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.
Bust - [Slang], an inaccurate forecast or an unsuccessful storm chase; usually a situation in which thunderstorms or severe weather are expected, but do not occur.
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. CAPE is represented on a 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 and sounding.
Chaff - Small strips of metal foil, usually dropped in large quantities from aircraft or balloons. Chaff typically produces a radar echo which closely resembles precipitation. Chaff drops once were conducted by the military in order to confuse enemy radar, but now are conducted mainly for radar testing and calibration purposes.
Chaser - A storm chaser is defined as a person who pursues imminent or existing severe thunderstorms, for any reason, and operates independently or as part of a research effort. Chasers are generally people from all walks of life, most of whom are very knowledgeable about meteorology and forecasting.
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."
MCC - Mesoscale Convective Complex. A large MCS, generally round or oval-shaped, which normally reaches peak intensity at night. The formal definition includes specific minimum criteria for size, duration, and eccentricity (i.e., "roundness"), based on the cloud shield as seen on infrared satellite photographs:
MCCs typically form during the afternoon and evening in the form of several isolated thunderstorms, during which time the potential for severe weather is greatest. During peak intensity, the primary threat shifts toward heavy rain and flooding.
CCM - Complejo Convectivo de Mesoescala. Gran SCM, generalmente con forma redondeada u ovalada, que normalmente alcanza un pico máximo de intensidad durante la noche. La definición formal incluye criterios mínimos específicos para el tamaño, la duración y excentricidad (es decir, “rotundidad”), basados en el escudo nuboso según es visto en las fotografías de satélite:
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 (see multi-cellular thunderstorm). The term "cell" also is used to describe the radar echo returned by an individual shower or thunderstorm. Such usage, although common, is technically incorrect.
ECMWF - European justify for Medium-Range Weather Forecasting. Operational references in forecast discussions typically refer to the ECMWF's medium-range forecast model. See MRF, UKMET.
Jet Streak - A local wind speed maximum within a jet stream.
Chorro Concentrado - Máximo de viento local dentro de una corriente en chorro (jet-stream).
Low-level Jet (abbrev. LLJ) - A region of relatively strong winds in the lower part of the atmosphere. Specifically, it often refers to a southerly wind maximum in the boundary layer, common over the Plains states at night during the warm season (spring and summer).
The term also may be used to describe a narrow zone of strong winds above the boundary layer, but in this sense the more proper term would be low-level jet stream.
Chorro de Bajos Niveles (abreviado, CBN) – Región de vientos relativamente fuertes in la parte más baja de la atmósfera. Específicamente, se refiere a menudo a un máximo de viento del sur en el estrato fronterizo, común durante la noche sobre los estados de las Llanuras durante la estación cálida (primavera y verano).
El término también se usa para describir una zona estrecha de fuertes vientos sobre el estrato fronterizo, pero en este sentido el término más apropiado sería corriente en chorro de bajos niveles.
Chorros de Entrada - Chorros de aire locales, cerca del suelo, fluyendo hacia el interior de la base de un tornado.
Forward Flank Downdraft - The main region of downdraft in the forward, or leading, part of a supercell, where most of the heavy precipitation is. Compare with rear flank downdraft. See pseudo-warm front, and supercell.
Chorro Máximo (o Máximo de Velocidad, Chorro Concentrado o Jet-Streak) – Punto o área dentro de una corriente en chorro (jet-stream) de un máximo relativo de viento.
Cyclogenesis - Development or intensification of a low-pressure justify (cyclone).
Penetrating Top - Same as overshooting top.
Cima Penetrante - Lo mismo que desbordamiento nuboso.
Cyclonic Circulation (or Cyclonic Rotation) - Circulation (or rotation) which is in the same sense as the Earth's rotation, i.e., counterclockwise (in the Northern Hemisphere) as would be seen from above. Nearly all mesocyclones and strong or violent tornadoes exhibit cyclonic rotation, but some smaller vortices, such as gustnadoes, occasionally rotate anticyclonically (clockwise). Compare with anticyclonic rotation.
Cirrus - High-level clouds (16,000 feet or more), composed of ice crystals and appearing in the form of white, delicate filaments or white or mostly white patches or narrow bands. Cirrus clouds typically have a fibrous or hairlike appearance, and often are semi-transparent. Thunderstorm anvils are a form of cirrus cloud, but most cirrus clouds are not associated with thunderstorms.
