Vol. IX, Nos. 8-9.] Nor’ westers and Monsoon Prediction. 31% 
[NV.8.] 
The second deduction is equally important. This nucleus 
of the first bank of clouds is carried to the west and with it is 
carried the upper part of the column of air that feeds it from 
below. This creates a similar tendency towards an upward 
movement in the lower air to the west. This is emphasized by 
the deflection of the cold wind downwards which so increases 
the pressure on the lower air as to force it upwards. The up- 
ward and south, but actually creates a similar upthrust on its 
westerly side. What happens is that the surface—or rather, the 
layer—of still air separating the lower south wind and the upper 
north wind is being slit rapidly as the storm travels south-east. 
Fresh storm material is being formed there during the motion 
of the storm. It is this which explains the unusually rapid 
motion of the storm across the sky. 
Three motions therefore exist. There is first the general 
is 
it should easily afford information of its height. The structure 
of the bank and of the main cloud will afford evidence of the 
depth of the boundary layer and the conditions prevailing in 
the upper current. 
Speaking generally one would expect that if the upper 
northerly current is, on the average, above its normal strength 
the advance of the monsoon current will be delayed. But if it 
is above its usual strength it will probably be colder and 
