In the left-hand side of the depression the wind will back right round from south through east to north and northwest. In the rear of the depression on the left-hand side the wind blows from the northeast and then north, when the clouds begin to break and the weather to clear. When the depression has nearly passed away the wind in the rear draws round to the northwest, and gradually abates, and the weather becomes fine. Hence the saying:
Do business with men when the wind is in the northwest.
This bringing the finest weather is said to improve men’s tempers, as opposed to the neuralgic and rheumatic sensations felt in front of a depression.
WEDGE-SHAPED ISOBAR PROGNOSTICS.
Though the bulk of British weather is made up of cyclones and anticyclones, there are two other distributions of pressure marked out by wedge-shaped isobars and straight isobars respectively, which have never before been described, but which are associated with many well-known sayings. The chief interest in these prognostics consists in the contrasts which they present to cyclone prognostics, as in many cases they are associated with fine or dry weather, as opposed to the damp of an approaching depression. We shall first describe the prognostics which characterize the wedge-shaped area of high pressure that is frequently formed between a retreating and an advancing depression, as it is by far the most common.
All these prognostics owe their value to the fact that as the new depression comes on, rain may be expected. By reference to Fig. 3 it will be seen that in the rear of the retreating depression the weather is beautifully fine, of the sort of which we should say that it was “too fine to last,” or, if it lasted a whole day, we should call it a “pet day.”
Fig. 3.—Wedge-sharped Isobars.
An unseasonably fine day in spring is called a pet day in Scotland. The fate of pets they say awaits it, and they look for bad weather on the morrow.
During the day the sun is burning hot: