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In the list and the examples given, colour is associated with changes in the weather. It ranges from the white of cirro-cumulus to the dark grey of nimbo-stratus. The association is shown in further instances of sky colours, the first of which occurs in the old saying:
Red sky at night, shepherd's delight
Red sky in the morning, shepherd's warning.
It has been estimated that this is true about three times out of five. The second illustration adds another colour to the range: yellow. A watery yellow sunset is a sign of coming rain; a bright yellow sunset is a token of an approaching high wind. Again, a golden ring round the moon is a warning that a storm is on the way. In the last place, there is the rainbow. This multi-coloured arc appears opposite to the sun, and is formed by refraction and reflection of its light through falling raindrops. If the sun is in the east, and the rainbow is in the west and a west wind is blowing, then rain is moving towards the observer. If the sun is in the west and the rainbow is in the east and a west wind is blowing, then rain is moving away from the observer.
Clouds then are an index of weather changes; and so is the wind, which we now consider.
Wind
The subject is of immediate interest to the kite flyer, for the
wind is in turn both his friend and his foe. He cannot alter this fact, but he may gain some knowledge of these different moods which may stand him in good stead. Under this heading brief comment will be made upon each of the following items: first, wind and weather; second, estimating wind direction; and third, estimating wind speed.
Wind and Weather
As far as the British area is concerned, a general statement may be made: south-westerly winds are wet winds; north-easterly winds are dry winds. The south-westerly winds which have travelled hundreds of miles across the Atlantic have taken up a great amount of moisture on the way. When they encounter the main highlands of the area, they are forced to rise and in so doing the greater part of the moisture is squeezed out as rain. On the other hand, north-easterly winds when they prevail for a time, are usually a sign of an anticyclone over the North Sea, or even farther north-east, and anticyclones are associated with spells of fine weather.
(Additional notes on depressions and anticyclones are given at the end of this chapter.)
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