Jacques Wardlaw Redway

“ To the trained observer, or to the observer who has gained wisdom by experience, it is an instrument of the highest value. To be serviceable in forecasting weather conditions it must be watched—not casually but systematically. The experience that comes from intelligent study of pressure changes will enable an observer to command most gratifying results.
General Pressure Indications.—As a rule, pressure changes should not be considered by themselves; they should be studied in conjunction with changes in temperature, humidity and wind direction. ”

“ A rise from a very low pressure indicates wind and clearing weather—the more rapid the rise, the stronger the wind. Rapid changes in pressure indicate early and marked changes in the weather.
A sudden rise in pressure indicates as great a change as a sudden fall.
The wind is apt to blow hardest when, after having been very low, the barometer begins to rise. ”

“ Ordinarily, the air which may be at the dewpoint at daylight becomes relatively dry at midday because its higher temperature gives it what is popularly termed “a greater capacity for moisture.” But if the relative humidity remains high in the middle of the day it is evident that the absolute humidity has increased, and unsettled weather may be expected. ”

“ Straight south winds along the Atlantic and Gulf Coasts are apt to bring unsettled weather, inasmuch as the south wind blows from the sea, it usually brings warm air and excessively humid weather. Occasionally it brings storm conditions. ”

“ While the former condition in itself does not indicate an approaching storm, it is instructive in connection with other local indications.
A sky overcast with high clouds does not indicate stormy conditions if the clouds remain high. If the pressure falls and the clouds lower, stormy weather may be expected.
Rapidly increasing cumulus clouds indicate thunder-storms. A thunder-head or high cauliflower top to a cumulus cloud denotes a rapid updraught, which in itself is the beginning of a thunder-storm. ”

“ West winds are dry winds; in the eastern half of the United States they are apt to be dust-laden also. In midsummer they blow many miles over sun-heated ground and they are therefore apt to be hot winds. ”

“ Barometer and Wind Indications.—When pressure and wind-direction are both considered and interpreted according to their mutual relations, local forecasts can be made with a much greater degree of certainty. During the colder months, throughout the United States, the western highlands excepted, precipitation begins with falling pressure. In the summer months, and in the western highlands it is apt to begin with the rising barometer. ”

“ But if a change is not forecast, or if the words ”not much change,” ”slight change,” ”continued warm,” (or cool) , or ”stationary temperature” are used, a definite number of degrees (6 in summer and 10 in winter) is required to vitiate the forecast. Modifying words, “slightly,” “much,” “probably,” etc., do not relieve the forecaster of the failure of his verification.
Time of Occurrence.— The forecasts most generally sent out for publication are based on the 8:00 a.m. ”

“ Southeast winds are rain winds along the entire coast and much of the interior of the United States, for the greater part of the year. The time varies from twelve to eighteen hours in winter and from eighteen to thirty-six hours in summer. ”