowest level in the atmosphere where cloud particles are visible.
Cloud Condensation Nuclei
Small particles in the air on which water vapor condenses and forms cloud droplets.
Cloud Streets
Rows of cumulus or cumulus-type clouds aligned parallel to the low-level flow. Cloud streets sometimes can be seen from the ground, but are seen best on satellite photographs.
Coastal Flood Warning
Issued when there is widespread coastal flooding expected within 12 hours, more than just typical overwash.
Coastal Forecast
A forecast of wind, wave and weather conditions between the coastline and 25 miles offshore.
Coastal Waters
Include the area from a line approximating the mean high water along the mainland or island as far out as 25 miles including the bays, harbors and sounds.
Cold Front
A narrow transition zone separating advancing colder air from retreating warmer air. The air behind a cold front is cooler and typically drier than the air it is replacing.
Cold Low
A low pressure system with cold air mass from near the surface to all vertical levels (also called a cold core low).
Cold Pool
A region of relatively cold air, represented on a weather map analysis as a relative minimum in temperature surrounded by closed isotherms. Cold pools aloft represent regions of relatively low stability, while surface-based cold pools are regions of relatively stable air.
Cold-air Funnel
A funnel cloud or (rarely) a small, relatively weak tornado that can develop from a small shower or thunderstorm when the air aloft is unusually cold (hence the name). They are much less violent than other types of tornadoes.
Collar Cloud
Frequently used as a synonym for wall cloud, although it actually is a generally circular ring of cloud surrounding the upper portion of a wall cloud.
Comma Cloud
A synoptic scale cloud pattern with a characteristic comma-like shape, often seen on satellite photographs associated with large and intense low-pressure systems.
Condensation
The process by which water vapor becomes a liquid; the opposite of evaporation, which is the conversion of liquid to vapor.
Confluence
A pattern of wind flow in which air flows inward toward an axis oriented parallel to the general direction of flow. It is the opposite of difluence. Confluence is not the same as convergence. Winds often accelerate as they enter a confluent zone, resulting in speed divergence which offsets the (apparent) converging effect of the confluent flow.
Congestus (or Cumulus Congestus)
A large cumulus cloud with great vertical development, usually with a cauliflower-like appearance, but lacking the characteristic anvil shaped top of a Cb.
Convective Outlook
A forecast containing the area(s) of expected thunderstorm occurrence and expected severity over the contiguous United States, issued several times daily by the SPC.
Convective Temperature
The approximate temperature that the air near the ground must warm to in order for surface - based convection to develop, based on analysis of a sounding.
Convergence
An atmospheric condition that exists when the winds cause a horizontal net inflow of air into a specified region. Divergence is the opposite, where winds cause a horizontal net outflow of air from a specified region.
Cooling Degree Day
A form of degree day used to estimate the required energy for cooling. one cooling degree day occurs for each degree the daily mean temperature is above 65 degrees Fahrenheit.
Coriolis Force
An apparent force caused by the rotation of the Earth. In the Northern Hemisphere winds are deflected to the right, and in the Southern Hemisphere to the left. In synoptic scale weather systems (hurricanes and large mid-latitude storms), the Coriolis force causes the air to rotate around a low pressure center in a cyclonic direction. The air flowing around a hurricane spins counter-clockwise in the northern hemisphere
Corona
A disk of light surrounding the sun or moon; this is a result of the diffraction of light by small water droplets.
Cumulonimbus Cloud
A vertically developed cloud, often capped by an anvil shaped cloud. Also called a thunderstorm cloud, it is frequently accompanied by heavy showers, lightning, thunder, and sometimes hail or gusty winds.
Cumulus Cloud
A cloud in the shape of individual detached domes, with a flat base and a bulging upper portion resembling cauliflower.
Cumulus Congestus
A large cumulus cloud with great vertical development, usually with a cauliflower- like appearance, but lacking the characteristic anvil shaped top of a Cb.
Cut Off Low
An upper level low pressure system that is no longer in the normal west to east upper air flow. Usually a cut- off low will lie to the South of the established upper air flow.
Cyclone
An area of low pressure around which winds blow counterclockwise in the Northern Hemisphere. Also the term used for a hurricane in the Indian Ocean and in the Western Pacific Ocean.