Windswept_ The Story of Wind and Weather - Marq de Villiers [59]
From a wind point of view, the interesting thing about the great English storm—a point made repeatedly by Defoe in his first chapter—was not so much the damage it caused, or what had happened, but that no one had even guessed it would happen. Put another way, everyone knew what had happened, but no one knew why.
It's not that people weren't interested, and weren't trying. Ancient weather lore was derived from careful observation of natural phenomena like clouds and by watching animal and insect behavior. The Farmer's Almanac notion that animals put on heavy coats before a particularly bad winter is not true; nor do squirrels increase their larders when severe winters are ahead; nor do frosts happen more often at full moon. But plenty of other signals are true, at least much of the time. For example, exposed seaweed will indeed swell ahead of bad weather, an effect that has to do with dropping atmospheric pressure.
Mariners particularly, whose safety depended on surviving storms, developed a whole litany of signals to foretell storms. Columbus, who in effect issued the world's first-ever hurricane prediction in 1502, based his anxiety on scudding wisps of cirrus clouds and on long swells from the southeast, signals of a storm that had nearly wrecked his expedition on his first voyage. Don Nicolas de Ovando, the new governor of the Spanish colony, ignored Columbus's warning, and ended up losing twenty-one ships to the hurricane that ensued.3
Columbus, like many a sailor before him and after him, recognized many different cloud types and shapes. It wasn't until 1803, though, that clouds were given their own taxonomy, when they were classified by Luke Howard. He arranged them into three general types: cirrus (curl), cumulus (heap), and stratus (layer). Other types of clouds, such as nimbus (rain clouds), were variations on these three basic types. Modern meteorology also classifies clouds by height—the prefix cirro denotes the highest clouds, 3.6 miles or higher; alto is the prefix given to clouds between 1.2 miles and 3.6 miles; clouds below that have no special prefix.4 High clouds are usually made up of ice crystals, medium clouds of water droplets and ice crystals, and low clouds only rarely contain ice. Clouds, if you can learn to read them, can be accurate, if occasionally ambiguous, weather predictors. Light, scattered clouds alone in a clear sky usually mean strong winds. Clouds lowering and thickening always bring deteriorating weather, while clouds increasing in numbers, moving rapidly across the sky, are often a warning of really bad things to come. In the midlatitudes, scattered clouds with blue skies to the west mean predictably fair weather.
In short order sailors learned to watch for signs of a tropical cyclone. The first signal was a broad trail of cirrus clouds, with heavy showers of rain (it is now known that these travel 300 to 350 miles, ahead of a storm). A sign that a storm was imminent was when that same cirrus departed rapidly, scattering in all directions, followed by a thin, watery veil that pervaded the air. By the time the next sign appeared—an ominous wall of cumulonimbus with layers going in different directions—it was too late to take evasive action, and the gear was lashed to the decks or stowed below, and storm-sails hoisted.
This scattering cloud is a true signal, known to sailors everywhere. Sebastian Smith quotes a fisherman in the Mediterranean port of Carro, who told him the trick of predicting a mistral: "There may well be no indications of bad weather. The air becomes beautifully clear, but then you get clouds like little balls. Clouds like plates, or some say cigars, are another sign. But stay alert, when these balls start to explode and scatter, the mistral will soon be upon you."5