WMOD00297

• Title: Hygroscopic Seeding in Oklahoma
• Date: 10/31/1971
• State: OK
• Weather Modification - Doc Type: Report

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A Summary of Events

This program involved utilizing large systems under difficult field
conditions. and doing it all on a rush basis. with a very small crew
being dictated by funding limitations. The work was on a best-efforts
basis. since the program was too small to permit the use of backup
crews and equipment to give complete reliability. As it turned out. the
program was able to take advantage of the best weather for seeding;
through luck as well as very hard work. installations and maintenance
were able to be handled during periods which were not suitable for
seeding. The difficulty of forecasting the likelihood of seedable clouds
in the limited target area made the work difficult. Being II on callll meant
preparing the aircraft for flight and then securing it daily. and not being
able to schedule equipment modifications and maintenance which would
take more than an hour or two. The period of August 23 - September 8
turned out to be virtually the only time nature provided locally the sort
of convective clouds amenable to responses from seeding. This included
. the start of the period of major precipitation in Oklahoma this summer.
The precipitation then continued with largely stratified storms making
September a record month for precipitation in the state.

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Active program preparations bega!1 about August 5. During the week of
August 8-14. FTR planned all program details, prepared the C-97.
organized the crew. and expedited the paperwork associated with the FAA,
the equipment loan from Edwards Air Force Base. and obtaining of
services at Altus AFB. In addition. auxiliary apparatus for airborne
operation of the spray rig was assembled. A complete substitute nozzle
system (30 nozzles) was built when it began appearing likely that the
Air Force nozzle system might not be available immediately due to a
sudden Air Force requirement.

On August 16 official permission was received from the Air Force for
the spray rig to be made available to the Bureau of Reclamation for this
program. and the C-97 was flown to Edwards AFB to initiate picking up
the apparatus. On August 17 the loading was completed and the C-97 was
flown to Altus AFB. During a series of cloudless days the spray rig was
modified and tested, with a test flight occurring on August 21. August 22
was made a rest day which was deemed necessary to keep the flight crew
(which also handled equipment installation and maintenance) rested enough
to handle their flight duties safely.

On August 23. the first hygroscopic seeding operation took place - - associated
with a large. organized storm near Norman. The next day the C-97 seeded
an area of small cells far to the north. in an operation coordinated with the

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