48 Ai.Kiei'i.n kal Manual 



over a mile in length. Many trees were uprooted or twisted off 

 and a number of houses were destroyed, but there was no loss of 

 life. Tornadoes occurred in Monroe and Steuben counties in 

 June, 1906. 



WINDS 



The prevailing winds of the state are westerly, generally shift- 

 ing toward the north in winter and toward the south in summer. 

 At so.me points, particularly Albany, Oswego, and Coopcrstown, 

 the southerly winds of summer persist throughout the fall and 

 even into December and January. At other points, particularly 

 in the mountainous sections, where local topographic conditions 

 control the wind direction, the prevailing direction is merely that 

 of a local current. This is the case at Ithaca, where the prevailing 

 direction for the entire year except the spring months is from the 

 southeast, due principally to the trend of the valley at the south- 

 ern end of Cayuga Lake. 



The so-called " night wind " of Cayuga Lake Valley is interest- 

 ing, and serves as an example of the effect of local topography. 

 It occurs dnrino- the summer months at times when the absence of 

 cyclonic disturbances gives full play to local influences. Com- 

 monly it sets in a few hours after sunset as a light breeze from 

 the south, and gradually increases in strength until a velocity of 

 about eight miles per hour is reached, which continues steadily 

 throughout the night. This current has its origin on the hillsides 

 at the southern end of the lake and flows northward down the 

 water courses converging into the main depression. As it moves 

 northward over the smooth surface of the lake, it is augmented by 

 the numerous cool currents that join the main stream through 

 the water courses that debouch upon the valley from either side. 



Night wind is air drainage on a large scale, the result of surface 

 cooling when the heat from the sun is withdrawn. Winds of this 

 character occur in other parts of the state where the local topo- 

 graphy is similar. 



Observations of the velocity of the wand are available only for 

 the nine regular weather bureau stations in the state. The high- 

 est velocity for the state, 96 miles per hour from the southwest, 



