Unusual Rainbow Clouds Appear Over Central Florida: What Are They?

ORLANDO, Fla. – Several communities that saw storms Tuesday night caught a glimpse of a rare and beautiful optical phenomenon.

These are known as pileus clouds with iridescence.

There are actually two things going on here.

The first was the formation of pileus cloud. These clouds form above a larger and growing cloud, such as a thunderstorm cumulonimbus cloud.

They form when strong updrafts force moist air above the growing cloud, causing it to condense into a wispy cap-like shape.

Typically, these clouds are short-lived as the main cloud that is rising consumes the pileus cloud.

The second part, the rainbow part, is cloud iridescence.

When sunlight is scattered by small water droplets or ice crystals in a thin, smooth cloud, it creates a diffraction pattern. In this situation, the diffraction was caused by a pileus cloud forming above a growing thunderstorm.

The diffraction (when light bends around the particles) creates a vibrant display of colors that appear to be a rainbow.

This phenomenon typically happens on hot, humid days when thunderstorms develop quickly. Additionally, the sun must be at a lower angle so that sunlight can travel through the atmosphere and illuminate the clouds.

Central Florida was dealing with record heat Tuesday, with storms firing around sunset.

Perfect conditions were met to catch not one, but two atmospheric phenomena at the same time.