Directional Shear - The component of wind shear which is due to a change in wind direction with height, e.g., southeasterly winds at the surface and southwesterly winds aloft. A veering wind with height in the lower part of the atmosphere is a type of directional shear often considered important for tornado development.
NMC - National Meteorological Center, with headquarters near Washington D.C.; now known as NCEP.
CMN - Centro Meteorológico Nacional, con sede cerca de Washington D.C.; ahora conocido como CNPA.
CNPA - Centro Nacional de Predicción Ambiental; versión modernizada del CMN.
NSSFC - National Severe Storms Forecast Center, in Kansas City MO; now known as SPC.
CNPTS – Centro Nacional de Predicción de Tormentas Severas, en Kansas City MO; ahora conocido como CPT.
Beaver('s) Tail - [Slang], a particular type of inflow band with a relatively broad, flat appearance suggestive of a beaver's tail. It is attached to a supercell's general updraft and is oriented roughly parallel to the pseudo-warm front, i.e., usually east to west or southeast to northwest. As with any inflow band, cloud elements move toward the updraft, i.e., toward the west or northwest. Its size and shape change as the strength of the inflow changes. See also inflow stinger.
Collar Cloud - A generally circular ring of cloud that may be observed on rare occasions surrounding the upper part of a wall cloud. See supercell.
Dust Plume - A non-rotating "cloud" of dust raised by straight-line winds. Often seen in a microburst or behind a gust front.
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) - same as towering cumulus.
Convection - Generally, transport of heat and moisture by the movement of a fluid. In meteorology, the term is used specifically to describe vertical transport of heat and moisture, especially by updrafts and downdrafts in an unstable atmosphere. The terms "convection" and "thunderstorms" often are used interchangeably, although thunderstorms are only one form of convection. Cbs, towering cumulus clouds, and ACCAS clouds all are visible forms of convection. However, convection is not always made visible by clouds. Convection which occurs without cloud formation is called dry convection, while the visible convection processes referred to above are forms of moist convection.
Elevated Convection - Convection occurring within an elevated layer, i.e., a layer in which the lowest portion is based above the earth's surface. Elevated convection often occurs when air near the ground is relatively cool and stable, e.g., during periods of isentropic lift, when an unstable layer of air is present aloft. In cases of elevated convection, stability indices based on near-surface measurements (such as the lifted index) typically will underestimate the amount of instability present. Severe weather is possible from elevated convection, but is less likely than it is with surface-based convection.
Popcorn Convection - [Slang], Showers and thunderstorms that form on a scattered basis with little or no apparent organization, usually during the afternoon in response to diurnal heating. Individual thunderstorms typically are of the type sometimes referred to as air-mass thunderstorms: they are small, short-lived, very rarely severe, and they almost always dissipate near or just after sunset.
Convección en forma de palomitas de maíz (popcorn-convection) - [Construcción vulgar], chubascos y tormentas que se forman de manera dispersa con poca o no aparente organización, normalmente durante la tarde en respuesta al calentamiento diurno. Las tormentas individuales típicamente son del tipo a veces referido, como las tormentas de masa de aire: son pequeñas, de corta vida, muy raramente severas, y casi siempre se disipan justo después y con la caída del sol.
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.
Moisture Convergence - A measure of the degree to which moist air is converging into a given area, taking into account the effect of converging winds and moisture advection. Areas of persistent moisture convergence are favored regions for thunderstorm development, if other factors (e.g., instability) are favorable.
Convergencia de Humedad - Medida del grado en que aire húmedo está convergiendo a un área dada, teniendo en cuenta el efecto de los vientos convergentes y la advección de humedad. Las áreas de convergencia de humedad persistente son regiones favorables para el desarrollo de tormentas, si otros factores (por ejemplo, inestabilidad) son favorables.
Downstream - In the same direction as a stream or other flow, or toward the direction in which the flow is moving.
Downdraft - A small-scale column of air that rapidly sinks toward the ground, usually accompanied by precipitation as in a shower or thunderstorm. A downburst is the result of a strong downdraft.
