
.topic 40
White or grey, or both white and grey, patch, sheet or layer of cloud, generally with shading, composed of laminae, rounded masses, rolls, etc., which are sometimes partly fibrous or diffuse and which may or may not be merged; most of the regularly arranged small elements usually have an apparent width between one and five degrees.


.topic 50
Greyish or bluish sheet or layer of striated, fibrous or uniform appearance, totally or partly covering the sky, and having parts thin enough to reveal the sun at least vaguely, as through ground glass. Altostratus does not show halo phenomena.


.topic 60
Thin, white patch, sheet or layer of cloud without shading, composed of very small elements in the form of grains, ripples, etc., merged or separate, and more or less regularly arranged; most of the elements have an apparent width of less than one degree.


.topic 70
Transparent, whitish cloud veil of fibrous (hairlike) or smooth appearance, totally or partly covering the sky, and generally producing halo phenomena.


.topic 80
Detached clouds in the form of white, delicate filaments or white or mostly white patches or narrow bands. These clouds have a fibrous (hair-like) appearance, or a silky sheen, or both.


.topic 90
One or more sequences (seldom more than three) of coloured rings of relatively small diameter, centred on the sun or moon.


.topic 100
Heavy and dense cloud , with a considerablevertical extent, in the form of a mountain or huge towers. At least part of its upper portion is usually smooth, or fibrous or striated, and nearly always flattened; this part often spreads out in the shape of an anvil or vast plume.


.topic 110
Detached clouds, generally dense and with sharp outlines, developing verically in the form of rising mounds, domes or towers, of which the bulging upper part often resembles a cauliflower. The sunlit parts of these clouds are mostly brilliant white; their base is relatively dark and nearly horizontal. Sometimes Cumulus is ragged.


.topic 120
Fairly uniform precipitation composed exclusively of fine drops of water (diameter less than 0.5 mm), very close to one other.

.topic 130
Precipitation of small balls or pieces of ice (hailstones) with a diameter ranging from 5 to 50 mm or sometimes more, falling either separately or agglomerated into irregular lumps

.topic 140
An optical phenomenon in the form of a ring, arc, pillar or bright spot, produced by the refraction of light by ice crystals suspened in the atmosphere (cirriform clouds, ice fog, etc.). This phenomenon, when formed by refraction of the light of the sun, may show colors, while a halo phenomenon produced by the light of the moon is always white.




.topic 150
Precipitation of transparent or translucent pellets of ice, which are sperical or irregular, rarely conical, and which have a diameter of 5 mm or less


.topic 160
A fall of unbranched ice crystals, in the form of needles, column's or plates, often so tiny that they seem to be suspended in the air. These crystals may fall from a cloud or from a cloudless sky.


.topic 170
A luminous manifestation accompanying a sudden electrical discharge which takes place from or inside a cloud or, less often, from high structures on the ground or from mountains.

.topic 180
Grey cloud layer, often dark, the appearance of which is rendered diffuse by more or less continuously falling rain or snow, which in most cases reaches the ground. It is thick enough throughout to blot out the sun. Low, ragged clouds frequently occur below the layer, with which they may or may not merge.


.topic 190
Precipitation of liquid water particles, either in the form of drops of more than 0,5 mm diameter or of smaller widely scattered drops.


.topic 200
Precipitation of very small white opaque grains of ice. These grains are fairly flat or elongated; their diameter is generally less than 1 mm.


.topic 210
Precipitation of ice crystals, most of which are branched (sometimes star-shaped).


.topic 220
Grey or whitish, or both grey and whitish, patch, sheet or layer of cloud which almost always has dark parts, composed of tessellations, rounded masses, rolls, etc., which are non-fibrous (except for virga) and which may or may not be merged; most of the regularly arranged small elements have an apparent width of more than five degrees.


.topic 230
Generally grey cloud layer with a fairly uniform base, which may give drizzle, ice prisms or snow grains. When the sun is visible through the cloud, its outline is clearly discernible. Stratus does not produce halo phenomena except, possibly, at very low temperatures. Sometimes Stratus appears in the form of ragged patches.



.topic 360
A sharp or rumbling sound which accompanies lightning

.topic 370
Vertical or inclined trails of precipitation (fallstreaks) attached to the under surface of a cloud, which do not reach the earth's surface.


