Cloudy with a chance of…
By Lisa Densmore
You learned the four basic players in elementary school — cumulus, nimbus, stratus and cirrus. Take your knowledge as an armchair weatherman to the next step and learn what happens when these clouds combine … and what it means for your time afield.
Cirrostratus: Cirrus clouds forming a sheet across the sky at a very high elevation Forecast: Approaching warm front. Precipitation in 12 to 24 hours |
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Cirrostratus with halo: An intensifying sheet of very high clouds, barely discernible at first except for a halo around the sun or moon Forecast: Cloud ceiling is lowering. Possibility of precipitation within 48 hours |
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Cirrocumulus: Very high clouds that look like a mass of puff balls or fish scales rather than wisps Forecast: Fair but cold weather now. Precipitation may be on its way due to an unstable air mass. In tropical regions, cirrocumulus clouds may indicate an impending hurricane, thus the expression, "mackerel sky, storm is nigh." |
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Altocumulus: Similar to cirrocumulus clouds but lower Forecast: Precipitation or thunderstorm within 24 hours. If you see altocumulus clouds in the morning, keep your rain gear handy. You'll likely need it after lunch. |
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Cumulonimbus: Massive cumulus clouds, often with anvil-shaped tops Forecast: Take cover! An intense downpour and possibly hail is imminent and probably accompanied by a violent thunderstorm, but it should be over in 20 minutes. |
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Cumulocongestus: The precursor to cumulonimbus clouds, but still forming. The top is uneven and growing higher and higher Forecast: Unstable air mass. A thunderstorm is coming, but you've got a little more time than with cumulonimbus clouds. |
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Fair Weather Cumulus: Puffy white clouds that form later in the day. They may form in lines across the sky, indicating the direction of the breeze Forecast: The air mass is stable. Enjoy the rest of a beautiful day. |
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Altostratus: Medium-high clouds that turn the sky medium-gray. You can see a bright spot where the sun is Forecast: Light precipitation may fall now. Expect rain within 48 hours if the sky gets darker. |
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Nimbostratus: Low, dark, thick clouds with ragged edges and undefined shapes. Also called "scud clouds." Forecast: It's going to rain steadily all day. |
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