Green Comet

“Red sky in the morning, sailor take warning. Red sky at night, sailor’s delight.” It’s a variation of an old proverb that seems to have a local version wherever you go. And it has a scientific explanation. It’s based on the fact that, in the regions where most of the old proverb makers lived, the general circulation of the atmosphere is from west to east. The high- and low-pressure systems that bring our alternating good and bad weather move eastward with the atmosphere.

Air sinks in a high pressure system; that’s why there’s more pressure. The sinking air traps dust. Air rises in a low pressure system, flushing the dust out of the lower atmosphere. The different amounts of dust cause more or less redness in sunrises and sunsets. A dust-reddened sunrise indicates that the higher air pressure is to the east, meaning it’s going away with the westerlies, taking the good weather with it. “Sailor take warning.” Red sunsets mean the good weather is to the west of us, coming closer with the prevailing winds. “Sailor’s delight.”

“Mackerel scales and mares’ tails make lofty ships carry low sails.” This is another adage that has an equally good explanation. Clouds in the form of mackerel scales and horses’ tails are the high forerunners of weather systems. The high clouds tend to arrive first because the winds are typically stronger at their altitude. They can indicate that soon we will see lower clouds and possibly bad weather. The kind where you don’t want all your sails in the wind.

There are many similar sayings for haloes around the Sun and Moon and other meteorological phenomena, all used by people trying to live with the weather. Today we use other methods of measurement, but they are largely looking at the same things that produced the effects described in the old proverbs. The impulse to understand the weather was always there, but today we apply a system of science and technology that goes beyond appearances.

On radio and television and in newspapers we get continual updates and revised forecasts many times a day. On the internet we have access to the same maps, charts and satellite images. Here are some sites for weather lore, cloud pictures and a satellite image.

Good sailing.

rjb