Cirrus uncinus

From Glossary of Meteorology

cirrus uncinus

A species of cirrus without gray parts, the elements of which are often in the form of a comma, topped with either a hook or a tuft that is not rounded.

The species uncinus is unique to the genus cirrus. The hook takes the shape of a reverse question mark under positive wind shear (wind increasing with height) conditions and the shape of a question mark under negative wind shear.

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