Clouds and Weather Predictions

Cumulonibus

Have you ever wondered how to predict the weather by watching the clouds? Yesterday I wrote on how recognize the basic cloud types, and today I want to share what each type of cloud has to say about the weather. Obviously, we all know that the rolling, towering “thunderheads” like those above foretell heavyweather, very likely with lightening, thunder, and downpours or hail. But, not all of us are sitting by a window where the weather is obvious all the time. Whenwe wake up early in the morning and want to know what the day is likely to bring, what can we do in addition to checking out the local weather report?Cirrus

Starting at “the top” (of the sky): Wispy cirrus clouds in a blue sky normally mean clear weather, but they often signal a changing weather pattern coming.Cirrocumulus above Altocumulus above Stratus

Cirrocumulus clouds are very rare. They are formed completely from ice crystals but usually mean that a cold front is coming in and appear just before a rainfall or snowfall. In the picture above, you can see all three cloud layers, and it was, in fact, raining under the low, stratus clouds in the background.

Cirrocumulus clouds above a “Mackeral Sky”   

Cirrocumulus clouds usually appear in the winter and are a sign of cold, mostly clear weather. However, if the clouds begin to thicken and bunch up, they become are known as a mackeral sky (so named because it looks like ripples of mackeral fish scales). Mackeral skies can form either high up as cirrocumulus clouds, or—as the clouds grow heavier and descend into the mid-level —as altocumulus clouds. In either case, they portend heavy weather. As the folk saying goes: “A mackeral sky means there’s rain nearby.”

Cirrus clouds over Altocumulus clouds

If you’ve ever seen the sky looking white and hazy with a rainbow around the sun, you’re looking through cirrostratus clouds. The ice crystals bend the rays of the sun and make beautiful prisms in the sky. I don’t actually have a picture of this situation, but I did catch a circular pattern of rainbows on the clouds one day that really fascinated me! The adage for this one is: “Rainbow sun or moon…precipitation soon.”

Cirrostratus clouds above Altocumulus clouds

Cirrostratus clouds usually signal changing weather with precipitation likely in the next 12-24 hours. You can watch the drift of the streaks to get an idea of the direction from which storm may come.  Altocumulus clouds are growing heavy with water droplets and appear grey and irregular.

Altocumulus clouds above Cumulus clouds

It is said that if you see altocumulus clouds in the morning on a warm, humid day, get ready for thunderstorms that afternoon!

Cirrostratus clouds above Altocumulus clouds with an “Anvil Head”

Sometimes cumulus clouds swell to huge proportions, becoming up to 30,000′ high! When you see a huge cumulus cloud with a flat top, looking like an anvil, this indicates that a high wind has sheared off the top and heavy weather is ahead. At that point, the cumulus cloud adds the suffix “nimbus” to its title.Altocumulus clouds above Cumulonimbus clouds

Cumulonimbis clouds usually forecast the most extreme weather, including thunderstorms, torrential downpours, hail, snow, tornadoes, and hurricanes.

Cumulus Clouds

But not all cumulus clouds are threatening! The cumulus clouds that look like white cotton balls without much vertical development usually signal fair, dry conditions. If they bring showers at all, the precipitation will usually be light and only last briefly. One of the happy sayings for cumulus clouds in spring is: “April showers bring May flowers.”

Cirrostratus clouds above Altrostratus clouds

The last type of clouds to understand are the “stratus” (flat, covering) clouds. Altostratus clouds often appear a few hours before a warm front and precipitation.

Altostratus clouds above Stratocumulous and Nimbostratus clouds

Rain rarely occurs with stratocumulus clouds. They look like masses of puffy, grey clouds with little spaces between them and usually indicated dry weather unless there’s a big temperature difference between night and day, in which case there may be light precipitation. Stratocumulous clouds can turn into nimbostratus clouds, though, as pictured above (notice formation at right).

Nimbostratus clouds

Nimbostratus clouds often produce a dark, grey covering over the sky that will bring light to moderate precipitation but of long duration and over a widespread area. Nimbostratus clouds can leave us with a beautiful, soft covering of snow below as well as above.Stratus clouds

Stratus clouds form a dull, greyish-white blanket, often across the entire sky. This is what the sky looked like at my home early this morning…a typical “overcast” day. Stratus clouds usually produce only drizzle or fine snow, if anything at all. This is what ours brought:

Alan wants his dinner, so I’d better quit. I hope this was fun and might even be helpful! Here are a few last bits of folklore with some science behind them:

“The higher the clouds, the finer the weather.”

“When clouds appear like towers, the earth is refreshed by showers.”“Red sky at night: sailors delight; red sky in the morning: sailors take warning.”

“The heavens declare the glory of God, and the firmament shows his handiwork.” (Psalm 19:1)

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