488 Eighth Annual Report of the 



Thunderstorms. 



Summer rains in New Yoi'k occur to a large extent as thunder- 

 storms, and generally the regions showing pronounced summer 

 maxima are very subject to these electrical disturbances. 



The summer of 1892 was remarkable for the frequent oi-r-ur- 

 rence of thunderstorms over the northeastern States, and an in- 

 vestigation which was then undertaken with the aid O'f numerous 

 voluntary observers has furnished information of value as bear- 

 ing upon the distribution of rainfall over New York. A prelim- 

 inary study of the data has shown, first, that thunderstorms 

 develop most frequently in the brioken or mountainous sections 

 of the State, and especially in the highlands near the Pennsyl- 

 vania border and Lake Erie, the Catskill and adjacent mountain 

 ranges, and in the eastern portion of the Adirondack plateau. 

 Regions of less frequent oTiginatioin are found near the shore of 

 Lake Ontario', in the St. Lawrence valley and on the Atlantic 

 coast. 



In all parts of the State the storms move in a generally easterly 

 course, showing, however, considerable divergencies from this 

 direction which are in some degree characteristic of different 

 regions of the State. Thus, in western New York and the St. 

 Lawrence valley the usual mravement is to^^rd the north of east, 

 in the central part of the State nearly east, while in the Hudson 

 and Champlain valleys, a southerly component is more frequently 

 found. The average rate of motion^ of thunderstorms in this 

 State is about thirty miles per hour; the maximum velocity thus 

 fariobserved being about fifty miles per hour. 



The storms which oa'iginate in the southwestern section appear 

 in most cases to die out on the middle slopes of the western 

 plateau, and do not often continue their course to the region of 

 Lake Ontario. Hence, the region stretching from northern Erie 

 county eastward to the lower ends O'f the Central Lakes is one of 

 minimum sticrm frequency, and has a light annual rainfall. The 

 central part of the eastern plateau, on the other hand, appears to 

 derive a considerable projwrtioni of its storms from the section 

 south of the Central Lakes and near the Pennsylvania border. 



