December 08, 2020

What are the Secrets to Identifying Clouds? Part I

I often get emails and questions about clouds.  People are particularly interested in learning how to identify clouds and to understand what they imply about upcoming weather.  What is meant by the arcane compound names, such as altostratus, cirrostratus, or the intriguing altocumulus lenticularis?

Your final exam

To address these questions, I am going to write series of blogs, with this being the first, the reveals the intricacies and power of cloud identification.   Knowing about cloud identification will change your life...in a positive way.

Modern cloud identification goes back approximately 220 years to the work of Jean Baptiste de Monet Lamarck in France and Luke Howard in England in 1802-1803.

Their essential approach was to divide clouds into four types depending on how they look and three classifications based on their heights.  First, the four types based on appearance:
  • Stratus or strato-form  layered or sheet-like clouds
  • Cirrus or cirro-form:  thin, wispy clouds
  • Cumulus or cumulo-form:  puffy cotton-ball like clouds that can sometimes have great vertical development
  • Nimbus:  precipitating clouds
Let me show you some examples of each!

Here is an example of a stratus type cloud;  you see how layered it is?


A cirrus type cloud is shown below.... delicate and wispy.


A cumulus cloud has a characteristic cotton ball appearance, although some folks think they look like cauliflowers.

And then there are nimbus-type clouds, from which precipitation is falling:


Once we determine which of the four main cloud types is applicable, we then estimate the height of the clouds, dividing them into three main layers:  low, medium and high.
  • Low:  less than 2 kilometers above the surface, sometimes given the prefix strato
  • Middle: 2-7 km above the surface, often using the prefix "alto"
  • High:  more than 7 km above the surface, often using the prefix "cirro"
Low clouds are usually made of water droplets, high clouds mainly ice crystals, and the middle clouds can be both.

OK, now you are ready to put it all together.  Most cloud names combine a prefix and a suffix, the prefix denoting the height of the cloud and the suffix providing the cloud form.

For example, cirrostratus is a high ice cloud in a layer 


Altocumulus is middle-level cloud that is divided into cumulus-type elements:


And cumulonimbus is a cumulus-type cloud that is precipitating:


Well, there is a lot more to learn about cloud identification, which will have to wait until my next blog on the topic.  But you now have the essentials

But in the meantime,  you might refer to a good cloud chart, such as the online one provided by the National Weather Service (found here).






6 comments:

  1. Cliff,

    Are you going to do a blog on the blob? I've heard that it's presently quite strong and large in extent.

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  2. Thank you, Thank you! A series of blogs on clouds is almost a better gift than the five days of sunshine we recently had. When you live west of the Cascades clouds are a continual source of fascination, but also to the strictly amateur cloud watcher: confusion. So appreciated! Thank you!

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  3. so a low layered cloud is a stratostratus?

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  4. Super curious about snow making clouds and why we haven't seen anything from them this year in the lowlands? Is the blob still to blame or is la nina taking her sweet time.

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  5. Seems like something broke La NiƱa. Colder/Wetter seems to have morphed into Warmer/Drier. Whatever that is, the end result is the shoving of the blocking high pressure much farther east so its pretty much the R^3. Chicken or the Egg if the R^3 spawns the Blob or the Blob spawns the R^3. Cliff, sure hope your modeling software is grinding away with some good empirically backed theories!

    Guessing the weather this winter will end up like Seattle Sports: It doesn't get good until the last few minutes of play! So maybe in February there might be some lowland snow to smash down the daffodils in bloom and mute the rhodos.

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  6. Great article Cliff, but come on cloud height needs to be in feet not kilometers. This is from an old USAF weather observer who still enjoys guesstimating each day's clouds and their heights.

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