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 A LONG-RANGE TEMPERATURE FORECAST 



By C G. ABBOT 



Research Associate, Smithsonian Institution 



GENERAL COMMENTS 



I quote the opening paragraph of my recent paper "A Long-Range 

 Forecast of United States Precipitation" x : "A hidden family of 

 harmonic regular periods exists in weather. The periodic members of 

 this family persist with unchanged lengths for scores of years. By 

 determining their average forms and amplitudes for intervals of a 

 thousand months, successful forecasts may be made for years to come ; 

 or backcasts may be made for former years and compared to former 

 events. Agreement of such backcasts with the records warrants con- 

 fidence in future forecasts." 



In the publication cited correlation coefficients ranging between + 52 

 and +69 percent were found over the interval 1950-58 between pre- 

 diction and observation. Positive coefficients of correlation, as I will 

 show, also subsist between temperature forecasts and events for the 

 same interval. Examples appear herein as figures 1, 2, 3. 



While very nearly normal weather must obviously average closer to 

 the normal values than to my forecasts, the case is quite different for 

 extremes of weather. Extremes in precipitation range from 50 to 200 

 percent away from the normals. It is to be able to anticipate weather 

 of this unusual kind that good forecasts are financially valuable. As an 

 example I give the following computations based on tables 10 and 14 

 of Publication 4390: 



Cincinnati results from table 10 



From 108 months, 1950-58, mean departures from normal, 29% 



from forecast, 27% 

 From 56 months within 25% of normal, 



from forecast, 26% 

 From 52 months over 25% from normal, 



from forecast, 27% 

 From 20 months over 48% from normal, 



from forecast, 31% 



1 Smithsonian Misc. Coll., vol. 139, No. 9, Publ. 4390, Mar. 23, i960. 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 143, NO. 5 



I 



