MEMPHIS, Tenn. (WMC) - We are used to scraping frost off our cars, or seeing it glisten on a cold morning across a grassy surface, but have you ever seen a very intense form of frost that looks like nothing you have seen before?
Well in this episode of the Breakdown, we will explain why this jacked-up frost, might just be a term called hoarfrost.
According to the National Weather Service office in Riverton, Wyoming, the Old English dictionary (c. 1290) defines hoarfrost as “expressing the resemblance of white feathers of frost to and old man’s beard.”
First off, let’s talk about how frost forms. Water vapor, which is just the gaseous form of water, is in the air over a cold ground with a surface dew point at least 32 degrees.
As the water vapor particles contact the subfreezing surface, like grass or cars, they jump directly from a gaseous state to a solid. This process is known as deposition, leading to the coating of tiny ice crystals.
While we are used to seeing normal frost in the Mid-South, when there is much more of a moist air mass in place. This usually can happen in late fall, winter or even early spring, or one or more days in a row of freezing fog, is a perfect recipe for this to form.
With the extra moisture in the atmosphere, the interlocking crystal patterns of frost before more intricate and larger, building to greater depths on those tree branches, signs, fences and anything else. This is considered hoarfrost.
If there is a light wind, then the hoarfrost will accumulate on the downwind side of the object.
To wrap it up, a hoarfrost is just a frost with a bit more moisture in the atmosphere for the frost to form at greater structures and lengths.