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Predicting the weather using clouds

Fair Weather Cumulus Clouds


Fair weather cumulus clouds are fantastic as they indicate that it won’t rain for the rest of the day if you see them after mid-morning.


These are the cute white fluffy clouds that are wide rather than tall - they are typical summer day clouds.

Cirrus Clouds


Cirrus clouds are easy to identify. They are the highest clouds in the sky and are made up of wisps or streaks of ice crystals.


They indicate that it is about 12-24 hours before a warm front will arrive, and this means that it will rain for about 4 hours before its arrival.


Cirrus are nicknamed mare’s tails, from the streaks of ice crystals that fall beneath them.


However, don’t assume that cirrus clouds always mean rain is coming; sometimes they can mean the exact opposite, so to be more confident of your forecast it is important to use other signs, like the ones below.

Cirrostratus Clouds


Cirrostratus clouds are a thin veil of ice crystals that cause a halo around the sun or moon. They indicate that a warm front is coming in around 12 hours, which means that rain is about 8 hours away.


These clouds are fab for confirming if any cirrus clouds present are indicating a depression, as they aren’t often seen without the approach of a warm front.


As the warm front nears, the cirrostratus clouds will thicken and lower until they become altostratus clouds.

Altostratus clouds


Altostratus clouds are the next clouds that are spotted before the approach of a warm front. They are dull, relatively featureless layer clouds and they indicate that it will rain in about four hours. The sun can often be seen through them, but it won’t cast a shadow on the ground.


As with most other clouds seen in the build-up to a warm front, if you see them on their own they don’t necessarily indicate a front is approaching, so you should use one of the above signs too.


However, they are a very strong sign of the approaching front, and if you have already seen cirrus clouds in the hours before you see altostratus, then you can be very confident that the front is arriving.


The altostratus clouds will again lower and thicken into rainy nimbostratus clouds, which will bring increasingly heavier rain for the next four hours. Then the weather will improve, at least temporarily, after the front has passed through.



Pannus Clouds


Pannus clouds, which are grey fragmented or streaks of cloud that are seen below the main cloud base, indicate rain in just about 10 minutes, and they are a great indicator of when the nimbostratus clouds will arrive before a warm front.

Nimbostratus Clouds


Nimbostratus clouds are dark, grey, featureless layers of cloud, thick enough to block out the Sun and produce persistent rain.


These mid-level clouds are often accompanied by continuous moderate rain or snow and appear to cover most of the sky. Nimbostratus will often bring precipitation which may last for several hours until the associated front passes over.


If there is hail, thunder or lightning present it is a Cumulonimbus cloud rather than Nimbostratus.

Cumulonimbus Clouds


Cumulonimbus clouds are the tall cumulus clouds that bring heavy showers, blustery wind and sometimes thunder.


They are either isolated shower clouds, especially in the summer, or form part of a unsettled weather pattern bringing a cold front in the winter.

Stratocumulus Clouds


Stratocumulus clouds are a combination of cumulus and low level stratus clouds. They can be vary greatly in form, but they usually suggest light winds and days of similar conditions, especially when they are seen in the winter.


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