Friday, February 6, 2015

A Naturalist's Thoughts on Winter Weather

February in the Mid-Atlantic can bring a wide range of weather - anything from sunny and balmy to freezing cold and snowy. This variability contributes to a wide range of winter precipitation. A wintry mix is a combination of rain, snow, freezing rain, and sleet.

Rain is liquid precipitation. The diameter of the droplets determines whether you have fog, mist, drizzle, light rain, moderate rain, heavy rain, excessive rain, or a cloudburst. Cloudburst droplets, although small at 2.85 mm in diameter, are over 200 times larger than fog droplets. (I wrote a previous post on this topic called How Big Are Raindrops?).

Snow consists of ice particles frozen into complex, six-sided patterns. Non-branching ice crystals - or diamond dust - form in the shapes of needles, columns, or plates.

Little Brother was very little when I took this photo of him playing in the snow.
He was very proud of his snowman!

Freezing Rain occurs when the atmosphere is warm enough for rain, but ground temperatures are 32 degrees F or lower. The rain freezes instantly when it hits the ground, coating everything in a layer of ice. Freezing drizzle is similar, but the individual drops of water are smaller. Freezing fog occurs when ice crystals are suspended in fog.

 I took this picture after an ice storm last winter. The rain froze the instant it hit the tree branches.

Sleet forms when snow melts in the atmosphere and then refreezes before it hits the ground. Sleet does not stick to objects the way freezing rain does.

This article (sans photographs) was first posted at the Audubon Naturalist Society. Come visit Woodend!

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