Page:Weather Facts and Predictions.djvu/14

 presaged weather will last; and, conversely, the shorter the warning the less time will the coming wind or weather continue. In other words—

Sometimes severe weather from the S., which will not last long, may cause no great fall, because a northerly wind is impending; and at times the barometer may fall with northerly winds and fine weather apparently against the common rules, because continued southerly wind is impending. Changes thus occurring may mislead, unless the possibility of their occurring is borne in mind.

If the barometer at any place oscillates violently, and the air there remains calm, it is certain there is disturbance going on some- where in a lateral direction.

At times, in winter, the southerly current prevails over a large area, and the barometer is low and the weather mild. Under these circumstances it may be presumed that severe weather with a high barometer is prevailing somewhere in the neighbourhood. It is possible that this cold and condensed air may force its way into the warm and rarified air in its vicinity, and cause the barometer there to rise rapidly.

Comparing rainy weather with snowy weather, during the course of one revolution of the wind the barometer will fall lower during rain than during snow.

If the barometer rises very quickly, it is an indication that the polar and equatorial currents have met and are in conflict. A severe storm