Page:Weather Facts and Predictions.djvu/10

 E. side the indications of the barometer precede the changes. Usually a rising or a high barometer indicates less wind or rain, that is, fair weather. A falling or a low barometer more wind or rain, or both, that is, bad weather.

In temperate climates, towards the higher latitudes, the range of the barometer amounts to about 2½ inches, that is to say, it may vary from about 30.8 in. to less than 28.1 in. on extraordinary occasions. The usual range, however, is much less, say from 30⋅5 in. to 28.75 in. In the tropics the minimum of depression may be put at 27.7 in.

A fall of half a tenth, or still more of a whole tenth, in one hour, is a sure indication that a storm is coming.

If after remaining steady at about 29.9 in. the barometer rises, and the temperature falls, the air at the same time becoming more dry, then N.W., N., or N.E. wind, or less wind may be expected.

If when it falls the temperature rises, and the air becomes more charged with moisture; then wind, rain (or snow) may be expected from the S.E., S., or S.W.

Exceptions to these rules occur when a Northerly wind with wet (rain, snow, or thunderstorm), is impending, previous to which the barometer often rises (but only on account of the direction of the coming wind), and thus deceives those who from the rising are led to look for fair weather.

The barometer standing at about, say 29.5 in., a rise foretells less wind or a change towards the N. or less wet.