Skptembeb 24, 1920] 



SCIENCE 



293 



who are able to appreciate the nature and 

 value of the work of that band of British sci- 

 entific heroes, without whose efforts, the result 

 of long years of patient training in research, 

 the war would inevitably have been lost, on 

 the land, on the sea, and in the air. If the lay 

 press would descend from its wooden pedestal 

 and inculcate in the public mind that knowl- 

 edge and love of science through which " our 

 men of science" — unexcelled in the whole 

 world — acquired their equipment for winning 

 the war, instead of perpetuating the silly and 

 antiquated notion that they are habitually im- 

 mersed in useless hobbies of no practical util- 

 ity, it would do real service to the country. — 

 The London Electrical Review. 



NOTES ON METEOROLOGY AND 

 CLIMATOLOGY 



TORNADOES 



A FEW weeks ago an official of the Weather 

 Bureau was asked this question: How many 

 tornadoes will a healthy cyclone hatch in a 

 day? This, naturally, was a difficult question 

 to answer; but it must be admitted that the 

 tornadoes of March 28, in the middle western 

 and southern states, and those of April 20 in 

 Mississippi, Alabama and Tennessee, afford 

 striking examples of the fecundity of baro- 

 metric depressions when other conditions are 

 favorable. The Monthly Weather Review^ for 

 April, 1920, contains about 18 papers, discus- 

 sions, and notes concerning these very de- 

 structive tornadoes, as well as those which oc- 

 curred in North Carolina and Oklahoma on 

 April 12 and May 2, respectively. 



Eleven of the thirteen tornadoes of March 

 28 occurred in the region surrounding lower 

 Lake Michigan and two occurred in western 

 Alabama and eastern Georgia. It appears that 

 they were associated with the passage of the 

 squall front or line of wind-convergence which 

 marked the barrier, in the southeastern quad- 

 rant of the deep " low," between southeasterly 

 and southwesterly winds. The " low " which 



1 Papers on tornadoes, pp. 191-213. Reprints of 

 these papers may be obtained upon application to 

 the Chief, United States Weather Bureau, Wash- 

 ington, D. C. 



gave rise to this wind-shift line moved from 

 east-central Nebraska to northern Wisconsin 

 in the course of the day. In the region of 

 lower Lake Michigan, it was possible to trace 

 the hourly progress of the line as it advanced 

 on a slightly curved front in a general east- 

 northeasterly direction. It appeared at 6 a.m. 

 in northeastern Missouri and southeastern 

 Iowa; at noon, it extended along the eastern 

 line of Illinois northward to the lake, thence 

 curving northwestward into Wisconsin; at 9 

 P.M., it had almost reached Lake Huron, and 

 was over the western end of lake Erie. As its 

 northern end reached Lake Michigan, there 

 was a perceptible forward bulge which may be 

 attributed to the decreased friction as the 

 wind advanced over the smooth water surface. 

 Regarding the circumstances under which 

 these tornadoes were formed. Dr. Charles E. 

 Brooks, in his discussion, says: 



Why did these 13 tornadoes occur on the after- 

 noon of March 28? Let us review the facts as 

 brought out by the weather observations: 



1. There were strong, unusually warm winds 

 from the southeast and south-southeast over a large 

 area from the Gulf of Mexico to the Great Lakes. 



2. A well-marked line . . . separated these winds 

 from still stronger, but slightly cooler southwest or 

 south-southwest winds in a belt immediately to the 

 west. 



3. Heavy thunderstorms, some with tornadoes 

 and hail, occurred along this line of converging 

 winds. 



4. Immediately to the west of the northern por- 

 tion of this line was a belt of diverging winds, 

 characterized by brilliantly clear skies and ex- 

 ceedingly dry air, the driest on record at some 

 stations, ... 



5. Kite observations indicated the presence of a 

 cold southwest-west wind at a moderate height 

 overrunning the warm surface wind. 



6. The northeasterly movement of the tornados 

 and lower clouds and the fall of hail on or to the 

 east of the tornado paths indicated a southwest to, 

 at least, west-southwest wind not fax aloft. 



Surely this was an unusual set of conditions. 

 With winds meeting at an angle of about 60° and 

 at a rate of about 30 miles an hour, large volumes 

 of air were sent upward and given a counter- 

 clockwise rotary motion by the thrusts of the south- 

 west squalls routing under the rear portions of the 



