In one of his better compositions, William Wordsworth includes lines which might be applied to successive elements of the nightly weather forecast.
Each in solemn order followed each,
With something of a lofty utterance drest;
Choice words, and measured phrase, above the reach
Of ordinary men.
It is not, of course, that the words one might complain of are intrinsically difficult to understand; it is just that their meaning in their context may not always be entirely clear.
Consider the wind, for example, since it has figured rather prominently of late.
Some descriptive terms have acquired over the years an accepted, somewhat intuitive, meaning - words like "strong", "moderate", "fresh" or "light".
When is it desirable to be a little more precise, however, the wind is often specified in miles per hour, or perhaps kilometres per hour or even metres per second. All these mean precisely what they say: when the wind is described as blowing at 20 m.p.h., for example, it means that the air travels 20 miles in every 60 minutes.
Television weather forecasters are helped by graphics. Some may show the wind speed plotted on a little circle, with an arrow to indicate the direction from which, or perhaps towards which, the breeze will blow.
Other are more adventurous. They may depict the wind as a broad river of arrows sweeping along in the general direction of the flow of air, with thick arrows telling of a gale and slender shafts predicting a gentle breeze.
Then, after a storm, the newspapers and other media often tell us that winds of 80, 90 or even 100 m.p.h. have occurred at various points around the country. Yet winds of this strength are never displayed on the nightly weather charts on television. The confusion arises because a distinction is not always made between the average strength of the wind, given in the weather forecast, and its speed in gusts.
The wind is never steady. Even over a period of a few seconds, it is constantly rising and falling, increasing and decreasing in strength, because of its interaction with the rough surface of the Earth.
Because of their clear passage over water, winds straight from the sea tend to have a relatively low gustiness factor. For an average wind of, say, 20 m.p.h., the instantaneous speed may vary from a maximum speed of about 25 m.p.h. in gusts to about 15 m.p.h. in lulls.
However, over hilly country the gustiness factor is much greater: the difference between the maximum and minimum speed over a few minutes is often comparable to the average wind speed itself.