10 
small high in the interior of the convective sys- 
tem, thereby preventing the formation of any 
cyclone. Instead, a low-pressure trough 
formed just outside this small circulation wheel, 
as shown lately im detailed studies by Dr. 
Fusira—The lowest row of Figure 1 displays 
two kinds of orographic cloud and precipitation 
systems, the high-reaching and the low one, and 
also the frontal precipitation mechanism. How- 
ever, integrated over the whole globe these three 
mechanisms give much less precipitation than 
the mechanisms of the three upper rows——The 
next figures give examples of the mechanisms 
in Figure 1. 
The synoptic map of the eastern United States 
1s 
105° W 
-2 
SS 
N 
2 
X 
S 
06 LOOT ca wo/ 1010 
TOR BERGERON 
(Fig. 2) shows a convective system that is bor- 
dered at the eastern edge by what you eall a 
‘squall line’. This is, in fact, a pseudo-cold front 
since the cold air is produced by the intense 
rain-cooling caused by the convective system 
that has formed within the tropical-air warm- 
sector of a cyclone. The main precipitation of 
this cyclone came from that exceedingly impor- 
tant mechanism. When, in 1947, I first had made 
the analysis shown in the cross section of Figure 
1, second row, I ‘forecast’ that the maximum 
precipitation intensity would occur along the 
leading edge of this convective system, followed 
by a minimum in the interior because of cloud 
decay caused by the rain-cooling there; then 
2 June 1951, 00h30™z 
Pu JN=0 Cloudless 
+2--—— _ Ground 
ereee © >24km 
alt. 
Pseudo-coldfront (and isobar) 
Pressure -jump line 
3-hourly isallobar 
Fictitious isobar 
Precip. area at synoptic hour 
Isohyetal ee within 
A. 9 
12, Shen 
\ 
central 
7 
° 
i 12) 95 
region 
S//2 
3. 5a—Convective system, June 2, 1951, 00h 30m 
