Mare's Tails

Photo by Craig Johnson

"Mare's tails and mackerel scales make tall ships carry low sails;" so says weather lore. In the early days of ocean going ships there were no weather forecasts. Ship's crews needed rely on their own observations and past experience to make decisions. Many times they were wrong but their forecasts were not always busts. The sky does give indications of what's coming next but given the complexity of our atmosphere sometimes similar clouds did not lead to the same result. That's because cloud altitudes and shapes are not always associated with the same weather outcome.

The scientific name for the above clouds is cirrus uncinus. Uncinus is from the Latin, meaning "curly hooks." These clouds are certainly have curly hooks! Most people know them by a different name; mare's tails. In this case the mare's tails remind us of the locks of hair on the lower hind legs of a girl horse. You can almost see the locks of hair blowing in the wind when you see cirrus uncinus. It is said that mare's tail clouds indicate approaching strong winds and suggesting ships should lower their sails because winds aloft could lower to the surface. Is it true? Not always but they are often associated with strong winds aloft that may eventually descend to the surface as a storm system gets closer.

You can try this out yourself to see if the weather lore is right. Watch the sky for mare's tails and then see observe your winds to see if they increase over time? If the winds increase how long did it take for it to become noticeable and how strong were they? Maybe the winds were already strong when you noticed the clouds. It is possible that the situation was already right for strong winds or there wasn't a storm coming after all. Or, as the weather lore states, "Mare's tails and mackerel scales make tall ships carry low sails!"

Do you want to read more about the science of high clouds? Link to a NASA web page on the subject by clicking here.