Mares’ tails over a national forest


Janet Ealem
Location: Shasta-Trinity National Forest, CA
Date: 7 July 2014

At heights more than 20,000 ft (6,000 m) above the surface, cirrus clouds are made up primarily of ice crystals. These small, light, delicate crystals are easily carried by the winds, which tend to be stronger the higher you go up in the atmosphere. The winds can twist, spread, and generally distort the shape of the cirrus clouds as the wind speed and direction vary between different levels. The ends of these clouds can appear to curl as the crystals fall into different winds below, giving them the name Cirrus uncinus, meaning “curly hooks.” These clouds are also commonly given the nickname Mares’ tails, which you can see the resemblance below.


Did you know that the nickname “mares’ tail” is also given to the invasive plant Equisetum  (also referred to as horsetail)? I can see the resemblance. I enjoy the similar patterns that appear in nature. 🙂


Back to the cirrus clouds, it sure looked like a pleasant day to be in the national park. These clouds typically indicate fair weather, although of they start to cover more of the sky and thicken, it can be a sign of increasing moisture ahead of a warm front and possibly less pleasant weather in the next day or so.


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