Page:Weather Facts and Predictions.djvu/11

 The barometer standing at about, say 29in., the first rising usually precedes high winds from the N.W., N., or N.E., after which, if it still rises, and the temperature falls, improved weather may be looked for. But if the temperature remains high, probably the wind will "back" (shift against the sun's course) and more S. or S.W. wind will follow, especially if the rise has been sudden.

The most violent gales, especially from the N., happen soon after the barometer first rises from a very low point, or if the wind rises gradually, at some time afterwards, although the barometer continues to rise.

A simultaneous rise of pressure and temperature is a sure sign of fine weather. Indications of approaching change of weather are shown by the movement of the mercury rather than by its absolute height or depression. Nevertheless, a height of more than 30.0in. is indicative of fine weather, and moderate winds, except from E. to N. occasionally, when it may blow strongly.

A rapid rise in the barometer indicates unsettled weather, as also does alternate rising and falling.

A gradual rise, or a steady barometer accompanied by dryness, foretells fine weather likely to endure for some time.

A rapid and considerable fall indicates heavy rains with general foul weather.

If fair weather continues for several days, during which the barometer continuously falls, a long succession of foul weather may be expected.

Similarly, if during the continuance of foul