526
SAUCIER, HALL, AND NELSON
‘
Y
50
25
“S10
50
Fig. 1— Tornadoes observed during the 40-year period of 1916 to 1955.
Isopleths are based on total number by two-degree squares, counting
the first point of contact with ground_of 7206 tornadoes. (U.S. Weather
Bureau Chart, revised April 1960).
the three-month period from mid-March to mid-June, we are able to
observe all the types of rainfall systems with which we need be concerned. Figure 2 is an example of a weather situation that produces
intense squall-line thunderstorm activity in the general geographical
region in which Oklahoma is located. The squall line is located some
distance ahead of the cold front in the warm moist air characterized by
some convective instability.
FACILITY AND PROCEDURE
Figure 3 shows the Beta Surface Network of stations over south-
central Oklahoma. On the average, they are about 12 by 18 miles apart.
The network was expanded westward from the original 36 stations to
47 stations in the last two years to include most of the Agricultural
Research Service (ARS) network of recording rain gauges. The ARS
network is outlined by an irregular dashed line marking a watershed
boundary. In this figure Oklahoma City is located slightly to the north
of the Beta Surface Network, and Norman is at station No. 4. Each
station in the network produces continuous records of rainfall, wind
direction and speed, barometric pressure, temperature, and relative