Rear Flank Downdraft (or RFD) - A region of dry air subsiding on the back side of, and wrapping around, a mesocyclone. It often is visible as a clear slot wrapping around the wall cloud. Scattered large precipitation particles (rain and hail) at the interface between the clear slot and wall cloud may show up on radar as a hook or pendant; thus the presence of a hook or pendant may indicate the presence of an RFD. See supercell.
Corriente Descendente del Flanco Trasero (o CDFT) - Región de aire seco subsidente en la cara trasera de, y envolviendo a, un mesociclón. A menudo es visible como una cuña disipante enrollándose alrededor de una nube-pared (wall-cloud). Grandes partículas de precipitación dispersas (lluvia y granizo) en la unión entre la cuña disipante y la nube-pared (wall-cloud) pueden mostrarse en el radar como un gancho o colgante; así, la presencia de un gancho o colgante puede indicar la presencia de una CDFT. Ver supercélula.
Jet Stream - Relatively strong winds concentrated in a narrow stream in the atmosphere, normally referring to horizontal, high-altitude winds. The position and orientation of jet streams vary from day to day. General weather patterns (hot/cold, wet/dry) are related closely to the position, strength and orientation of the jet stream (or jet streams). A jet stream at low levels is known as a low-level jet.
Corriente en Chorro (Jet-Stream) - Vientos relativamente fuertes que se concentran en una corriente estrecha en la atmósfera, normalmente refiriéndose a los vientos horizontales de gran altitud. La posición y la orientación de las corrientes en chorro varían de un día a otro. Generalmente los patrones de tiempo (calor/frío, húmedo/seco) están íntimamente relacionados con la posición, intensidad y orientación de la corriente en chorro (o corrientes en chorro). Una corriente en chorro en bajos niveles se conoce como chorro de bajo nivel (low-level-jet).
RUC - Rapid Update Cycle, a numerical model run at NCEP that focuses on short-term (up to 12 h) forecasts and small-scale (mesoscale) weather features. Forecasts are prepared every 3 hours for the contiguous United States.
CRA - Ciclo de Rápida Actualización, modelo numérico lanzado por el CNPA que se centra en predicciones a corto plazo (más de 12h) y características del tiempo a pequeña escala (mesoescala). Las predicciones son preparadas cada 3 horas para los Estados Unidos.
Ridge - An elongated area of relatively high atmospheric pressure; the opposite of trough.
Cresta (o dorsal) - Área elongada de presión atmosférica relativamente alta; el opuesto a vaguada.
Left Front Quadrant (or Left Exit Region) - The area downstream from and to the left of an upper-level jet max (as would be viewed looking along the direction of flow). Upward motion and severe thunderstorm potential sometimes are increased in this area relative to the wind speed maximum. See also entrance region, right rear quadrant.
Cuadrante Izquierdo Delantero (o Región Izquierda de Salida) – Área corriente abajo de y hacia la izquierda de un chorro máximo de altos niveles (como sería visto mirando a lo largo de la dirección del flujo). A veces el movimiento hacia arriba y la probabilidad de tiempo severo se incrementa en este área, en relación con el máximo de viento. Ver también región de entrada, cuadrante derecho trasero
Cuadrante Trasero Derecho - ver Región Derecha de Entrada.
*Cuerda - Embudo de condensación estrecho, a menudo retorcido, normalmente asociado con la fase de debilitamiento de un tornado. Ver fase de cuerda.
Anvil Zits - [Slang], frequent (often continuous or nearly continuous), localized lightning discharges occurring from within a thunderstorm anvil.
Cumulus - Detached clouds, generally dense and with sharp outlines, showing vertical development in the form of domes, mounds, or towers. Tops normally are rounded while bases are more horizontal. See Cb, towering cumulus.
Cumulus Congestus (or simply Congestus) - Same as towering cumulus.
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. A clear slot is believed to be a visual indication of a rear flank downdraft.
Dry Slot - A zone of dry (and relatively cloud-free) air which wraps east- or northeastward into the southern and eastern parts of a synoptic scale or mesoscale low pressure system. A dry slot generally is seen best on satellite photographs.
Anvil Dome - A large overshooting top or penetrating top.
Cúpula del yunque - Gran desbordamiento nuboso, por encima del yunque, o cima penetrante.
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