If you’ve ever seen a sunrise or sunset that took your breath away, chances are good that there were wispy clouds on the horizon reflecting the pinks and oranges of the sun. The fact that those clouds were probably cirrus clouds likely didn’t cross your mind. We don’t typically think about clouds in those terms.
But there are, in fact, many different types of clouds in endless shapes and sizes, and they can signal good weather and bad.
Each type plays a role in helping meteorologists and weather spotters predict upcoming weather conditions, which, with practice, is something you can also learn to do. Boning up on the study of clouds can certainly save you from getting soaked in a storm, but it can also just be fun. Here are the basics to get you going.
Cloud Types by Shape
The National Weather Service says there are four main categories of clouds:
- Cirro-form: Derived from the Latin word “cirro,” meaning “curl of hair,” this term describes whitish, wispy clouds composed of ice crystals. They typically are the first types of clouds to appear in the sky before a storm system, the NWS says.
- Cumulo-form: The quintessential puffy cloud, these white, cotton ball-like formations are typically detached with a flat base.
- Strato-form: When you look up to see a nearly uninterrupted layer of clouds blocking your view of the sky, you’re likely seeing strato-form clouds. (“Strato” means “layer” in Latin.)
- Nimbo-form: In Latin, the word “nimbus” means “rain” — and these tall clouds produce the majority of precipitation, according to the NWS.
A Closer Look
Each cloud in the sky is unique, and many clouds boast features from multiple categories. So, the four main types of clouds are broken into sub-groups, based on their distance from the ground, according to the National Weather Service. Low-level clouds occur below 6,500 feet; mid-level clouds appear between 6,500 and 20,000 feet; and high-level clouds are 20,000 feet and above.
- Stratus (Low-level): These featureless layers of clouds are low to the ground and appear as an even, flat layer of gray across the sky. They can cause light precipitation, the NWS says, or they can just block out the sun, leaving gloom behind.
- Stratocumulus (Low-level): As the name indicates, these are a combination of fluffy cumulus clouds clumped together in a strato-form layer. The NWS says they often appear before or after a frontal system.
- Cumulus (Low-level): These are individual, dense clouds that develop vertically, with tops that are often described as looking like cauliflower. There are several types of cumulus clouds, depending on how tall they’ve grown, the NWS says. “Fair-weather” or “flat” cumulus are often seen on an otherwise sunny day, while cumulus with higher tops, sometimes called “towering” cumulus, can develop into our next type of cloud, the cumulonimbus.
- Cumulonimbus (Low-level): Sometimes thought of as a “thunderstorm cloud,” this is is a dense, dark cloud in the form of a mountain or tower (sometimes with a flat peak). The NWS says these clouds can produce thunderstorms with heavy rain.
- Nimbostratus (Low-level): Dark gray and ominous, these clouds often cover the sky in a layer. The NWS says nimbostratus clouds can produce steady rain or snow.
- Altostratus (Mid-level): These are thick, flat clouds appearing a bit higher in the sky that rarely produce more precipitation than a light shower. They usually hail the approach of warmer air, which can cause them to descend and eventually release snow or rain, depending on the season, according to the NWS.
- Altocumulus (Mid-level): The National Weather Service describes these clouds as “heap-like,” and says they often group together in rows, with clear areas in between. According to the National Earth Science Teachers Association’s Windows to the Universe, a morning sky full of altocumulus may mean thunderstorms that afternoon.
- Cirrus (High-level): These feathery, wispy clouds appear high in the sky and, according to the NWS, may mean a warm front is on the way.
- Cirrostratus (High-level): As a warm front approaches, cirrus clouds can thicken into cirrostratus clouds, forming a layer of wispy white high in the sky. The cirrostratus can then thicken and descend, becoming altostratus or nimbostratus.
- Cirrocumulus (High-level: Often appearing as rows of clumpy white or gray in the sky, these clouds often appear on fair, cold winter days, according to Windows to the Universe.
Not every white, puffy form in the sky fits into these categories — contrails, the cloudy streaks that appear behind airplanes, are one example. But, this guide can help you begin to recognize the difference between a sunny cirrus and a storm-bringing cumulonimbus, and hopefully spark your interest to learn more about clouds.
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