THE COLD-WAVES OF SOUTH-CENTRAL WISCONSIN. 
JAMES L. BARTLETT. 
Of all the atmospheric phenomena attending winter storms 
the cold-wave is the most noteworthy. The term was origin¬ 
ated many years ago by the United States Signal Corps to 
signify a marked fall in temperature rather than the occurrence 
of extreme cold. As used at present by the Weather Bureau 
it is understood to mean a decrease in temperature of 20° * in 
24 hours, independent of the regular diurnal change, to or be¬ 
low a certain fixed minimum which varies from zero during 
the winter months in western Wisconsin to 24° in the eastern 
portion of the state during the remainder of the year. The 
reason for this variation of the minimum is to limit the official 
cold-wave to a phenomenon of economic importance. In this 
paper the subject will be discussed from a meteorological point 
of view. 
The meteorological cold-wave consists of an abnormal tem¬ 
perature fall, occurring usually in the western quadrants of a 
cyclonic storm area, during the colder months, and generally 
attended by high north to west winds, increasing barometric 
pressure and clearing weather. The foregoing atmospheric 
conditions of course occur during all seasons of the year, their 
frequency depending almost wholly upon the frequency of the 
passage of cyclonic storms. Bor example, in Table 1 the sec¬ 
ond curve shows the sharp temperature fall attending the 
thunder-squall between 2 p. m. and 4 p. m. of June 1, 1905. 
This fall in temperature corresponds, for the summer months, 
1 Temperatures in this paper are in the English or Fahrenheit scale. 
