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That’s a great example of a pileus us cloud, Michael. Well spotted!
For those who don’t know, the name comes from the Latin for a ‘hat’. It’s a smooth cap of cloud that forms momentarily over a developing convection cloud (usually a Cumulus congestus) as the air rising from below lifts an airstream passing overhead. As this airstream is lifted, it can cool enough for some of its moisture to form into droplets which we see as a smooth patch of cloud. Inevitably, the building Cumulus cloud carries on growing higher and subsumes the pileus above.
Hi, Marsha. What you saw is known as a ‘lunar halo’. This forms when the moonlight is refracted, and so bent, as it shines through the minuscule ice crystals of a high cloud like Cirrostratus. The crystals have to be shaped like tiny hexagonal columns or plates which act like tiny prisms. The optics are the same as a ’22-degree halo’ around the sun. But because moonlight is so much dimmer than sunlight, it can be difficult to see the colours of a lunar halo, and it is a hard optical effect to photograph. Here are some images of lunar halos on the Society gallery:
https://cloudappreciationsociety.org/gallery/photo-n-3719/
https://cloudappreciationsociety.org/gallery/photo-n-2849/
https://cloudappreciationsociety.org/gallery/photo-n-2578/Also, I discussed the effect (and mentioned the lunar version) in a chat with the Weather Channel recently:
Paul,
Yes, this is a great combination! Waves and clouds are, in my opinion, great bedfellows. Thanks for posting the link!I signed up to this petition when it first launched. It would be terrible if the building was allowed to fall down. Private Eye published a piece about it this week:
God point, Jim. We will bear this in mind at the next Enamel Badge Design Steering Group meeting. A white cloud might work. Do any other members have opinions on this?
I’ve included your image here so others can see.
It is not easy to say for sure whether this is a contrail. It seems the most likely explanation to me. Does anyone else have any thoughts on what the formation might be…?
Cloud formations described as gravity waves are completely different things from the gravitational waves that Einstein predicted. The clouds are formed by mechanical waves that are periodic movements of the air propelled by the restoring force of gravity. Ocean waves are also gravity waves. Gravitational waves are waves in the space-time continuum – i.e. waves in the very fabric of space.
Bizarrely, I once had dinner at Professor Stephen Hawking’s house in Cambridge to interview Professor Kip Thorne, the world authority on gravitational waves. This was for the waves book I wrote back in 2010. It is amazing that they have now finally been discovered.Hi Catherine,
It’s a cloud shadow being cast down from the summit of a distant storm cloud. So yes, crepuscular rays. The shadow shows up as the sunlight is scattered by a thin layer of Cirrostratus cloud just below the summit. The shadow looks like it is going up because of the effect of perspective. It works like this:We shared a similar one on our Instagram feed recently that had been submitted through the CloudSpotter app.
The colours around the edge of the storm cloud are called iridescence. They’re caused by the sunlight being separated into its constituent wavelengths as it is diffracted around the droplets at the fringes of the cloud.
I hope you are enjoying Cambodia!
Gini, we hope you are bearing up ok. How about this one over California by Christine Murphy?
With best wishes, GavinIt’s great that you have started a local page, Lobke. I’ll link to it from the main CAS Facebook page.
When the website redesign, which we have been working on for some time, is ready, users of the forum will be able to upload a profile picture. In the meantime, you can email us the image you would like for your profile and we will set it for you. Just send it to members@cloudappreciationsociety.org, along with your membership number and we’ll sort it out.
Sorry it is a bit clunky at the moment. Hopefully, we will have the site redesign in place before too long.We loved meeting you all on Saturday. The enthusiasm and positivity from out attendees meant so much to us. The security guard at the RGS, who has worked at their events for many years, told me it was unprecedented to hear not a single negative comment as people were coming out.
Thank you all for making the effort to come – some from great distances – and for helping make it such a significant and memorable day for the Society!
