40 JEROME NAMIAS 
<—o 
N - \Tracks of Centers of Cyclones at Sea Level, January 1959. 
Fie. 8—Cyclone tracks for January 1959; upper figures give date, lower figures central pressure 
cipitation-free area. Also in central and east 
Texas no precipitation is occurring under ascend- 
ing motions. On the 22nd there is a large pre- 
cipitation-free area to the southeast of the cy- 
clone where the upward motions are almost as 
vigorous as in the rain areas. From this and other 
similar comparisons it must be realized that our 
present understanding of the vertical motion 
field, including how to measure it (let alone pre- 
dict it) is very incomplete. Nevertheless, these 
computations represent a great step forward from 
the often vague qualitative reasoning of only a 
decade ago. Then again, it should be noted that 
upward vertical motion alone does not necessarily 
imply precipitation. The air masses partaking in 
the lifting may be too dry or too stable. It is also 
possible that the nature of nuclei of condensation 
must be considered. These considerations high- 
light the great importance of further quantitative 
studies relating vertical motion, stability, and 
moisture to precipitation, for only when the im- 
pact of these obviously significant factors are 
isolated will it be possible to evaluate the roles 
of other possible influences. 
Before closing this report, we should comment 
on the diverse nature of the precipitations 
spawned by the January storm. On the 21st, for 
example, we observe: (1) continuous snow in a 
broad belt some distance west of the cyclone 
(overrunning of Arctic by maritime tropical air) ; 
