56 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. jy 



The mean results of the forecasts for three, four, and five days 

 ahead are given in table 17, zero day being in each case the day for 

 which the forecasts were made. 



Table 17. — Verification of Temperature Forecasts Made for New York City for the Year 

 December 1, 1923 to December 1, 1924- — Mean Maximum Temperatures. 



Fore- 

 cast 



Above Normal 



Normal 



Below Normal 



Days 



— 1 



3 days 



ahead 



4 days 



ahead 



5 days 



ahead 



+ L86 +2.45 +1.62 +1.20 +1.15 

 +0.26'+0.71 +0.96 +O.22I+O.O2 



i I ; 



+0.641 + 1.29 +0.451 +0.85 +0.27 



—1.87 

 —0.37 

 —0.51 



-1.28—0.64—0.37- 



—0.14 

 —0.51 



—0.21+0.09 

 —0.07—0.24 



+0.07 

 —0.13 



+ 2.24—0.33—0.97 



+0.22—1.13—1.28 



i i 



+0.47:— 0.15— 0.83 



— 0.96|— 0.29 

 1.33—0.96 

 1.291-1.41 



The number of cases three days ahead were: above normal, 103; normal, 189; below normal, 73. Four days 

 ahead they were: above normal, 100; normal, 209; below normal, 54. Five days ahead they were: above 

 normal, 78; normal, 223; below normal, 59. 



A summary of the results for the days for which the forecasts 

 were made is as follows : 



Table i8. — Summary of Verifications of 3- to 5-day Forecasts. 



Temperature forecast High Normal Low High-Low 



3 days ahead of data +1.6 — 0.6 — i.o +2.6 



4 days ahead of data -fi.o — 0.2 — 1.3 +2.3 



5 days ahead of data +0.5 — o.i — 0.8 +1.3* 



^The ditTerence between the mean temperature following forecasts of high temperature 

 five days in advance and that following forecasts of low temperature for the seven months 

 Dec. 1924 to May 1925 is 2°.i, showing increasing accuracy in the forecasts with increasing 

 knowledge. 



The mean results for the weekly and monthly forecasts were as 

 follows : 



Table 19. — Verification of Weekly and Monthly Forecasts of 

 Mean Maximum Temperature. 



Above 

 Temperature forecast normal 



For the week, from 3 days ahead of 



week's beginning +0. 37 



For the month, from 3 days ahead of 



month's beginning +0.16 



At first the 3- to 5-day forecasts were based largely on the relations 

 shown in figures 2 and 3, later these were supplemented by direct 

 observations of the sun and the relations shown in figures 38 and 39 



