1959 US Army Vietnam War Terrain Intelligence ... - Survival Books

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0 I 2 3 4
two or
no clouds one-tenth three-tenths four- tenths five-tenths
5 6 7 8 9
seven or nine completely sky
six-tenths eight-tenths tenths covered obscured
Figure 9. Cloud coverage symbols.
(1) Clear. No clouds, or less than 0.1 of the sky covered.
(2) Scattered. 0.1 to 0.5 of the sky covered.
(3) Broken. 0.6 to 0.9 of the sky covered.
(4) Overca.st. More than 0.9 of the sky covered.
a. Cloud heights are reported in hundreds of feet above the ground.
The heights of clouds below 5,000 feet are reported to the nearest 100
feet; clouds from 5,000 to 10,000 feet, to the nearest 500 feet, and
clouds above 10,000 feet to the nearest 1,000 feet. The term ceiling
is used by forecasters to give an indication of the amount and height
of the bases of the clouds. It is defined as the lowest height (altitude)
at which all clouds at or above that altitude cover more than one half
of the sky. H]eighits are generally considered in relation to the main
level of the terrain in the vicinity.
d. Cloud direction is the direction from which the clouds are
moving. It is reported according to the eight points of the compass.
e. According to their appearance, clouds are either cumilifornm or
stratiform. Cmniliform clouds are formed by rising currents in unstable
air. Stratiforml clouds result from the cooling of air in stable
layers.
(1) Cumliliforn clouds are dense with vertical development.
The upper surface of a cumiliform cloud is dome-shaped,
while the base is nearly horizontal. Usually clouds of this
type are separate from each other and rarely cover the entire
sky. The precipitation from cumiliform clouds generally is
showeerv in nature.
(2) Stratiforil clouds usually occur in layers that may extend
from horizon to horizon, without the vertical development of
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