Which Clouds Are Low & Gray?

Cloud Types

• Clouds are classified by their height and form. There are three levels of clouds: high-level, mid-level and low-level. High-level clouds occur above 20,000 feet and are known as cirrus clouds. Mid-level clouds occur between 6,500 and 20,000 feet and are known as alto clouds. Low-level clouds occur below 6,500 and do not have a prefix. There are two general forms of clouds: cumulo and strato. Cumulo clouds are puffy and have vertical development. Strato clouds are layered and have almost no vertical development. There are three types of low, gray clouds: cumulus, status and stratocumulus.

Stratus Clouds

• Stratus clouds are gray and uniform. They appear featureless and can blanket the entire sky, known as overcast conditions. They often look like layers of fog that do not reach the ground. Stratus clouds are formed when large layers of air are gradually lifted or cooled from below. They are commonly associated with warm fronts, which cause their moist air to slowly rise. Stratus clouds can produce light mist or drizzle; however, when they begin to produce heavier precipitation, their name is changed to nimbostratus. Stratus clouds can signal the approach of long periods of continuous rain, from several hours to several days.

Cumulus Clouds

• Cumulus clouds are gray and puffy. They begin as white clouds but progress to dark gray as they swell with moisture. They typically have sharp, well-defined outlines and flat bases. Cumulus clouds are also much more isolated than stratus clouds, often with blue skies between them. Cumulus clouds feature vertical development. They form as water vapor condenses in strong, upward air currents. They are commonly associated with cold fronts, which act as giant wedges, forcing warm, moist air to rise rapidly. Cumulus clouds can produce light sprinkles; however, like stratus clouds, when they begin to produce heavy rain, their name is changed to cumulonimbus. These clouds can develop into thunderstorms, towering to heights of 50,000 feet or more. They produce severe weather that is short-lived, as opposed to steady, lengthy precipitation.

Stratocumulus Clouds

• Stratocumulus clouds are a like a combination of stratus and cumulus clouds. They form in strong horizontal surface winds. As these winds flow over the surface, friction produces turbulence. This turbulence causes a layer of stratus clouds to rise and fall, producing a low layer of lumpy, gray clouds. The turbulence is confined near the surface. Therefore, stratocumulus clouds reflect more horizontal development than vertical. These clouds typically move much faster than cumulus clouds and are much less defined. Stratocumulus clouds rarely produce more than occasional light precipitation.