What is white ice frost?

What is white ice frost? White ice frost is a type of solid ice that forms directly from water vapor found in the air. White frost forms when the humidity is above 90% and the temperature is below 18 degrees Fahrenheit.

White ice frost grows against the wind, since the facing winds have higher humidity than leeward air. The wind must be light or the delicate icy structures become broken. The structures have big, interlocking, needle-like crystals. This phenomenon occurs very rarely. Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) to ice (a solid) as the water vapor reaches the freezing point. In temperate climates, it most commonly appears on surfaces near the ground as fragile white crystals; in cold climates, it occurs in a greater variety of forms. The propagation of crystal formation occurs by the process of nucleation.

White frost is an intermediate stage between actual hoar frost and rime, which is sometimes confused for either or both of these elements.

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