Ask A Scientist© Weather Archive

name         Sara
status       student
age          20s

Question -   What is the actual shape of a snowflake?

Sara,

Single, complete snowflakes are hexagonal; they have 8 branches.
They come in many sizes and in a beautiful array of crystalline
varieties.  Often you don't see single crystals when it snows,
as it is common for the crystals to collide as they fall,
breaking into pieces or combining into little snowballs of
partially melted snow.

David Cook
Meteorologist
Argonne National Laboratory
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In a recent reply to your question about snowflakes,
I mistakenly said that snowflakes have 8 branches.

OOPS!  Everyone knows that snowflakes have 6 branches.
The branches tend to expand from a hexagonal plate
which normally forms on a particle (soil, salt, pollutant)
in supercooled air.

I hope that someone caught my mistake, but just in
case someone didn't, I wanted to let you know.

David Cook
meteorologist
Argonne National Laboratory
=========================================================
Krista,

Temperature and water vapor content affect snowflake shapes.
If the temperature is at freezing, snowflake branches
tend to melt, ending up looking rounded or they combine into
little balls called graupel.  If it is quite cold where the
flakes form and fall, they will keep their classic branched
snowflake shape and not combine with other flakes.  The more
water vapor there is in the air and the further they have to
fall from the cloud, the better developed the snowflake
branches are.

David R. Cook
Atmospheric Section
Environmental Research Division
Argonne National Laboratory
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