Introduction to Cloud Classification
Clouds are atmospheric masses of water droplets or ice crystals, classified primarily by their appearance and altitude. Scientists generally group them into ten basic types, which fall into three main altitude categories: high, middle, and low clouds. These classifications help meteorologists and observers understand and predict weather phenomena.
High-Level Clouds (above 20,000 feet)
These clouds are typically thin, wispy, and composed entirely of ice crystals due to the cold temperatures at high altitudes. The main types include Cirrus (feathery, white streaks), Cirrocumulus (small, rippled, white patches), and Cirrostratus (thin, sheet-like clouds that often produce halos around the sun or moon). They usually indicate fair weather but can signal approaching changes.
Middle-Level Clouds (6,500 to 20,000 feet)
Composed of water droplets and, when cold enough, ice crystals, middle clouds are higher than low clouds but lower than high clouds. Altocumulus clouds appear as gray or white patches or rolls, sometimes resembling sheep's wool, and can signal thunderstorms later in the day. Altostratus clouds form a uniform gray or blue-gray sheet, often covering the entire sky and typically bring widespread, continuous precipitation.
Low-Level Clouds (below 6,500 feet)
These clouds are composed mostly of water droplets and are found closest to the Earth's surface. Stratus clouds are flat, gray, and blanket-like, often bringing drizzle. Stratocumulus clouds are lumpy, gray, and patchy, rarely producing significant precipitation. Nimbostratus clouds are dark, gray, and rainy, producing continuous rain or snow, distinct from lighter, transient precipitation. Cumulus clouds are puffy, white, and often associated with fair weather, but can grow vertically into cumulonimbus clouds, which bring thunderstorms.