Mountain Terrain, Weather, and Hazards

Vertical-Development Clouds

Figure 1-11. Contrails.

CLOUD INTERPRETATION
1-85. Serious errors can occur in interpreting the extent of cloud cover, especially when cloud cover must
be reported to another location. Cloud cover always appears greater on or near the horizon, especially if the
sky is covered with cumulus clouds, since the observer is looking more at the sides of the clouds rather than
between them. Cloud cover estimates should be restricted to sky areas more than 40 degrees above the
horizon―that is, to the local sky. Assess the sky by dividing the 360 degrees of sky around you into
eighths. Record the coverage in eighths and the types of clouds observed.

FRONTS
1-86. Fronts occur when two air masses of different moisture and temperature contents meet. One of the
indicators that a front is approaching is the progression of the clouds. The four types of fronts are warm,
cold, occluded, and stationary.

26 July 2012

TC 3-97.61

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