T. Russell — Prediction of Cold-waves. 463 



Art. LIX. — Prediction of Cold-waves from Signal Service 

 Weather Maps ; by T. Kussell. 



[Read before the American Association for the Advancement of Science, at 

 Indianapolis, August 25, 1890, by T. Russell, Assistant Professor, Signal Service.] 



In addition to the regular fall of temperature that takes place 

 from day to night, there are irregular falls occurring from 

 time to time. The extent of country covered by these falls is 

 various at different times. When the fall of temperature in 

 twenty-four hours is twenty degrees or more and covers an area 

 of at least fifty thousand square miles and the temperature in 

 any part of the area goes as low as 36° it is called a cold-wave. 

 Answering to this definition, there have been in the United 

 States in the past ten years, 1880 to 1890, six hundred and 

 twenty-one cold- waves, as shown by the 7 A. m. weather-maps 

 of the Signal Service. 



In Table I, is given the number of cold-waves, of various ex- 

 tents, according to the area enclosed by the twenty-degree 

 temperature-fall line, that have occurred in ten years, in the 

 months of October, November, December, January, February 

 and March. 



Table I. 



Number of cold-waves, 1880 to 1890, according to extent of twenty-degree temperature-fall areas. 



T 50.000 100,000 200,000 300,000 400,000 500,000 600.000 700,000 800,000 900,000 1,000,000 1,100,000 



,, e L to to to to to to to to to to to to 



AlonttiB. 100,000. 200,000. 300.000. 400,000. 500,000. 600,000. 700,000. 800,000. 900,000. 1,000,000. 1,100,000. 1,200,000. 



January 13 27 25 29 16 13 9 4 3 1 1 2 



February. 23 26 19 24 13 10 6 5 2 2 2 1 



March.*.. 30 24 13 11 12 1 2 1 1 



October.. 21 13 2 1 1 



November 32 14 12 10 8 5 1 .. 1 2 



December 3L 30 21 16 14 5 1 3 5 1 



Sums.. 150 134 92 91 64 34 19 13 12 6 3 3 



The greatest cold-wave was that of January 17, 1882. The 

 twenty-degree fall line included an area of 1,101,000 square 

 miles, and the ten-degree fall line an area of 2,929,000 square 

 miles. There have been in ten years six cold-waves with the 

 area of the twenty-degree fall greater than one million square 

 miles. The magnitude of maximum temperature-fall in cold- 

 waves varies greatly at different times. The different curves 

 of temperature-fall lie one within the other, the twenty-degree 

 within the ten-degree, the thirty within the twenty and so on. 

 There is a gradual increase of temperature-fall from the border 

 of a cold-wave area to the center which is the place of maxi- 

 mum-fall. There have been two cases in ten years where the 

 maximum fall was over sixty degrees, the greatest being sixty- 

 three. There were sixteen cases where the maximum fall was 

 between fifty and sixty degrees ; seventy-seven cases with the 



