Why do snowflakes form patterns

Atmospheric conditions for freezing rain: Snowflakes form high in the atmosphere. If they melt completely on the way down, then land on a cold Earth, the result will be freezing rain. If the snowflakes pass through a layer of warm air that is thick enough to melt them completely, then land on a cold Earth surface, the result could be freezing rain. Meteorologists have a challenging job. If they forecast snow, they need to determine when a moisture-laden air mass will pass over an area and if the temperature high at the snowflake-forming elevation will be below freezing.

They also need to determine if the temperatures at lower elevations will allow the snowflake to fall to the ground. Finally, they need to know the conditions on the ground to determine if the snow will accumulate or melt. If you think this is interesting and you like to be challenged, then you might make a great meteorologist. How Do Snowflakes Form? The life of a snowflake begins high in Earth's atmosphere, and if the snowflake is very lucky it might reach the ground.

Article by: Hobart M. Find Other Topics on Geology. Maps Volcanoes World Maps. Igneous and Volcanic Features. Geology Dictionary. In ice crystals the shape they take mirrors the shape of the molecules forming the crystal. The crystal structure of frozen ice is a six-sided shape. Therefore an icy facet is six-sided as well. That is where the symmetry in a snowflake comes from. The second way to grow a snowflake is to form branches. Not surprisingly, this is what creates those beautiful tree-like structures.

Branches form because water vapor will condense on the first thing it touches. The process repeats itself and a branch is formed! While the snowflake generally starts as a prism with six facets, its growth can switch back and forth between creating facets and forming branches.

And both processes can occur at the same time. Water molecules simply arrange themselves to fit the spaces and maintain symmetry; in this way, the different arms of the snowflake are formed. Howard T. Evans, Jr. Geological Survey, adds a few details: Snowflakes are mysterious things. Their fundamental form derives from the arrangement of the water molecules in the ice crystal.

When a liquid freezes, the molecules tend to settle in the lowest-energy state, and that almost always involves some form of symmetry. The higher the symmetry, the more stable the crystal is. Water molecules floating freely in a vapor begin to arrange themselves into a crystalline solid when the temperature drops below freezing. The two hydrogen atoms of the molecules tend to attract neighboring water molecules. When the temperature thermal motion is low enough, the molecules link together to form a solid, open framework that has a strict hexagonal symmetry.

But why are snowflake shapes so elaborate? Many appear to be two-dimensional works of art. Others look like a matted cluster of fraying ice strands.

Most come as individuals, although some can fall as multi-flake clumps. What all have in common is their source: clouds that usually hover at least a kilometer 0. In winter, the air up there can be very cold — and will get chillier the higher you go. To form snowflakes, those clouds need to be below freezing. But not too cold. Snowflakes form from the moisture in a cloud.

So there has to be a balance. Snow can form in cooler environments, but the colder it gets, the less moisture will be available to make a snowflake. That means there is more water in the air than would normally be possible. The relative humidity can reach percent during supersaturation.

That means there is 1 percent more water in the air than it should be able to hold. When there is too much liquid water in the air, a cloud will try to rid itself of the excess.

Some of that excess can flash freeze into crystals, which then lazily meander to the ground. One more thing is needed to turn cloud moisture into a flake. Scientists call it a nucleus NOO-klee-uhs. Even when the air temperature is well below freezing, water droplets will remain liquid — at least until they have a solid object onto which they can attach. Usually, that will be something like a pollen grain, dust particle or some other airborne bit.