RADIOACTIVITY IN PRECIPITATION
passing over the
933
rain-gauge network of the Agricultural Research
Service of the U. 8. Department of Agriculture. This network is located
in central Oklahoma within the “beta” network of the Weather Bureau’s
National Severe Storms Laboratory (NSSL) and under surveillance by
the NSSL WSR-57 radar. Time-rainfall collections were made for all
storms investigated over the network shownin Fig. 1.
N
1
e
NSSL
2
°
3
e
4
6
7
&
WSR-57 RADAR
0
5 10
errr!
3eo
NAUTICAL MILES
e
°
8
9
e
10
e
Fig. 1—Network of automatic rainfall collectors.
ANALYSIS OF STORM OF APRIL 17
The surface synoptic chart for 0000Z,
Fig. 2, shows a strong
cyclone system over Minnesota, with a cold front extending southwestward through South Dakota, Wyoming, Utah, and Nevada, At this
time and during the storm period, Oklahoma was influenced by gen-
erally southwesterly flow through the troposphere. The convective
cells that developed into a short squall line were well ahead of the
surface front.
The squall line, oriented northeast—southwest and moving eastward at 20 knots, was about 40 nautical miles long and 20 nautical
miles wide when the southernmost cell appeared over station l.
Figure 3 shows the position and intensity of the cell at this time.
The maximum intensity, 48 db, was maintained as the storm continued
eastward over the network.
A time sequence of the positions of the
area of maximum intensity of the cell, Fig. 4, shows that the maximum-
intensity area increases from 0020 to 0033 CST and then decreases to
0046 CST. This cycle is repeated from 0046 to 0125 CST. During these
cycles station 1 was beneath a portion of the storm-cell cloud mass.