Page:Handbook of Meteorology.djvu/169

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marvelously good. With intelligent study of wind, clouds, and moisture, one should be able to forecast most ordinary weather changes from eight to twelve hours in advance, without the aid of barometer or weather map. This does not apply to such local disturbances as tornadoes, thunder-storms and hail, nor to such conditions as ice storms and sleet.

Throughout the greater part of the United States easterly winds indicate the approach of a cyclonic storm. If the wind is from the south or the southeast, the storm is probably approaching along a path to the north of the observer; if the wind has settled to a quarter between east and northeast, the track is somewhere south of the observer; if the wind is due east, the observer is probably in or near the track of the storm center.

If the sky remains clear with an easterly wind the rain area is likely to pass some distance from the observer; but if the sky becomes gray, and then white, and the air perceptibly damper, rain is not likely to be far away. When cirro-stratus clouds appear in the easterly sky, rain or snow is pretty certain at hand within a few hours.

The position of the storm center may be determined by watching the wind closely and noting any change that may occur. Standing with the back to the wind the area of low pressure is on the left hand, and the area of high pressure on the right hand. During the passage of the storm, if the wind shifts from the east through north to northwest—that is, if it “backs in”—the cyclone center is passing to the south of the observer. If it veers through the south to the west or the northwest, the storm center is passing north of the observer.

The cooperative observer can do much to aid in establishing definite facts on which predictions may be made. Among them and of first importance is establishment of the direction of rain-winds. These, as has been shown, are easterly winds, but conditions of topography may change the real direction to one that is apparent. The apparent direction should be established for each month in the year. In every community there are weather-wise people who possess valuable information that they have not recorded. Such information should be considered carefully and accepted or rejected as the case may be.

The number of days in each month on which o.oi inch or more of rain has fallen should be. noted, tabulated, and com-