Did you know that ordinary rain and thunderstorms come from completely different kinds of clouds? Learn about nimbostratus clouds, which form at warm fronts and make ordinary rain and snow.
What Nimbostratus Clouds Look Like
Everyone knows that rain comes from clouds, but not all clouds make rain. If you look up at the sky and see just a few wispy white clouds very high up you know it’s probably not going to rain. But if you see a thick layer of dark clouds coming your way, you can tell that it’s time to go grab your umbrella. If you’ve ever done that, then you’ve already seen nimbostratus clouds in action.Nimbostratus clouds are dark gray and thick enough to hide the sun completely. Unlike some other clouds, they don’t come in different shapes.
You can’t look up at a nimbostratus cloud and guess what the shape of the cloud looks like – it just looks flat and gray, like a big cloud blanket over the whole sky.
Nimbostratus clouds can float as low as 2,000 meters (just over 1 mile) above the ground, which is pretty low for a cloud. For comparison, airplanes fly between 6 and 7 miles above the ground. It’s sometimes hard to tell where the bottom of a nimbostratus cloud really is, because there can be fog or other clouds in the way.
The Name Says it All
The name ‘nimbostratus’ comes from two Latin words:
- ‘nimbus’ means rain or a rain-cloud
- ‘stratus’ means something layered or spread out
That’s a perfect name because it tells you exactly what you’re getting with these clouds: a big layer of rain clouds spread out across the whole sky.
Rain from Nimbostratus Clouds
Steady rain usually falls from nimbostratus clouds, but it’s just ordinary rain. Big thunderstorms, lightning, and hail come from cumulonimbus clouds, not nimbostratus clouds.If it’s cold enough, nimbostratus clouds can make snow instead of rain.
If you’ve ever gone to bed in the winter and woken up to six inches of new snow in the morning, that snow probably fell from a nimbostratus cloud.
Nimbostratus clouds can also make rain that never touches the ground at all. Sometimes, the raindrops are so tiny that they evaporate before they ever reach the earth. This is called virga.
If a nimbostratus cloud is making virga, then you’ll look up and see a gloomy gray sky, but you won’t feel any raindrops because all the rain is going on above your head.
How Nimbostratus Clouds Form
Nimbostratus clouds form from another type of cloud, altostratus clouds. Altostratus clouds usually form at warm fronts, or places where warm air is blowing across the land and meeting colder air in its path. When an altostratus cloud gets thicker and lower to the ground, it turns into a nimbostratus cloud.
Nimbostratus clouds aren’t very common at the equator or at the poles. They’re most common in parts of the earth where the weather isn’t very hot or very cold.
Nimbostratus clouds are low-hanging, dark gray clouds that block the sun completely. They make steady rain or snow, but not thunderstorms or lightning. They form at warm fronts from altostratus clouds that sink lower to the ground and get thicker.