Vol. IX, Nos. 8-9.j Nor’ westers and Monsoon Prediction. 309 
[N.8.] 
in the cloud canopy, sometimes of an impressive nature. In 
such cases there is often, but by no means always, a recrudes- 
cence of the storm late in the same evening or very early next 
mornin Nor’westers will sometimes come from other 
even from the south, in 66 case the distinguishing feature 
being the presence of the wave or waves of cloud moving for- 
ward rapidly, but with a rapid transverse motion as well. e 
transverse movement, also is occasionally from east to west, 
but in such cases the nor’ wester is of very feeble strength. 
Its FoRMATION. 
n considering the formation of the storm one must 
Bese for the wind, temperature and vapour tension noted 
North. 
pad Sane % South. 
nN hint 
a 4 ia 
nee 
ht a 
A. First storm cloud, moving eno from W.S.W. to E.N.E. and 
trav mgt towards south south-eas 
Area of descending catbiale: winds “clear with a few cloud eddies 
which ss anatase in the cold dr 
C. Main cloud mass, of which the adeait ancing surface has very definite 
outline owing to great difference in temperature and humidity of 
the air-currents. 
a. Southerly wind from Bay. 
b. Still air layer between a and c. 
c. Upper northerly win 
d, First up-current of lower heated a 
e. Dust storm at ground level at pone of the two currents. 
fj. Heavy r 
g. Upper se wind deflected downwards to pass under main cloud 
h. Lightning usually occurs most plentifully at this ae in the cloud— 
seldom cloud to earth, which if it occurs takes at f. 
= Sir John Eliot, and also for the transverse motion and the 
urious double layer of nse ara clouds with a stretch of com- 
paratively clear sky between. My own view is that the storm 
begins in the first bank "of clouds. In any hot country 
where the — _ lower layer of - is heated to a high 
temperature by the sun there must always be a condition 
of veiled instability desiee the daytime between the light 
