November 30 2020

Did you see a ring around the moon last night? I got many messages and photos about it, some saying they’ve never seen it before.  The good news, this is more common than you might have guessed. This is the season for them, and they can actually help you forecast the weather.

Lunar Halo 

This first photo is from Jennifer Anderson. She wrote: “I’ve never seen a ring that big around the moon. Is there a scientific term or name for it?”

The term is a lunar halo, which is the ring of light around the moon. A full moon and approaching storm were the perfect combination to make this happen.

 

 

This photo from Lindsey Ellison came with this note: “Almost heavenly!! I have never seen this in all of my 45 years.”

When you see what causes it, you will be looking and I promise will see more. There are more photos below as well.

 

What Caused This Lunar Halo?

The short version, moon light through ice crystals refracted the light in the atmosphere.

• We have a full moon, which gives us bright light at night.
• We have a storm today, which was preceded by high thin clouds last night.
• Those clouds were made of ice crystals that have a 60º angle to them.   The refraction bends the light 22º

 

The Science

Ice Crystals have fixed, rigid angles. The transparency lets the light pass through, but it slows down and bends on the way (refraction).

 

 

The Sky Set Up

This is more common in the winter season because:

1. Larger storms often send the initial high thin clouds farther away. This can be 12 hours or up to 2 days before precipitation arrives.
2. Longer nights allow more time to view the night sky.
3. A moon phase larger than 1/4 and up to full will provide enough light to provide this effect.

 

The net result in the sky is a ring of light that is 22º

 

 

Morning Weather Forecast: Rain Today and Snow Showers Tomorrow 

 

More Photos

From Bel Air, Maryland this was from Lori Fioramonti Decher.

 

 

Abigail Kait shared this photo her husband took while walking their dog.

“He says folklore hints at snow coming. Have you seen this happen or heard of it??”

The answer is yes!  This is called a Lunar Halo, and the folklore is correct. However, it depends on the temperature.  It will foretell of snow or rain in the next day or two.

 

 

This photo from Jennifer Weinreich Stairs provides a great contrast with the line of trees.