V - Missouri Department of Natural Resources

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estimates and flood photographs were furnished by the Corps of Engineers. Flood profiles were
prepared jointly by the Corps of Engineers and U. S. Geological Survey. Streamflow data collec·
tion was done by the U. S. Geological Survey with the financial cooperation of the 1'11550u[1
Geological Survey and Water Resources, the Corps of Engineers, and the Missouri State Highway
Commission.
DESCRIPTION OF STOR!'IS
Meteorological Conditions by U. S. Weather Bureau
The meteorological conditions prevailing in the lower atmosphere during the flood period
are shown by the charts in figure 2. which depict conditions on the 850 millibar (mb) surface.
This level is about 4,000 feet above ground in northwestern Missouri. It will be seen that a
quasi-stationary low center was located in the vicinity of Colorado and a quasi-stationary high
was over or near Arkansas. A cold migratory high center moved down from Canada snd across Lake
Michigan. To the south of the front a strong south-southwesterly low-level flow prevailed
across Kansas and Oklahoma which prOVided an abundant moisture supply from the Gulf of Mexico,
a necessary condition for heavy rain in the central United States. The front served as a
"trigger" mechanism to induce a convergence of the low-level water vapor transport in the rain
area..
The surface temperature contrast across the front was quite marked. Mid-afternoon temper­
atures on July 18 and 19 were in the upper 90's and lower 100's in south-central and southeast­
ern Kansas. Afternoon temperatures to the north of the front were in the upper 70's and lower
80's on July 18 and even cooler July 19 when they were in the lower 70's in northern Missouri
and in Iowa. The 850 mb isotherms (dotted lines) in figure 2 also indicate a strong tempera­
ture gradient. Cloudiness and cooling by evaporation of falling raindrops to the north of the
surface position of the front helped to maintain this temperature contrast. The rain area may
be considered to have had a tendency toward self-perpetuation, in the sense that rain and
clouds helped to maLntain a temperature gradient favorable for further rain.
Slowly-changing weather situations such as rhis one are more likely to be flood-producing
for the reason that the rainfall is concentrated in a small area, rather than being spread over
a larger area, as it would be in a more rapidly-moving situation. Steering-level winds (10,000
ft and up) were light west-northwesterly and radar data show that precipitation echoes in the
rain area moved generally in an east-southeasterly direction at 15-25 knots (l knot = 1.15
miles per hour). TIlere was a persistent regeneration of echoes upstream in the steering-level