Cloud Types and Terms
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Typically a portion of an altocumulus cloud is shaded, distinguishing them from high-level cirrocumulus. The presence of altocumulus clouds on a warm and humid summer morning is commonly followed by thunderstorms later in the day.
Generally uniform gray sheet or layer, lighter in color than nimbostratus and darker than cirrostratus. The sun can be seen shining through them, and they frequently cover the whole sky. They are similar to lower altitude stratus clouds.
An overshooting top or dome is a protrusion of the updraft extending above the anvil level. Generally the larger and the higher one is the more intense the updraft producing it is.
They get their anvil shape from the fact that the rising air in thunderstorms expands and spreads out as the air bumps up against the bottom of the stratosphere.
Attached to cumulus, thick with ragged edges. Shelf and roll clouds are arcus clouds.
A cloud species of which at least a fraction of its upper part presents some vertically developed cumuliform protuberances (some of which are taller than they are wide) that give the cloud a crenellated or turreted appearance. Castellanus is an indication of instability at middle height (3 - 5 km) and is usually a sign of imminent thunderstorms or an active cold front.
Sometimes referred to as "lock of hair" clouds. They are composed primarily of ice crystals, reflecting the extreme cold at this height. often accompanied by tufts, leading to their common name of 'mare's tail'.
Iindicating 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. As a rear flank downdraft descends and dries out cloud and occludes around a mesocyclone.
A ring of cloud seen occasionally at the top of a wall cloud (usually in wall clouds that are rotating) where the wall cloud is attached to the updraft base above it.
Consisting of condensed water droplets
Cumulus is Latin for pile. A strongly sprouting cumulus species with generally sharp outlines and, sometimes, with a great vertical development; it is characterized by its cauliflower or tower aspect, of large size.
They can exist as individual towers or form a line of towers called a squall line. Fueled by vigorous convective updrafts (sometimes in excess 50 knots), the tops of cumulonimbus clouds can easily reach 39,000 feet (12,000 meters) or higher. Associated with powerful thunderstorms known as supercells.
Usually low altitude. "Cottonwool" clouds.
Near or on the ground, often appearing beneath a condensation funnel and surrounding the base of a tornado.
The extremities of these filaments are always thin and never terminated by tufts or hooks. This species is found mainly in the genera cirrus and cirrostratus. Cirrostratus fibratus may develop from cirrus fibratus or cirrus spissatus.
Each cloud element is a small tuft with a cumuliform or rounded appearance, the lower part of which is more or less ragged and often accompanied by virga.
. Fractus have irregular patterns, appearing much like torn pieces of cotton candy, change constantly, often forming and dissipating rapidly. They do not have defined base. Common kinds are scud and "cloud tags"
If the rotation is violent and in contact with the ground, the vortex is a tornado. Funnel clouds can occur through a variety of processes in association with convection. For example, small funnel clouds are infrequently seen extending from small, dissipating cumulus clouds in environments with significant vertical wind shear in the cloud-bearing layer.
It is then given the name of the appropriate genus, followed by the name of the genus of the mother-cloud with the addition of the suffix “genitus” (e.g., stratocumulus cumulogenitus).
Due to decreased temperature and increased moisture leading to saturation in a very shallow layer near the surface. It most often occurs when there is a warm, humid layer atop the hail and when wind is light.
Latin for humble. With uniform height
Latin for anvil. Also called anvil, anvil cloud, thunderhead. A supplementary cloud feature peculiar to cumulonimbus capillatus; the spreading of the upper portion of cumulonimbus when this part takes the form of an anvil with a fibrous or smooth aspect.
Can occur at lower or mid levels of a tower. They may indicate the strength of the inflow of moist air into the storm, and, hence, its potential severity.
They usually appear on the upwind side of a back-sheared anvil, and indicate rapid expansion of the anvil due to the presence of a very strong updraft.
Characterized more by the appearance of the spaces between the cloud elements than by the elements themselves.
Formed by standing waves of wind passing mountains or hills. Can look like giant flying saucers or lopsided stacks of pancakes.
Unique to the genus cumulus, of moderate vertical development, the upper protuberances or sproutings of which are not very marked; it may have a small cauliflower aspect. This cloud does not give any precipitation, but frequently develops into cumulus congestus and cumulonimbus.
This species is found principally in the genera cirrostratus and stratus. Stratus nebulosus is the most common species of stratus. Cirrostratus nebulosus produces halo phenomena.
See a nimbostratus and you'll be getting wet for a long time
This variety is found in the genera altocumulus, altostratus, stratocumulus, and stratus.
These shreds may constitute a layer, which may be separated from the main part of the cloud, or attached to it. This accessory cloud occurs mostly with nimbostratus, cumulus, and cumulonimbus.
A cloud variety, usually of the species stratiformis, in which distinct spaces between its elements permit the sun, moon, blue sky, or higher clouds to be seen. These openings may be very small. This variety is found only in the genera altocumulus and stratocumulus.
Also called cap cloud, scarf cloud. An accessory cloud of small horizontal extent, often cirriform, in the form of a cap, hood, or scarf, which occurs above or attached to the top of a cumulus or cumulonimbus (less often stratocumulus) cloud that often pierces it. Sometimes several pileus clouds are observed above each other. Pileus is formed as a moist layer locally lifted due to rising cloud below.
Owing to the effect of perspective, these bands seem to converge toward a point on the horizon. This variety occurs in the genera cirrus, altocumulus, altostratus, and stratocumulus, and may modify many of the species, but principally stratiformis.
Associated with a thunderstorm gust front (or sometimes with a cold front). Roll clouds are relatively rare; they are completely detached from the thunderstorm base or other cloud features, thus differentiating them from the more familiar shelf clouds.
Frequently visible in satellite imagery along a front or other boundary.
Often attached to the underside of Cb. Associated with a thunderstorm gust front.
Unique to the genus cirrus, of such optical thickness as to appear greyish on the side away from the sun, and to veil the sun, conceal its outline, or even hide it.
A bit like a plate full of dumplings
A low sun angle creates the striation effect by differential shadowing of varying cloud levels.
Usually is observed extending from the wall cloud toward the north or northeast. Cloud tags extending from a wall cloud towards a precipitation core. An area of condensation consisting of laminar ban.
Sufficiently translucent to reveal the position of the sun, or through which higher clouds may be discerned.
Previously called a tuba. Aka. pendant cloud, tornado cloud. This supplementary feature occurs mostly with cumulus and cumulonimbus; when it reaches the earth's surface it constitutes the cloudy manifestation of an intense vortex, namely, a tornado or waterspout.
Often in the form of a comma, topped with either a hook or a tuft that is not rounded. The species uncinus is unique to the genus cirrus. The hook takes the shape of a reverse question mark under positive wind shear (wind increasing with height) conditions and the shape of a question mark under negative wind shear.
Also called billow clouds, windrow clouds, wave clouds.
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