BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY

Entered as second class matter at the Post Office, Worcester, Massachusetts, under Act of Aug. 24, 1912. Issued monthly except July and August. Annual subscription, $3.50; single copies of this issue, 35c. Address contributions to the Bulletin, and correspondence relating thereto, to ROBERT G. STONE, Editor Dept. of , New York University, University Heights, N. Y.

Vol. 23 JANUARY, 1942 No. 1

The Effect of Lake Erie on the Local Distribution of in (I)* JOHN T. REMICK, 2nd Lt., U. S. A. C. 620 East Ave., Lockport, N. Y. DESCRIPTIVE the roads are closed to traffic. HE TERM " FLURRIES" is The sharpness of the edge of the generally applied to the snow— snow-flurry area is variable—some- T light or heavy—that falls on the times quite diffuse and other times lee sides of the Great Lakes and very pronounced. A sharp boundary which is not caused by any apparent to the area is more likely to be the frontal activity. The prevailing wind case in the early fall than later in over the Great Lakes in winter is the winter—the reason for which from the west so whatever lake effect will be discussed later. there is should show up on the east- If the snow flurries are of much ern side of these lakes. consequence the fact should show up A low deck of is found usu- in the normal precipitation patterns ally to prevail over the area on the for the area. October-December is lee side of the lakes. A light snow the period of maximum snow flurry is generally falling. The water con- effect and March-May is a period of tent of the snow is variable—the the least effect. While the area in ratio of snow to water ranging from the vicinity of Jamestown, N. Y., 6 to 1 to 50 to 1. The average ratio has the largest amount in both is about 18 to 1 rather than the com- cases, the area bordering the lake is monly used 10 to 1 ratio. For the in the maximum precipitation area month of January 1940, 'Watertown, in the March-May period. By smooth- New York, on the eastern end of Lake ing out the isohyets Kincer1 shows Ontario had a total snowfall of 79 vividly the effect of the lake on the inches and a total precipitation normal precipitation. amounting to 2.84" or an average Monthly normals, of course, show snow/water ratio of 27 to 1 for the the effect more precisely. The October whole month. and November maps show it best Considerable wind usually accom- while the December and January maps panies the snow flurries and conse- show the effect much diminished (figs. quently much drifting takes place. 2-4). By January the lake tempera- Visibility sometimes gets so bad that ture is 32 °F and is partly ice covered. The snow flurries occur as often then 1J. B. Kincer: Seasonal distribution of in the U. S., Monthly Review, vol. as before but are too light to affect 47, 1919, pp. 624-631. the normals except on the Alleghany •From a B. S. thesis submitted at Mass. Inst. Techn., 1941, under the direction of Plateau where the orographic effect Prof. H. C. Willett. Lt. Remick is now with the Army in the Caribbean. is important. FIGS. 1-4. It will be noted that there is no pronounced general rise of the land. Although the Knapp Creek, New York—Coudersport, Pa. region is about 1400r above the level of Lake Erie this means an average rise of only about 28 feet a mile. The number of stations is sufficient in all parts of the area except between Erie and Buffalo—just where the local are most important. Seven to twelve inches of snow have sometimes fallen between Fredonia and Buffalo and yet no indication of this would be reported by any of the stations. Two of the maps (2nd part) show just such cases. In these two cases the data for amount and location of heaviest precipitation were obtained from newspaper reports. The normals as given on these charts were taken from the U. S. Climatological Data. No normals were used based on less than 10 years' data. The isohyets on the lower right hand part of the maps where little data is given were drawn from the maps appearing in the Monthly Weather Review showing the distribution of normal precipitation in eastern U. S. by months.

FRICTIONAL INFLUENCE levels. Such influence is generally First the lake must be considered assumed to extend to one kilometer. as an area of considerably less fric- The increase in velocity will mean an tional influence on the wind than the increase in the Coriolis force which land surrounding it. will deflect the wind to the right. In a westerly current of polar (Left and right in this discussion origin passing out onto the lake. The refer to an observer facing down- first effect of the decrease in surface wind.) According to Rossby and 2 friction will be an increase in the Montgomery the angle between sur- velocity of the wind in the lower face and gradient winds over a land surface such as prevails in the lake 2C.-G. Rossby and R. B. Montgomery, The region is 25° while the angle becomes Layer of Frictional Influence in Wind and Ocean Currents, Pavers in Phys. Ocean and 18° over water. The total effect on Met., M. I. T. and Woods Hole Ocean Inst., Vol. Ill, 3. the wind therefore as it travels over