National Geographic : 1892 Mar 26
86 General A. W. Greely-Geography of the Air. status. Of meteorology, however, using this term as especially applying to weather and not to climate, which will be referred to later, it may fairly be said that the generalizations are too indefinite in terms and too scanty in number, the ascertained and acknowledged facts too insufficient as well as too disjointed in their relations, to form the indispensable work of fundamental principles whereon is to be woven the regular, graceful curves which nature ever presents to us under the magic wand as waved by the specialist in any science. The term " science " carries with it in a degree the idea of prevision, so that exemplifications of its principles shall always find expression in foreseen results, whose ultimate variations should not exceed certain narrow limits. Abercrombie and the writer have published, almost simul taneously, the latest works in English on the weather. My own opinions as to the status of this department of nature were clearly put in " American Weather," 1888. To quote: "All skilled meteorologists realize how comparatively local are weather conditions and how impossible it is, at times, to make predictions for a definite period with any feeling of certainty. * * * It is evident that fair-weather conditions are those which are most persistent [i. e., they partake more of climatic conditions than of weather] and from the pre diction of which the highest percentages of accuracy will be obtained." Professor Marvin, a careful, conscientious official, whose duty has included the examination and verification of forecasts, after three years of study, says (referring to verification-percentages not being strictly comparable) in confirmation: " The reasons for. this are principally because of the much greater difficulty of successfully forecasting rainy and unsettled than fair weather, together with the seasonal spasmodic variations in their respect ive occurrences." His illustrations make clear what has been believed by all close observers, namely, that high percentages and satisfactory forecasts are attendant on the persistency of climatic or permanent conditions (such as no summer rain in California) when unbroken by the violent and marked changes which distinguish weather from climate. It is safe to say that the percentage of successful forecasts of rain twenty-four hours in advance is not one-half, and probably not more than one-third, so successful as forecasts of fine, clear weather for the same period.
1892 May 15
1892 Feb 19