334 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



6 KILOMETERS 



SauftS^ Marie 

 MICH. 



Nashville 

 TENN. 



-1- 



Pensacola Miami 



FLA. FLA. 



i j- 



Figure 9.— Cross-section of air masses and fronts, north to south, at 8 a. m., January 22, 1937. (Courtesy 

 Massachusetts Institute of Technology.) Warm and cold fronts shown by conventional symbols; Nrp, 

 modified polar Pacific air; Pc, polar continental air; Tg, tropical Qulf air; Ts, tropical superior air. 



Table 2. — Wind Directions and Daily Rainfalls in the Ohio and Lower Mississippi 



Valleys, January 1937 

 [In inches, during 24 hours ending at 8 a. m., 75th Meridian Time] 



Although heavy rains occurred early in the month, it was not until 

 the 14th that excessive precipitation fell over the Ohio basin. This 

 precipitation came in advance of a slowly moving cold front, which by 

 the 15th had pushed eastward to the crest of the Appalachians and so 

 completed a considerable lifting of a large body of moist tropical air. 

 A day of fair weather with northwest to north winds ensued (see 

 table 2); but by the 17th the tropical w T ind had again established 

 itself over the region. Another cold front soon lifted this tropical 

 wind and squeezed it against the Appalachians again, producing 

 heavy rain on the 17 th and 18th, followed by northwest winds and 



