They are not. But then, there is the sailor's saying of “mackerel skies and mare tails make tall ships carry little sail.” So what's in it? Mare tails are, indeed, cirrus clouds made of ice crystals, at high altitude. read more
Mare tails are, indeed, cirrus clouds made of ice crystals, at high altitude. read more
Cirrus clouds are formed by a upward vertical motion of air in the upper half of the troposphere, as their structure suggest. Upward vertical motion in the upper troposphere is a sign of some unstability there. It could be as well caused by propagation of some strong vertical motion taking place bellow it (storm probably). read more
Since cirrus clouds arrive in advance of the frontal system or tropical cyclone, it indicates that weather conditions may soon deteriorate. While it indicates the arrival of precipitation (rain), cirrus clouds only produce fall streaks (falling ice crystals that evaporate before landing on the ground). read more
These are areas associated with convection, which unlike the synoptic scale flows is an efficient transport of moisture into the upper troposphere. This convective outflow will first be associated with the "anvil" top of the thunderstorm, but as it is advected at the upper levels can manifest as cirrus clouds. read more