88 PAULINE M. AUSTIN 
boil _j 
° 10 20 MILES 
Fic. 2—Irregular rain pattern and narrow bands in later period of storm at 03h00m EST, 
October 19, 1957 
already been described and may be summarized 
as follows: 
(1) Synoptic scale storm with low pressure 
center in one case in the Great Lakes region, and 
in the other over Hudson Bay, but in both cases 
with a north-south cold front well to the west of 
the station and a warm front to the south. 
(2) Mesoscale areas of precipitation consisting 
of a poorly defined area of light rain containing 
only a few heavy showers, then a well-defined 
broad band containing the heaviest rain, and 
finally several smaller narrower bands. 
(3) Areas of heavy rain within the bands 
whose spacing and dimensions are on the order 
of 30-50 mi. 
(4) Individual convective showers which are 
about two to five miles in horizontal dimension 
and 15,000 to 20,000 ft in height. 
Motions of storm areas—The areas of heavier 
rain, labelled B, C, D in Figure 1, and the indi- 
vidual showers as indicated by small closed con- 
tours moved in a very orderly fashion from south- 
west to northeast. In the two storms studied in 
detail most of the rain areas seemed to develop 
or move into radar range at one of two preferred 
azimuths, roughly due west or southwest. Those 
appearing in the west often had a slightly more 
westerly component to their motions than those 
in the southwest, so that they combined to form 
a north-south band (Fig. 3). 
The velocities of the rain areas were in general 
agreement with the middle-level winds which 
were nearly uniform between 5000 and 18,000 ft. 
The large intervals in time and space between 
radiosonde soundings and the uncertainties in 
the wind measurements make it impossible to de- 
