What caused these gorgeous ice formations on cars?

Frozen Fractals all around.

What caused these gorgeous ice formations on cars?
From Joe Lacy III (Source: Joe Lacy III)

RICHMOND, Va. (WWBT) - We got a LOT of rain Wednesday 12/16/2020. And it was a COLD, too. With a temperature in the 30s, the water wasn’t frozen, but it was close.

Then, when temperatures dropped BELOW Freezing early Thursday morning some people awoke to an icy, and beautiful sight.

Check out these pictures from Joe Lacy III

From Joe Lacy III
From Joe Lacy III (Source: Joe Lacy III)

No, Joe did not get an expensive custom paint job.

From Joe Lacy III
From Joe Lacy III (Source: Joe Lacy III)
From Joe Lacy III
From Joe Lacy III (Source: Joe Lacy III)

And this picture from Kathryn Bott who is a first grade teacher.

She asks, “I was wondering if you could help my class solve a weather mystery. What causes ice to create different patterns on surfaces? Is there a scientific reason behind the intricate patterns that are created? We learned about observing patterns in nature last year in kindergarten and have been studying weather this year now in first grade. We would love any insight that you may have. Thank you!

Picture from Kathryn Bott
Picture from Kathryn Bott (Source: Kathryn Bott)

I’ll give it a shot. I don’t think it was frost at all. I think it’s just “ice.”

Frost forms when moisture condenses out of the air directly onto a surface. This happens when the air temperatures dips to the dew point AND it’s below freezing. When this happens, the frost coats surfaces. Most of the time it’s dull.

When conditions are just right, HOAR Frost forms. We had a great example of hoar frost back in January. I posted a picture on my facebook page and many of you added to the conversation.

“My deck grew “fur” this morning!” Tonia Threlkeld took this picture yesterday morning in Moseley (Chesterfield). (It’s called HOAR FROST and it’s gorgeous 🥰)

Posted by Andrew Freiden NBC12 on Thursday, January 9, 2020

In the case of Thursday morning, ice crystals formed gorgeous, repeating patterns as the liquid water crystallized into ice. I don’t think it was a true “frost” at all. In my opinion, It was just a sheet of liquid water freezing.

In the right circumstances, that can be an amazing design-- like in the pictures Kathryn and Joe sent me. I’m FAR from an expert on how ice crystals form (and there actually aren’t a lot of experts out there studying frost and ice) but I do know that like snow, no two ice crystals are the same. And that the environmental factors in place on the car’s surface probably DIDN’T CHANGE as the crystals were forming. If they did, the crystals wouldn’t have had a repeating pattern.

This leads me to believe the crystals grew very quickly. If the air slightly warmed, or changed humidity, or the wind blew as the freezing was happening, the crystal pattern would have changed.

Those exact patterns will never be exactly repeated again, but with some luck, we’ll get to see something similar before the winter is up!

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