Low Clouds

AVIATION WEATHER

CHAPTER TWO

Low Clouds

Cloud bases in this category range from just above the surface to 6500 feet AGL (Figure 2-14).

Low clouds are mainly composed of water droplets. The low clouds have no special prefix

attached to their name. However, if the word nimbo or nimbus appears, beware, these clouds are

producing violent or heavy precipitation.

Nimbostratus, a stratiform cloud, produces heavy steady precipitation.

Figure 2-14 Stratus

Low clouds frequently present serious hazards to flying. The most serious hazard is the

proximity of the cloud base to the surface of the Earth. Some of the low cloud types hide hills,

making a collision with the terrain a very real danger, and visibility within low clouds is very

poor. Low clouds may also hide thunderstorms. If the clouds are at or below freezing

temperatures, icing may result. Icing accumulates faster in low clouds since they are generally

denser than middle and high clouds. Turbulence varies from none to moderate. Expect

turbulence in and below the clouds. Precipitation from low clouds is generally light rain or

drizzle.

Atmospheric Mechanics of Winds, Clouds and Moisture, and Atmospheric Stability

2-17