FLOODS BEOOKS AND THIESSEN 341 



with the mixing of very cold polar air with fresh tropical air in Texas, 

 Oklahoma, and Arkansas. Here again, as in 1937, 1913, and 1882, 

 the coldness of the polar air was preserved by the deep snows not 

 far to the north. The snowfall in April 1927 was tremendous on the 

 northern Great Plains, as much as 60 inches south of the Black Hills. 

 The cold front frequently stalled in the Ouachita or in the Ozark 

 Mountains, as if the slight obstruction here was responsible for holding 

 the slowly moving front. A quasi-stationary cold front here on April 

 19-21 yielded 5 to 12 inches of rainfall. Another period of nearly 

 continuous rainfall was April 7-16. Analysis of the immediate cause 

 of the rainfall showed that convergence in south winds was answerable 

 for 43 percent, ascent over a warm front with northeast winds at the 

 surface for 35 percent, and ascent over a cold front with northwest 

 winds at the surface for 22 percent. 23 



The floods of May 1903 and of June 1915 in the lower Missouri, 

 affecting Kansas City chiefly, were due to the northward thrust of 

 tropical air by a high in the southeastern states and a westward or 

 southwestward thrust of polar air from standing highs in the Lake 

 region and westward. Lows stalled over the central plains and yielded 

 tremendous quantities of rainfall in the form of great showers. 24 



FLOODS CAUSED IN PART BY OROGRAPHIC RAINFALL: 

 APPALACHIAN AND NORTHEASTERN FLOODS OF MARCH, 1936" 



In the floods of March 1936 the Appalachian barrier seemed to play 

 an important role by forming the divide between banked-up polar air 

 on the west and tropical or its underlying modified polar Pacific or 

 polar continental air masses on the east. While this favored fairly 

 continuous rain, glaze, sleet, and snow in successive belts westward 

 from the divide, heavy rains fell on the east of the divide as fronts 

 nosed northeastward under the strong tropical wind from the south- 

 east. 26 Extraordinary rains fell where the action of these fronts was 

 augmented by such pronounced obstructions as the White Mountains. 

 Thus at Pinkham Notch, at 2,000 feet on the southeast slope of Mount 

 Washington, N. H., which rises 4,300 feet above it, 6.46 inches of rain 

 fell on March 12, while the wind on Mount Washington reached a 



»> Brooks, C. F. land N. H. Bangs], [The causes of the flooding rains of April 1927] in discussion of Flood 

 control with special reference to the Mississippi River, Proc Amer. Soc. Civil Engineers, vol. 64, pt. I, 

 pp. 1260-1265, 1928; Trans. A. S. C. E., vol. 93, pp. 894-898, 1929. 



« Frankenfleld, H. C, Floods of the spring of 1903 in the Mississippi Watershed, U. S. Weather Bur. 

 Bull. M, 1904; Day, P. O., The weather of the month [May 1915], Monthly Weather Rev., vol. 43, pp. 

 250-252, 1915; Henry, A. J., The floods of May and June, 1915, in the Missouri Valley, ibid., pp. 286-287; 

 Connor, P., Loss by floods in Kansas River and tributaries, June 1915, ibid., pp. 287-288; Henry, A. J., 

 Rivers and floods, July 1915, ibid., pp. 353-355. 



« Cf. U. S. Geological Survey; Water-Supply Papers 798, 799, and 800; The flood of March 1936; 466, 380» 

 and 351 pp. 



10 Byers, H. R., Meteorological conditions during the March 1936, and other notable floods, Journ. New 

 England Water Works Assoc, vol. 51, pp. 213-218, 9 figs., 1937. 



Lichtblau, Stephen, Weather associated with floods of March 1936, U. S. Geological Survey Water-Supply 

 Paper 800, pp. 12-31. 



