Weather is Major Consideration. The single, major factor at zero hour or any time following zero hour with regard both to suc- cessful conduct of the technical operation and to blast and radiation fallout is weather, The obtaining of scientific data, the operations of a bombing plane and scores of other aircraft, the direction'and intensity of blast, the success of the troop operation, and the direction and intensity of radioactive fallout are all dependent on such factors as precipitation, cloud cover, temperature, temperature inversions, and wind directions and velocities. It is essential that forecasters predict within smal’ margins of error the direction and velocities of winds from ground surface upward to high altitudes. This is particularly difficult at ground surface in the mountain-surrounded basin used for a firing area where winds will cirele the compass in a few moments. To obtain comprehensive data, the U. S. Air Force Weather Service has established a weather unit at NTS, into which personnel of the U. S. Weather Bureau are integrated. It receives reports on hemispheric conditions and on more localized conditions. To | further pinpoint conditions locally, a network of stations has been established in a complete ring around the Test Site. These are lo- t cated at Kingman, Arizona; Baker and Edwards Air Force Base, California; St. George, Utah; and Indian Springs, Beatty, Tonopah, Reno, Austin, Lincoln Mine, Caliente and Overton, Nevada. Additionally, U. S. Weather Bureau stations at Bishop, California; Milford, Utah; and Ely, Las Vegas and Winnemucca, Nevada, will provide local information to the NTS weather unit as required. Other U. S. Weather Bureau and USAF stations will supply supplemental data on request. New procedures have been adcpted to facilitate more accurate forecasting of wind directions and velocities at zero hour and for several hours thereafter. weather conditions become progressively more important as shot hour approaches. An important factor is the final weather forecast, available at about minus one hour. It determines whether the test is to be fired. Factors Affecting Last Minute Postponements Thereare actually a considerable number of reasons for postponing a shct even after the evening evaluation meeting has decided to go ahead. Some, but not all, of these are discussed. It is seldom that all of the multitude of experiments are satisfied on a shot -- because they were not ready, because of malfunctioning, or because of weather and shot effects. A shot is not fired, -17fs. Or. . ‘\ Le DT LP way Forts,