Scientists unsure if there is an upper limit to snowflake size

Dec. 10 (UPI) -- As many children on the East Coast taste a snowflake for the first time this season, kids and parents may be curious about the fluffy crystals.

Why don't they look like the ones on the Christmas tree? And is it true that no two snowflakes are alike?

Megan Skrip, a researcher and science communicator at North Carolina State University, wanted to know how big snow flakes can get. The largest snowflake ever found measured 15 inches wide and 8 inches long, according to a recent blog post by Skrip, who cited a trivia-filled page-a-day calendar.

The snowflake was reportedly found in Fort Keogh, Montana, in 1887, but according to snowflake expert Sandra Yuter, the snowflake wasn't actually a snowflake.

The larger natural snowflakes -- over 1 inch or more -- are actually jumbles of individual ice crystals called aggregates," Yuter, a researcher at N.C. State, told UPI in an email. "Temperatures slightly colder than freezing are conducive to aggregate snow formation."

The size and shape of each a snowflake is influenced by atmospheric factors, including temperature and humidity.

"The exact shape of the final snow crystal is determined by the precise path it took through the clouds," Kenneth Libbrecht, a professor of physics and department chairman at the California Institute of Technology, explains on his website dedicated to snowflakes. "But the six arms all took the same path, and so each experienced the same changes at the same times. Thus the six arms grow in synchrony, yielding a complex, yet symmetrical shape. And since no two snow crystals follow the exact same path through the clouds as they fall, no two look exactly alike."

While it's true that no two snowflakes are alike, Libbrecht can grow snow crystals that are very similar. He shares pictures of his "identical twin" snowflakes on his website.

Though Libbrecht and other scientists can study the growth of snow crystals by growing them under microscopes in the lab, researchers can also study the real thing.

"Today we have automated cameras like the Multi-Angle Snowflake Camera that take research quality pictures of snowflakes in free fall," Yuter said. "With the Multi-Angle Snowflake Camera, we can see what the 3D snow geometry looks like as it falls, which is highly relevant especially for research that relates remote sensing of snowfall from weather radar and satellites to snowfall rates."

As to whether there's an upper limit to snowflake size -- or more accurately, snowflake aggregate size -- scientists aren't sure.

Yuter told Skrip that really big aggregates likely form in snow clouds, but atmospheric winds keep them from ever reaching the ground.