Phoning in New Clouds: Part 3 – Meet the Newest Clouds

January 29, 2019
Doomsday Cloud

The Doomsday cloud, Undulatus Asperatus.

NASA/Witta Priester

As I’ve mentioned before, twelve new cloud types were announced this past year. Some of the most interesting are what we call the “special” and accessory clouds …

(The photo above shows the “Doomsday” cloud, Undulatus Asperatus, which I shared in my last post on new cloud discoveries.)

What’s an accessory cloud? This is a cloud that accompanies another. Believe me, you would rather see the picture than have one coming at you.

The new accessory cloud is called a “flumen” and is a low cloud associated with severe supercell storms. They move towards but are not attached to thunderstorm clouds, (cumulonimbus), carrying warm wet air. They feed the storm, sometimes supplying enough moisture and energy for tornado development. 


Feeding the storm: : A Flumen cloud Source: WMO, International Cloud Atlas

Five other new clouds are “special” clouds which are weirdly-created Frankenstein clouds that are unusually made. Instead of forming due to the humidity and temperature variations in the upper atmosphere, these clouds are created by conditions on the Earth’s surface or conditions created by living organisms. Their Latin names are truly intimidating mouthfuls. Two are:

  • Cataractogenous, describing clouds that develop from the spray of large waterfalls, and
  • Flammagenitus, describing clouds formed by wildfires.


Water and fire clouds: Cataractogenous and Flammagenitus clouds are created by surface conditions. Source: Wikipedia

Living things can create clouds as well. One, newly recognized, is Silvagenitus, clouds formed under the influence of moisture from respiring trees. The woodlands carry moisture from their roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. You can see it rising like steam and forming clouds.


Silvagenitus, the forest clouds Source: WMO, International Cloud Atlas

Two types of special clouds are made by man:

  • homogenitus, describing clouds formed by human activities, such as airplane contrails and power plant steam, and
  • homomutatus, describing clouds originally made by humans that gradually transform into more natural-looking forms, like a contrail that eventually spreads in the wind.


The clouds we make: Homogenitus (Source: Wikipedia) and Homomutatus (Source: WMO, International Cloud Atlas)

Those are all for now. Keep your cell phones out. The next new clouds could be discovered by you!


About This Blog

Are you a weather watcher? Welcome to “Weather Whispers” by James Garriss and until recently, Evelyn Browning Garriss. With expertise and humor, this column covers everything weather—from weather forecasts to WHY extreme weather happens to ways that weather affects your life from farming to your grocery bill. Enjoy weather facts, folklore, and fun!

With heavy hearts, we share the news that historical climatologist and immensely entertaining Almanac contributor Evelyn Browning Garriss passed away in late June 2017. Evelyn shared her lifetime of weather knowledge with Almanac editors and readers, explaining weather phenomena in conversation and expounding on topics in articles for the print edition of The Old Farmer’s Almanac as well as in these articles. We were honored to know and work with her as her time allowed, which is to say when she was not giving lectures to, writing articles for, and consulting with scientists, academia, investors, and government agencies around the world. She will be greatly missed by the Almanac staff and readers.