Over a thousand years ago, in the middle of the ninth century, Pope Nicholas I made a significant contribution to meteorology. It was he who decreed that the figure of a cock should surmount the topmost pinnacle of every abbey, cathedral and parish church in Christendom.
The emblem was intended as a reminder of St Peter's weakness. Having denied the Lord three times, Peter heard the crowing of a cock, and was reminded of his master's short-range forecast of the night before, whereupon, we are told, the repentant apostle "went out and wept bitterly". The Papal ordinance was harnessed to another purpose by mediaeval architects who found it useful to have the "weathercock" display the wind's direction.
But weathercocks are superseded, and nowadays there are many different ways to tell the story of the wind. On television, for example, the wind speed is often shown as a Beaufort force, or indicated by a number giving miles or kilometres per hour; the number is plotted on a little circle, and an arrow then indicates the direction from which - or perhaps towards which - the wind may blow.
In recent times, computers have made it possible to devise more stylish, more dynamic ways of getting across this simple message. Some television channels, for example, portray the wind as a broad river of arrows, sweeping along in the general direction of the flow of air; the arrow widths and lengths are chosen to give a visual impression of the wind regime.
Sometimes the colour of the arrows - red or blue perhaps - may give an indication of the temperature. It means, of course that you cannot put a number on the wind or warmth, but for some viewers it may communicate the "feel" effectively, and make the weather message easier to understand.
Meteorologists prefer to look at isobars - even when relaxed at home and watching television. Isobars, you will recall, are the lines on a weather chart drawn through points of equal barometric pressure. They outline the pressure pattern in much the same way as the contours on an ordnance survey map display the ups and downs of the terrain.
The wind direction at any point on the weather chart coincides, more or less, with the direction of the isobars. The air flows along them with low pressure to the left, sweeping anti-clockwise around areas of low pressure.
The speed of the wind is "inversely proportional" to the distance apart of the isobars - a complicated way of saying that the closer they are together, the stronger blows the wind, and vice-versa.