This is the first time I’ve seen this natural phenomenon, although it must be quite frequent: the cloudbow. That’s a rainbow (a circular diffraction pattern caused by water droplets in the atmosphere) made by clouds, not by rain.
I walked out onto the lanai to enjoy the (extremely rare) evening sunshine. The sun had already set on Hau`Oli Mau, but it still shone on the ocean, unencumbered by Mauna Kea. There was a giant cloud right ahead of me, towards the wind. And from it rose a vertical rainbow.
The amazing thing about the cloudbow was that (as you can see in the larger image after the break) there was no rain. As a matter of fact, the cloudbow rose above the cloud, mostly.