A cloud species, from the Latin for 'hooked'. A cirrus cloud often shaped like a comma, and with a hook or tuft at the top.
Undersun:
A halo phenomenon produced by reflection of sunlight on ice crystals in clouds. It can be seen from aircraft or mountains and looks like a brilliant white spot on the clouds below the sun.
Undulatus:
Clouds in patches, sheets or layers, which show undulations like waves. Comes from the Latin for 'waved'.
Upbank Thaw:
A thaw, or marked rise in temperature at mountain level, which happens before the thaw takes place in a valley, sometimes many hours earlier.
Upslope Fog:
Fog which is formed on the windward slopes of high ground by the forced uplift of stable, moist air until saturation is reached by adiabatic expansion.
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Uncinus: